144. Seidu, I; Brobbey, LK; Danquah, E; Oppong, SK; van Beuningen, D; Seidu, M; Dulvy, NK. (2022) Fishing for survival: Importance of shark fisheries for the livelihoods of coastal communities in Western Ghana.Fish Res. 246 Fishing for survival: Importance of shark fisheries for the livelihoods of coastal communities in Western Ghana
Artisanal fisheries; Fallback options; Household income; Livelihood strategies; Fishers' satisfaction
Small-scale shark fisheries support the livelihoods of a large number of coastal communities in developing countries. Shark meat comprises a cheap source of protein and is traded locally in many parts in developing countries, while the skins, oil, and fins are exported to the international market. This study addresses a gap in literature regarding the importance of elasmobranchs to key shark-fishing communities and the degree to which trade in shark products (meat and fins) vary in time and among fishing communities in Ghana. We interviewed 85 fishers and traders involved in shark fisheries in Axim, Dixcove, and Shama communities using semistructured questionnaires. Fishing was the primary source of income and accounted for 58.5% of the total household income of respondents. Other important economic activities were fish processing (16.0%), fish retailing (13.3%), and small businesses (2.5%). One-third and often two-thirds of respondents generated between 80% and 100% of their income from shark fisheries: Axim (65%), Dixcove (68%), and Shama (35%). Shark meat consumption was common among fishers and traders and represents a substantial source of protein in the diet of the study communities. Hammerhead sharks (Sphyrna spp) and Bull Shark (Carcharhinus leucas) have the most valuable fins and meat. Further, 75% and 95% of fishers and traders, respectively, see fishing and trading of shark meat as their last safety-net and, therefore, tend to be satisfied with their jobs. Non-fishing related livelihood streams including small businesses and transportation were the major fallback activities both fishers and traders preferred to rely on if there is a ban on the exploitation of sharks in Ghana. Overexploitation of these species will compromise food ecosystem functionality and security. Thus, any shark management strategy needs to urgently restraint mortality to sustainable levels, which, in the short-term, must take into consideration the preferred livelihood fallback options outlined by fishers and traders, and implement them to ensure the longterm benefits of the intervention. DOI
143. Bigman, JS; M'Gonigle, LK; Wegner, NC; Dulvy, NK. (2021) Respiratory capacity is twice as important as temperature in explaining patterns of metabolic rate across the vertebrate tree of life.Sci. Adv. 7 Respiratory capacity is twice as important as temperature in explaining patterns of metabolic rate across the vertebrate tree of life
Metabolic rate underlies a wide range of phenomena from cellular dynamics to ecosystem structure and function. Models seeking to statistically explain variation in metabolic rate across vertebrates are largely based on body size and temperature. Unexpectedly, these models overlook variation in the size of gills and lungs that acquire the oxygen needed to fuel aerobic processes. Here, we assess the importance of respiratory surface area in explaining patterns of metabolic rate across the vertebrate tree of life using a novel phylogenetic Bayesian multilevel modeling framework coupled with a species-paired dataset of metabolic rate and respiratory surface area. We reveal that respiratory surface area explains twice as much variation in metabolic rate, compared to temperature, across the vertebrate tree of life. Understanding the combination of oxygen acquisition and transport provides opportunity to understand the evolutionary history of metabolic rate and improve models that quantify the impacts of climate change. DOI PubMed
142.Dulvy, NK; Pacoureau, N; Rigby, CL; Pollom, RA; Jabado, RW; Ebert, DA; Finucci, B; Pollock, CM; Cheok, J; Derrick, DH; Herman, KB; Sherman, CS; VanderWright, WJ; Lawson, JM; Walls, RHL; Carlson, JK; Charvet, P; Bineesh, KK; Fernando, D; Ralph, GM; Matsushiba, JH; Hilton-Taylor, C; Fordham, SV; Simpfendorfer, CA. (2021) Overfishing drives over one-third of all sharks and rays toward a global extinction crisis.Curr. Biol. 31: 4773-+ Overfishing drives over one-third of all sharks and rays toward a global extinction crisis
The scale and drivers of marine biodiversity loss are being revealed by the International Union for Conservation of Nature (IUCN) Red List assessment process. We present the first global reassessment of 1,199 species in Class Chondrichthyes-sharks, rays, and chimeras. The first global assessment (in 2014) concluded that one-quarter (24%) of species were threatened. Now, 391 (32.6%) species are threatened with extinction. When this percentage of threat is applied to Data Deficient species, more than one-third (37.5%) of chondrichthyans are estimated to be threatened, with much of this change resulting from new information. Three species are Critically Endangered (Possibly Extinct), representing possibly the first globalmarine fish extinctions due to overfishing. Consequently, the chondrichthyan extinction rate is potentially 25 extinctions per million species years, comparable to that of terrestrial vertebrates. Overfishing is the universal threat affecting all 391 threatened species and is the sole threat for 67.3% of species and interacts with three other threats for the remaining third: loss and degradation of habitat (31.2% of threatened species), climate change (10.2%), and pollution (6.9%). Species are disproportionately threatened in tropical and subtropical coastal waters. Science-based limits on fishing, effective marine protected areas, and approaches that reduce or eliminate fishing mortality are urgently needed to minimize mortality of threatened species and ensure sustainable catch and trade of others. Immediate action is essential to prevent further extinctions and protect the potential for food security and ecosystem functions provided by this iconic lineage of predators. DOI PubMed
141. Finucci, B; Cheok, J; Ebert, DA; Herman, K; Kyne, PM; Dulvy, NK. (2021) Ghosts of the deep - Biodiversity, fisheries, and extinction risk of ghost sharks.Fish. Fish. 22: 391-412 Ghosts of the deep - Biodiversity, fisheries, and extinction risk of ghost sharks
by‐ catch; chimaera; chondrichthyan; data deficiency; holocephali; IUCN Red List; liver oil; sustainable fisheries
Ghost sharks (subclass Holocephali) remain a largely data-poor group of cartilaginous fishes. The general paucity of attention may partially be related to identification and unresolved taxonomic issues, occurrence in the deep oceans, and their low value and interest in fisheries (which some notable exceptions). Here, we synthesize and assess the extinction risk of all known extant ghost sharks (52 species) by applying the IUCN Red List of Threatened Species Categories and Criteria. Ghost sharks have a low proportion of threatened (8%) and Near Threatened (8%) species, with most species (69%) assessed as Least Concern. The group still exhibits some data deficiency (15%), and biological information is lacking for most species. Endemism is high, with 37% of species known from only one location or one country. Species richness was highest in the Northeast Atlantic, off the northwest coast of Africa (Morocco to Mauritania), the East China Sea, New Zealand and off the northwest coast of South America (Ecuador and Peru). Ghost sharks are predominately taken as by-catch, but some targeted fishing and/or retention for the liver oil trade occurs. Species-specific reporting, monitoring and management are required to assess population trends, and further investigation is needed on trade and use, particularly for higher risk species including the sicklefin chimaeras (genus Neoharriotta) and the American Elephantfish (Callorhynchus callorhynchus, Callorhinidae). DOI
140. Mann, ME; Hall, LJ; Dulvy, NK. (2021) Scientific impact in a changing world.Cell 184: 1407-1408 Scientific impact in a changing world
Measuring scientific success has traditionally involved numbers and statistics. However, due to an increasingly uncertain world, more than ever we need to measure the effect that science has on real-world scenarios. We asked researchers to share their points of view on what scientific impact means to them and how impact matters beyond the numbers. PubMed
139. Pacoureau, N; Rigby, CL; Kyne, PM; Sherley, RB; Winker, H; Carlson, JK; Fordham, SV; Barreto, R; Fernando, D; Francis, MP; Jabado, RW; Herman, KB; Liu, KM; Marshall, AD; Pollom, RA; Romanov, EV; Simpfendorfer, CA; Yin, JS; Kindsvater, HK; Dulvy, NK. (2021) Half a century of global decline in oceanic sharks and rays.Nature 589: 567-+ Half a century of global decline in oceanic sharks and rays
Overfishing is the primary cause of marine defaunation, yet declines in and increasing extinction risks of individual species are difficult to measure, particularly for the largest predators found in the high seas(1-3). Here we calculate two well-established indicators to track progress towards Aichi Biodiversity Targets and Sustainable Development Goals(4,5): the Living Planet Index (a measure of changes in abundance aggregated from 57 abundance time-series datasets for 18 oceanic shark and ray species) and the Red List Index (a measure of change in extinction risk calculated for all 31 oceanic species of sharks and rays). We find that, since 1970, the global abundance of oceanic sharks and rays has declined by 71% owing to an 18-fold increase in relative fishing pressure. This depletion has increased the global extinction risk to the point at which three-quarters of the species comprising this functionally important assemblage are threatened with extinction. Strict prohibitions and precautionary science-based catch limits are urgently needed to avert population collapse(6,7), avoid the disruption of ecological functions and promote species recovery(8,9). DOI PubMed
138. Prinzing, TS; Zhang, YF; Wegner, NC; Dulvy, NK. (2021) Analytical methods matter too: Establishing a framework for estimating maximum metabolic rate for fishes.Ecol. Evol. 11: 9987-10003 Analytical methods matter too: Establishing a framework for estimating maximum metabolic rate for fishes
active metabolic rate; aerobic metabolism; aquatic respirometry; elasmobranch; maximum exercise; metabolic theory
Advances in experimental design and equipment have simplified the collection of maximum metabolic rate (MMR) data for a more diverse array of water-breathing animals. However, little attention has been given to the consequences of analytical choices in the estimation of MMR. Using different analytical methods can reduce the comparability of MMR estimates across species and studies and has consequences for the burgeoning number of macroecological meta-analyses using metabolic rate data. Two key analytical choices that require standardization are the time interval, or regression window width, over which MMR is estimated, and the method used to locate that regression window within the raw oxygen depletion trace. Here, we consider the effect of both choices by estimating MMR for two shark and two salmonid species of different activity levels using multiple regression window widths and three analytical methods: rolling regression, sequential regression, and segmented regression. Shorter regression windows yielded higher metabolic rate estimates, with a risk that the shortest windows (<1-min) reflect more system noise than MMR signal. Rolling regression was the best candidate model and produced the highest MMR estimates. Sequential regression models consistently produced lower relative estimates than rolling regression models, while the segmented regression model was unable to produce consistent MMR estimates across individuals. The time-point of the MMR regression window along the oxygen consumption trace varied considerably across individuals but not across models. We show that choice of analytical method, in addition to more widely understood experimental choices, profoundly affect the resultant estimates of MMR. We recommend that researchers (1) employ a rolling regression model with a reliable regression window tailored to their experimental system and (2) explicitly report their analytical methods, including publishing raw data and code. DOI PubMed
137. Shiffman, DS; Macdonald, CC; Wallace, SS; Dulvy, NK. (2021) The role and value of science in shark conservation advocacy.Sci Rep 11 The role and value of science in shark conservation advocacy
Many species of sharks are threatened with extinction, and there has been a longstanding debate in scientific and environmental circles over the most effective and appropriate strategy to conserve and protect them. Should we allow for sustainable fisheries exploitation of species which can withstand fishing pressure, or ban all fisheries for sharks and trade in shark products? In the developing world, exploitation of fisheries resources can be essential to food security and poverty alleviation, and global management efforts are typically focused on sustainably maximizing economic benefits. This approach aligns with traditional fisheries management and the perspectives of most surveyed scientific researchers who study sharks. However, in Europe and North America, sharks are increasingly venerated as wildlife to be preserved irrespective of conservation status, resulting in growing pressure to prohibit exploitation of sharks and trade in shark products. To understand the causes and significance of this divergence in goals, we surveyed 155 shark conservation focused environmental advocates from 78 environmental non-profits, and asked three key questions: (1) where do advocates get scientific information? (2) Does all policy-relevant scientific information reach advocates? and (3) Do advocates work towards the same policy goals identified by scientific researchers? Findings suggest many environmental advocates are aware of key scientific results and use science-based arguments in their advocacy, but a small but vocal subset of advocates report that they never read the scientific literature or speak to scientists. Engagement with science appears to be a key predictor of whether advocates support sustainable management of shark fisheries or bans on shark fishing and trade in shark products. Conservation is a normative discipline, and this analysis more clearly articulates two distinct perspectives in shark conservation. Most advocates support the same evidence-based policies as academic and government scientists, while a smaller percentage are driven more by moral and ethical beliefs and may not find scientific research relevant or persuasive. We also find possible evidence that a small group of non-profits may be misrepresenting the state of the science while claiming to use science-based arguments, a concern that has been raised by surveyed scientists about the environmental community. This analysis suggests possible alternative avenues for engaging diverse stakeholders in productive discussions about shark conservation. DOI PubMed
136. Walls, RHL; Dulvy, NK. (2021) Tracking the rising extinction risk of sharks and rays in the Northeast Atlantic Ocean and Mediterranean Sea.Sci Rep 11 Tracking the rising extinction risk of sharks and rays in the Northeast Atlantic Ocean and Mediterranean Sea
The loss of biodiversity is increasingly well understood on land, but trajectories of extinction risk remain largely unknown in the ocean. We present regional Red List Indices (RLIs) to track the extinction risk of 119 Northeast Atlantic and 72 Mediterranean shark and ray species primarily threatened by overfishing. We combine two IUCN workshop assessments from 2003/2005 and 2015 with a retrospective backcast assessment for 1980. We incorporate predicted categorisations for Data Deficient species from our previously published research. The percentage of threatened species rose from 1980 to 2015 from 29 to 41% (Northeast Atlantic) and 47 to 65% (Mediterranean Sea). There are as many threatened sharks and rays in Europe as there are threatened birds, but the threat level is nearly six times greater by percentage (41%, n=56 of 136 vs. 7%, n=56 of 792). The Northeast Atlantic RLI declined by 8% from 1980 to 2015, while the higher-risk Mediterranean RLI declined by 13%. Larger-bodied, shallow-distributed, slow-growing species and those with range boundaries within the region are more likely to have worsening status in the Northeast Atlantic. Conversely, long-established, severe threat levels obscure any potential relationships between species' traits and the likelihood of worsening IUCN status in the Mediterranean Sea. These regional RLIs provide the first widespread evidence for increasing trends in regional shark and ray extinction risk and underscore that effective fisheries management is necessary to recover the ecosystem function of these predators. DOI PubMed
135. Wong, S; Bigman, JS; Dulvy, NK. (2021) The metabolic pace of life histories across fishes.Proc. R. Soc. B-Biol. Sci. 288 The metabolic pace of life histories across fishes
allometry; Bergmann's rule; gill oxygen limitation theory; metabolic theory of ecology; temperature-size rule
All life acquires energy through metabolic processes and that energy is subsequently allocated to life-sustaining functions such as survival, growth and reproduction. Thus, it has long been assumed that metabolic rate is related to the life history of an organism. Indeed, metabolic rate is commonly believed to set the pace of life by determining where an organism is situated along a fast-slow life-history continuum. However, empirical evidence of a direct interspecific relationship between metabolic rate and life histories is lacking, especially for ectothermic organisms. Here, we ask whether three life-history traits-maximum body mass, generation length and growth performance-explain variation in resting metabolic rate (RMR) across fishes. We found that growth performance, which accounts for the trade-off between growth rate and maximum body size, explained variation in RMR, yet maximum body mass and generation length did not. Our results suggest that measures of life history that encompass trade-offs between life-history traits, rather than traits in isolation, explain variation in RMR across fishes. Ultimately, understanding the relationship between metabolic rate and life history is crucial to metabolic ecology and has the potential to improve prediction of the ecological risk of data-poor species. DOI PubMed
134. Wong, SA; Bigman, JS; Yopak, KE; Dulvy, NK. (2021) Gill surface area provides a clue for the respiratory basis of brain size in the blacktip shark (Carcharhinus limbatus).J. Fish Biol. 99: 990-998 Gill surface area provides a clue for the respiratory basis of brain size in the blacktip shark (Carcharhinus limbatus)
direct metabolic constraints; expensive brain; ontogenetic allometry; oxygen limitation; temperature-size rule
Brain size varies dramatically, both within and across species, and this variation is often believed to be the result of trade-offs between the cognitive benefits of having a large brain for a given body size and the energetic cost of sustaining neural tissue. One potential consequence of having a large brain is that organisms must also meet the associated high energetic demands. Thus, a key question is whether metabolic rate correlates with brain size. However, using metabolic rate to measure energetic demand yields a relatively instantaneous and dynamic measure of energy turnover, which is incompatible with the longer evolutionary timescale of changes in brain size within and across species. Morphological traits associated with oxygen consumption, specifically gill surface area, have been shown to be correlates of oxygen demand and energy use, and thus may serve as integrated correlates of these processes, allowing us to assess whether evolutionary changes in brain size correlate with changes in longer-term oxygen demand and energy use. We tested how brain size relates to gill surface area in the blacktip shark Carcharhinus limbatus. First, we examined whether the allometric slope of brain mass (i.e., the rate that brain mass changes with body mass) is lower than the allometric slope of gill surface area across ontogeny. Second, we tested whether gill surface area explains variation in brain mass, after accounting for the effects of body mass on brain mass. We found that brain mass and gill surface area both had positive allometric slopes, with larger individuals having both larger brains and larger gill surface areas compared to smaller individuals. However, the allometric slope of brain mass was lower than the allometric slope of gill surface area, consistent with our prediction that the allometric slope of gill surface area could pose an upper limit to the allometric slope of brain mass. Finally, after accounting for body mass, individuals with larger brains tended to have larger gill surface areas. Together, our results provide clues as to how fishes may evolve and maintain large brains despite their high energetic cost, suggesting that C. limbatus individuals with a large gill surface area for their body mass may be able to support a higher energetic turnover, and, in turn, a larger brain for their body mass. DOI PubMed
133. Yan, HF; Kyne, PM; Jabado, RW; Leeney, RH; Davidson, LNK; Derrick, DH; Finucci, B; Freckleton, RP; Fordham, SV; Dulvy, NK. (2021) Overfishing and habitat loss drives range contraction of iconic marine fishes to near extinction.Sci. Adv. 7 Overfishing and habitat loss drives range contraction of iconic marine fishes to near extinction
Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now presumed extinct in more than half (n = 46). Using dynamic geography theory, we predict that sawfishes are gone from at least nine additional nations. Overfishing and habitat loss have reduced spatial occupancy, leading to local extinctions in 55 of the 90 nations, which equates to 58.7% of their historical distribution. Retention bans and habitat protections are urgently necessary to secure a future for sawfishes and similar species. DOI PubMed
132. Derrick, DH; Cheok, J; Dulvy, NK. (2020) Spatially congruent sites of importance for global shark and ray biodiversity.PLoS One 15 Spatially congruent sites of importance for global shark and ray biodiversity
Many important areas identified for conservation priorities focus on areas of high species richness, however, it is unclear whether these areas change depending on what aspect of richness is considered (e.g. evolutionary distinctiveness, endemicity, or threatened species). Furthermore, little is known of the extent of spatial congruency between biodiversity measures in the marine realm. Here, we used the distribution maps of all known marine sharks, rays, and chimaeras (class Chondrichthyes) to examine the extent of spatial congruency across the hotspots of three measures of species richness: total number of species, evolutionarily distinct species, and endemic species. We assessed the spatial congruency between hotspots considering all species, as well as on the subset of the threatened species only. We consider three definitions of hotspot (2.5%, 5%, and 10% of cells with the highest numbers of species) and three levels of spatial resolution (1 degrees, 4 degrees, and 8 degrees grid cells). Overall, we found low congruency among all three measures of species richness, with the threatened species comprising a smaller subset of the overall species patterns irrespective of hotspot definition. Areas of congruency at 1 degrees and 5% richest cells contain over half (64%) of all sharks and rays and occurred off the coasts of: (1) Northern Mexico Gulf of California, (2) USA Gulf of Mexico, (3) Ecuador, (4) Uruguay and southern Brazil, (5) South Africa, southern Mozambique, and southern Namibia, (6) Japan, Taiwan, and parts of southern China, and (7) eastern and western Australia. Coarsening resolution increases congruency two-fold for all species but remains relatively low for threatened measures, and geographic locations of congruent areas also change. Finally, for pairwise comparisons of biodiversity measures, evolutionarily distinct species richness had the highest overlap with total species richness regardless of resolution or definition of hotspot. We suggest that focusing conservation attention solely on areas of high total species richness will not necessarily contribute efforts towards species that are most at risk, nor will it protect other important dimensions of species richness.Website DOI PubMed
131.Dulvy, NK; Yan, HF. (2020) Conservation: Goldilocks Nations for Restoring Reef Sharks.Curr. Biol. 30: R1415-R1418 Conservation: Goldilocks Nations for Restoring Reef Sharks
The first baited, video-based global survey of coral reef sharks reveals widespread depletion and functional extinction from eight nations. The authors identify priority 'Goldilocks' nations with the necessary combination of governance and shark abundance to recover depleted shark populations. DOI PubMed
130. Kyne, PM; Jabado, RW; Rigby, CL; Dharmadi; Gore, MA; Pollock, CM; Herman, KB; Cheok, J; Ebert, DA; Simpfendorfer, CA; Dulvy, NK. (2020) The thin edge of the wedge: Extremely high extinction risk in wedgefishes and giant guitarfishes.Aquat. Conserv.-Mar. Freshw. Ecosyst. 30: 1337-1361 The thin edge of the wedge: Extremely high extinction risk in wedgefishes and giant guitarfishes
elasmobranchs; historical ecology; IUCN Red List; Red List index; shark-like rays; threatened species; wildlife trade
The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high-value and internationally traded 'white' fins. The objective of this study was to assess the extinction risk of all 10 wedgefishes and six giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarize the latest understanding of their biogeography and habitat, life history, exploitation, use and trade, and population status. Three of the 10 wedgefish species had not been assessed previously for the IUCN Red List. Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction through a combination of traits: limited biological productivity; presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world; and overexploitation in target and by-catch fisheries, driven by the need for animal protein and food security in coastal communities and the trade in meat and high-value fins. Two species with very restricted ranges, the clown wedgefish (Rhynchobatus cooki) of the Malay Archipelago and the false shark ray (Rhynchorhina mauritaniensis) of Mauritania, may be very close to extinction. Only the eyebrow wedgefish (Rhynchobatus palpebratus) is not assessed as Critically Endangered, with it occurring primarily in Australia where fishing pressure is low and some management measures are in place. Australia represents a 'lifeboat' for the three wedgefish and one giant guitarfish species occurring there. To conserve populations and permit recovery, a suite of measures will be required that will need to include species protection, spatial management, by-catch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement. DOI
129. Lawson, JM; Pollom, RA; Gordon, CA; Barker, J; Meyers, EKM; Zidowitz, H; Ellis, JR; Bartoli, A; Morey, G; Fowler, SL; Alvarado, DJ; Fordham, SV; Sharp, R; Hood, AR; Dulvy, NK. (2020) Extinction risk and conservation of critically endangered angel sharks in the Eastern Atlantic and Mediterranean Sea.ICES J. Mar. Sci. 77: 12-29 Extinction risk and conservation of critically endangered angel sharks in the Eastern Atlantic and Mediterranean Sea
biodiversity; conservation planning; EU fisheries policy; fisheries; fisheries management; implementation; IUCN Red List; overfishing; species at risk; trawling
Understanding the details of local and regional extinctions allows for more efficient allocation of conservation activities and resources. This involves identifying where populations persist, where populations may still be present, and where populations may be locally extinct. Three threatened angel sharks occur in the Eastern Atlantic and Mediterranean Sea: Sawback Angelshark (Squatina aculeata), Smoothback Angelshark (Squatina oculata), and Angelshark (Squatina squatina). Population sizes and geographic ranges of these species have been reduced due to overfishing and habitat loss, placing them among the world s most threatened chondrichthyans. We revise distribution maps, review global status, and present a Conservation Strategy to protect and restore these angel shark populations by minimizing fishing mortality, protecting critical habitat, and mitigating human disturbance. Updated distributions reveal that a halving of the geographic extent may have occurred for all three species, with potential declines of 51% for Sawback Angelshark, 48% for Smoothback Angelshark, and 58% for Angelshark. While 20 national and international management measures are now in place for Angelshark, only half of these include the other two species. We encourage further conservation action to adopt and develop this Conservation Strategy to restore angel shark populations to robust levels and safeguard them throughout their range. DOI
128. Mull, CG; Yopak, KE; Dulvy, NK. (2020) Maternal Investment, Ecological Lifestyle, and Brain Evolution in Sharks and Rays.Am. Nat. 195: 1056-1069 Maternal Investment, Ecological Lifestyle, and Brain Evolution in Sharks and Rays
brain evolution; brain organization; oviparity; viviparity; shark; ray
Across vertebrates increased maternal investment (via increased pre- and postnatal provisioning) is associated with larger relative brain size, yet it remains unclear how brain organization is shaped by life history and ecology. Here, we tested whether maternal investment and ecological lifestyle are related to variation in brain size and organization across 100 chondrichthyans. We hypothesized that brain size and organization would vary with the level of maternal investment and habitat depth and complexity. We found that chondrichthyan brain organization varies along four main axes according to (1) absolute brain size, (2) relative diencephalon and mesencephalon size, (3) relative telencephalon and medulla size, and (4) relative cerebellum size. Increased maternal investment is associated with larger relative brain size, while ecological lifestyle is informative for variation between relative telencephalon and medulla size and relative cerebellum size after accounting for the independent effects of reproductive mode. Deepwater chondrichthyans generally provide low levels of yolk-only (lecithotrophic) maternal investment and have relatively small brains, predominantly composed of medulla (a major portion of the hindbrain), whereas matrotrophic chondrichthyans-which provide maternal provisioning beyond the initial yolk sac-found in coastal, reef, or shallow oceanic habitats have relatively large brains, predominantly composed of telencephalon (a major portion of the forebrain). We have demonstrated, for the first time, that both ecological lifestyle and maternal investment are independently associated with brain organization in a lineage with diverse life-history strategies and reproductive modes. DOI PubMed
126. Shiffman, DS; Ajemian, MJ; Carrier, JC; Daly-Engel, TS; Davis, MM; Dulvy, NK; Grubbs, RD; Hinojosa, NA; Imhoff, J; Kolmann, MA; Nash, CS; Paig-Tran, EWM; Peele, EE; Skubel, RA; Wetherbee, BM; Whitenack, LB; Wyffels, JT. (2020) Trends in Chondrichthyan Research: An Analysis of Three Decades of Conference Abstracts.Copeia 108: 122-131 Trends in Chondrichthyan Research: An Analysis of Three Decades of Conference Abstracts
Given the conservation status and ecological, cultural, and commercial importance of chondrichthyan fishes, it is valuable to evaluate the extent to which research attention is spread across taxa and geographic locations and to assess the degree to which scientific research is appropriately addressing the challenges they face. Here we review trends in research effort over three decades (1985-2016) through content analysis of every abstract (n = 2,701) presented at the annual conference of the American Elasmobranch Society (AES), the oldest and largest professional society focused on the scientific study and management of these fishes. The most common research areas of AES abstracts were reproductive biology, movement/telemetry, age and growth, population genetics, and diet/feeding ecology, with different areas of focus for different study species or families. The most commonly studied species were large and charismatic (e.g., White Shark, Carcharodon carcharias), easily accessible to long-term established field research programs (e.g., Lemon Shark, Negaprion brevirostris, and Sandbar Shark, Carcharhinus plumbeus), or easily kept in aquaria for lab-based research (e.g., Bonnethead Shark, Sphyrna tiburo). Nearly 90% of all described chondrichthyan species have never been mentioned in an AES abstract, including some of the most threatened species in the Americas. The proportion of female* first authors has increased over time, though many current female* Society members are graduate students. Nearly half of all research presented at AES occurred in the waters of the United States rather than in the waters of developing nations where there are more threatened species and few resources for research or management. Presentations based on research areas such as paleontology and aquarium-based research have declined in frequency over time, and identified research priorities such as social science and interdisciplinary research are poorly represented. Possible research gaps and future research priorities for the study of chondrichthyan fishes are also discussed. DOI
125. Shiffman, DS; Bittick, SJ; Cashion, MS; Colla, SR; Coristine, LE; Derrick, DH; Gow, EA; Macdonald, CC; O'Ferrall, MM; Orobko, M; Pollom, RA; Provencher, J; Dulvy, NK. (2020) Inaccurate and Biased Global Media Coverage Underlies Public Misunderstanding of Shark Conservation Threats and Solutions.iScience 23 Inaccurate and Biased Global Media Coverage Underlies Public Misunderstanding of Shark Conservation Threats and Solutions
Sharks are a taxon of significant conservation concern and associated public interest. The scientific community largely supports management policies focusing on sustainable fisheries exploitation of sharks, but many concerned members of the public and some environmental advocates believe that sustainable shark fisheries cannot and do not exist and therefore support total bans on all shark fisheries and/or trade in shark products. The belief that sustainable shark fisheries cannot and do not exist persists despite scientific evidence showing that they can and do, and are important to livelihoods. Additionally, many concerned members of the public are only aware of one threat to sharks and are unaware of other threats-or of most available policy solutions. Here we assess whether the popular press plays a role in spreading misinformation and misunderstanding about these issues via the agenda-setting, priming, and cultivation roles of the media, with the goal of better understanding the causes and consequences of public confusion. DOI PubMed
124. Temple, AJ; Stead, SM; Jiddawi, N; Wambiji, N; Dulvy, NK; Barrowclift, E; Berggren, P. (2020) Life-history, exploitation and extinction risk of the data-poor Baraka's whipray (Maculabatis ambigua) in small-scale tropical fisheries.J. Fish Biol.Life-history, exploitation and extinction risk of the data-poor Baraka's whipray (Maculabatis ambigua) in small-scale tropical fisheries
Bland-Altman; elasmobranch; life-history; r(max); Indian Ocean
The Baraka's whipray (Maculabatis ambigua) is a major constituent of small-scale fisheries catch in the south-western Indian Ocean. Despite this, little is known of its life-history or exploitation status. We provide the first estimates of crucial life-history parameters and the maximum intrinsic population growth rater(max), using specimens collected from small-scale fisheries landings in Kenya, Zanzibar and Madagascar (with northern Madagascar representing a range extension for this species). We assess the relative risk of overexploitation by combiningr(max)with estimates of totalZ, fishingF, and naturalMmortality, and an estimate of the exploitation ratioE. The data indicate that Baraka's whipray is a medium-sized, fast-growing, early maturing species, with a relatively long lifespan. This results in a highr(max)relative to many other elasmobranchs, which when combined with estimates ofFsuggests that the species is not at imminent risk of extinction. Yet, estimates of exploitation ratioEindicate likely overfishing for the species, with full recruitment to the fishery being post-maturation and exploitation occurring across a broad range of age and size classes. Thus, Baraka's whipray is unlikely to be biologically sustainable in the face of current fisheries pressures. This paper makes an important contribution to filling the gap in available data and is a step towards developing evidence-based fisheries management for this species. Further, it demonstrates a simple and widely applicable framework for assessment of data-poor elasmobranch exploitation status and extinction risk. DOI PubMed
123. VanderWright, WJ; Bigman, JS; Elcombe, CF; Dulvy, NK. (2020) Gill slits provide a window into the respiratory physiology of sharks.Conserv. Physiol. 8 Gill slits provide a window into the respiratory physiology of sharks
Carcharhinus; Gill Oxygen Limitation Theory; Metabolic Theory of Ecology; Rhizoprionodon terraenovae; shrinking fishes; Sphyrna tiburo
Metabolically important traits, such as gill surface area and metabolic rate, underpin life histories, population dynamics and extinction risk, as they govern the availability of energy for growth, survival and reproduction. Estimating both gill surface area and metabolic rate can be challenging, especially when working with large-bodied, threatened species. Ideally, these traits, and respiratory physiology in general, could be inferred from external morphology using a faster, non-lethal method. Gill slit height is quick to measure on live organisms and is anatomically connected to the gill arch. Here, we relate gill slit height and gill surface area for five Carcharhiniform sharks. We compared both total and parabranchial gill surface area to mean and individual gill slit height in physical specimens. We also compared empirical measurements of relative gill slit height (i.e. in proportion to total length) to those estimated from field guide illustrations to examine the potential of using anatomical drawings to measure gill slit height. We find strong positive relationships between gill slit height and gill surface area at two scales: (i) for total gill surface area and mean gill slit height across species and (ii) for parabranchial gill surface area and individual gill slit height within and across species. We also find that gill slit height is a consistent proportion of the fork length of physical specimens. Consequently, relative gill slit height measured from field guide illustrations proved to be surprisingly comparable to those measured from physical specimens. While the generality of our findings needs to be evaluated across a wider range of taxonomy and ecological lifestyles, they offer the opportunity that we might only need to go to the library and measure field guide illustrations to yield a non-lethal, first- order approximation of the respiratory physiology of sharks. DOI PubMed
122. Walls, RHL; Dulvy, NK. (2020) Eliminating the dark matter of data deficiency by predicting the conservation status of Northeast Atlantic and Mediterranean Sea sharks and rays.Biol. Conserv. 246 Eliminating the dark matter of data deficiency by predicting the conservation status of Northeast Atlantic and Mediterranean Sea sharks and rays
Aichi target; Chondrichthyes; Elasmobranchii; Depth refuge; General Fisheries Commission for the Mediterranean; Red List Index
Sharks and rays are threatened by overfishing, yet we have little idea of the conservation status of the hundreds of Data Deficient species. Here, we developed an ecological trait model to predict the categorical conservation status of 22 Northeast Atlantic and 13 Mediterranean Sea Data Deficient sharks and rays. We first developed an explanatory cumulative link mixed model based on regionally data-sufficient species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (TM) using maximum body size, median depth, and reproductive mode, then predicted the statuses of Data Deficient species. Species exclusive to the Mediterranean were 3.8 times more likely to be threatened than species exclusive to the Northeast Atlantic. Over half of Northeast Atlantic (55%, n = 12 of 22), and two-thirds of Mediterranean (62%, n = 8 of 13) Data Deficient species were predicted to be threatened. When applied to all data-sufficient species, the mean predictive accuracy was 71% and 66% for the Northeast Atlantic and Mediterranean models, respectively. Overall, Northeast Atlantic Data Deficient species are predicted to be 1.4 times more threatened than data-sufficient species proportionally (39% assessed-threatened, n = 38 of 98), whereas threat levels in the Mediterranean Sea are similarly high for both (65% assessed-threatened, n = 39 of 60 data-sufficient). With the growing availability of vertebrate trait databases, trait-based, categorical prediction of conservation status is a cost-effective approach towards incorporating Data Deficient species into unbiased (i) estimates of lineage-wide extinction rates, (ii) protected species lists, and (iii) Red List Indices, thus preventing poorly-known species from reaching extinction unnoticed. DOI
119. Hiddink, JG; Shepperson, J; Bater, R; Goonesekera, D; Dulvy, NK. (2019) Near disappearance of the Angelshark Squatina squatina over half a century of observations.Conserv. Sci. Pract. 1 Near disappearance of the Angelshark Squatina squatina over half a century of observations
Elasmobranchii; fisheries; historical ecology; local ecological knowledge; reconstruction of changes in abundance
Marine extinctions are particularly difficult to detect and almost all have been discovered after the fact. Retrospective analyses are essential to avoid concluding no-extinction when one has occurred. We reconstruct the Angelshark population trajectory in a former hotspot (Wales), using interviews and opportunistic records. After correcting for observation effort and recall bias, we estimate a 70% (1.5%/year) decline in abundance over 46 years. While formerly widespread, Angelshark distribution contracted to a central core of Cardigan Bay. Angelshark declined almost unnoticed in one of the best-monitored and most intensively managed seas in the world. Bycatch may be minimized by limiting netting on shingle reefs in Cardigan Bay. We provide the first quantitative time series to reveal the timing and trajectory of decline of Angelshark in the coastal waters of Wales and uncover historical centers of abundance and remnant populations that provide the first opportunity for the focus of conservation. DOI
118. Horswill, C; Kindsvater, HK; Juan-Jorda, MJ; Dulvy, NK; Mangel, M; Matthiopoulos, J. (2019) Global reconstruction of life-history strategies: A case study using tunas.J. Appl. Ecol. 56: 855-865 Global reconstruction of life-history strategies: A case study using tunas
Bayesian imputation; data limited; demography; fecundity; life-history theory; missing data; principal market tuna; Scombridae
Measuring the demographic parameters of exploited populations is central to predicting their vulnerability and extinction risk. However, current rates of population decline and species loss greatly outpace our ability to empirically monitor all populations that are potentially threatened. The scale of this problem cannot be addressed through additional data collection alone, and therefore it is a common practice to conduct population assessments based on surrogate data collected from similar species. However, this approach introduces biases and imprecisions that are difficult to quantify. Recent developments in hierarchical modelling have enabled missing values to be reconstructed based on the correlations between available life-history data, linking similar species based on phylogeny and environmental conditions. However, these methods cannot resolve life-history variability among populations or species that are closely placed spatially or taxonomically. Here, theoretically motivated constraints that align with life-history theory offer a new avenue for addressing this problem. We describe a Bayesian hierarchical approach that combines fragmented, multispecies and multi-population data with established life-history theory, in order to objectively determine similarity between populations based on trait correlations (life-history trade-offs) obtained from model fitting. We reconstruct 59 unobserved life-history parameters for 23 populations of tuna that sustain some of the world's most valuable fisheries. Testing by cross-validation across different scenarios indicated that life-histories were accurately reconstructed when information was available for other populations of the same species. The reconstruction of several traits was also accurate for species represented by a single population, although credible intervals increased dramatically.Synthesis and applications. The described Bayesian hierarchical method provides access to life-history traits that are difficult to measure directly and reconstructs missing life-history information useful for assessing populations and species that are directly or indirectly affected by human exploitation of natural resources. The method is particularly useful for examining populations that are spatially or taxonomically similar, and the reconstructed life-history strategies described for the principal market tunas have immediate application to the world-wide management of these fisheries. The described Bayesian hierarchical method provides access to life-history traits that are difficult to measure directly and reconstructs missing life-history information useful for assessing populations and species that are directly or indirectly affected by human exploitation of natural resources. The method is particularly useful for examining populations that are spatially or taxonomically similar, and the reconstructed life-history strategies described for the principal market tunas have immediate application to the world-wide management of these fisheries. DOI PubMed
117. Sherley, RB; Winker, H; Rigby, CL; Kyne, PM; Pollom, R; Pacoureau, N; Herman, K; Carlson, JK; Yin, JS; Kindsvater, HK; Dulvy, NK. (2019) Estimating IUCN Red List population reduction: JARA-A decision-support tool applied to pelagic sharks.Conserv. Lett.Estimating IUCN Red List population reduction: JARA-A decision-support tool applied to pelagic sharks
Bayesian state-space model; biodiversity conservation; demography; elasmobranch; extinction risk; population decline; threatened species
The International Union for Conservation of Nature's (IUCN) Red List is the global standard for quantifying extinction risk but assessing population reduction (criterion A) of wide-ranging, long-lived marine taxa remains difficult and controversial. We show how Bayesian state-space models (BSSM), coupled with expert knowledge at IUCN Red List workshops, can combine regional abundance data into indices of global population change. To illustrate our approach, we provide examples of the process to assess four circumglobal sharks with differing temporal and spatial data-deficiency: Blue Shark (Prionace glauca), Shortfin Mako (Isurus oxyrinchus), Dusky Shark (Carcharhinus obscurus), and Great Hammerhead (Sphyrna mokarran). For each species, the BSSM provided global population change estimates over three generation lengths bounded by uncertainty levels in intuitive outputs, enabling informed decisions on the status of each species. Integrating similar analyses into future workshops would help conservation practitioners ensure robust, consistent, and transparent Red List assessments for other long-lived, wide-ranging species. DOI
116. Bigman, JS; Pardo, SA; Prinzing, TS; Dando, M; Wegner, NC; Dulvy, NK. (2018) Ecological lifestyles and the scaling of shark gill surface area.J. Morphol. 279 Ecological lifestyles and the scaling of shark gill surface area
allometry; ecomorphology; gill surface area; metabolism; scaling
Fish gill surface area varies across species and with respect to ecological lifestyles. The majority of previous studies only qualitatively describe gill surface area in relation to ecology and focus primarily on teleosts. Here, we quantitatively examined the relationship of gill surface area with respect to specific ecological lifestyle traits in elasmobranchs, which offer an independent evaluation of observed patterns in teleosts. As gill surface area increases ontogenetically with body mass, examination of how gill surface area varies with ecological lifestyle traits must be assessed in the context of its allometry (scaling). Thus, we examined how the relationship of gill surface area and body mass across 11 shark species from the literature and one species for which we made measurements, the Gray Smoothhound Mustelus californicus, varied with three ecological lifestyle traits: activity level, habitat, and maximum body size. Relative gill surface area (gill surface area at a specified body mass; here we used 5,000g, termed the 'standardized intercept') ranged from 4,724.98 to 35,694.39 cm(2) (mean and standard error: 17,796.65 +/- 2,948.61 cm(2)) and varied across species and the ecological lifestyle traits examined. Specifically, larger-bodied, active, oceanic species had greater relative gill surface area than smaller-bodied, less active, coastal species. In contrast, the rate at which gill surface area scaled with body mass (slope) was generally consistent across species (0.85 +/- 0.02) and did not differ statistically with activity level, habitat, or maximum body size. Our results suggest that ecology may influence relative gill surface area, rather than the rate at which gill surface area scales with body mass. Future comparisons of gill surface area and ecological lifestyle traits using the quantitative techniques applied in this study can provide further insight into patterns dictating the relationship between gill surface area, metabolism, and ecological lifestyle traits. DOI PubMed
115. Jabado, RW; Kyne, PM; Pollom, RA; Ebert, DA; Simpfendorfer, CA; Ralph, GM; Al Dhaheri, SS; Akhilesh, KV; Ali, K; Ali, MH; Al Mamari, TMS; Bineesh, KK; El Hassan, IS; Fernando, D; Grandcourt, EM; Khan, MM; Moore, ABM; Owfi, F; Robinson, DP; Romanov, E; Soares, AL; Spaet, JLY; Tesfamichael, D; Valinassab, T; Dulvy, NK. (2018) Troubled waters: Threats and extinction risk of the sharks, rays and chimaeras of the Arabian Sea and adjacent waters.Fish. Fish. 19 Troubled waters: Threats and extinction risk of the sharks, rays and chimaeras of the Arabian Sea and adjacent waters
chondrichthyans; extinction risk; fisheries; IUCN Red List; population decline; species diversity
The extinction risk of sharks, rays and chimaeras is higher than that for most other vertebrates due to low intrinsic population growth rates of many species and the fishing intensity they face. The Arabian Sea and adjacent waters border some of the most important chondrichthyan fishing and trading nations globally, yet there has been no previous attempt to assess the conservation status of species occurring here. Using IUCN Red List of Threatened Species Categories and Criteria and their guidelines for application at the regional level, we present the first assessment of extinction risk for 153 species of sharks, rays and chimaeras. Results indicate that this region, home to 15% of described chondrichthyans including 30 endemic species, has some of the most threatened chondrichthyan populations in the world. Seventy-eight species (50.9%) were assessed as threatened (Critically Endangered, Endangered or Vulnerable), and 27 species (17.6%) as Near Threatened. Twenty-nine species (19%) were Data Deficient with insufficient information to assess their status. Chondrichthyan populations have significantly declined due to largely uncontrolled and unregulated fisheries combined with habitat degradation. Further, there is limited political will and national and regional capacities to assess, manage, conserve or rebuild stocks. Outside the few deepsea locations that are lightly exploited, the prognosis for the recovery of most species is poor in the near-absence of management. Concerted national and regional management measures are urgently needed to ensure extinctions are avoided, the sustainability of more productive species is secured, and to avoid the continued thinning of the regional food security portfolio. DOI
114. Juan-Jorda, MJ; Murua, H; Arrizabalaga, H; Dulvy, NK; Restrepo, V. (2018) Report card on ecosystem-based fisheries management in tuna regional fisheries management organizations.Fish. Fish. 19 Report card on ecosystem-based fisheries management in tuna regional fisheries management organizations
bycatch; ecosystem impacts; ecosystem-based fisheries management; RFMO; sharks; tunas
International instruments of fisheries governance have set the core principles for the management of highly migratory fishes. We evaluated the progress of tuna Regional Fisheries Management Organizations (tRFMOs) in implementing the ecological component of ecosystem-based fisheries management (EBFM). We first developed a best case tRFMO for EBFM implementation. Second, we developed criteria to evaluate progress in applying EBFM against this best case tRFMO. We assessed progress of the following four ecological components: target species, bycatch species, ecosystem properties and trophic relationships, and habitats. We found that many of the elements necessary for an operational EBFM are already present, yet they have been implemented in an ad hoc way, without a long-term vision and a formalized plan. Overall, tRFMOs have made considerable progress monitoring the impacts of fisheries on target species, moderate progress for bycatch species, and little progress for ecosystem properties and trophic relationships and habitats. The tRFMOs appear to be halfway towards implementing the ecological component of EBFM, yet it is clear that the low-hanging fruit has been plucked and the more difficult, but surmountable, issues remain, notably the sustainable management of bycatch. All tRFMOs share the same challenge of developing a formal mechanism to better integrate ecosystem science and advice into management decisions. We hope to further discussion across the tRFMOs to inform the development of operational EBFM plans. DOI
113. Kindsvater, HK; Dulvy, NK; Horswill, C; Juan-Jorda, MJ; Mangel, M; Matthiopoulos, J. (2018) Overcoming the Data Crisis in Biodiversity Conservation.Trends Ecol. Evol. 33 Overcoming the Data Crisis in Biodiversity Conservation
How can we track population trends when monitoring data are sparse? Population declines can go undetected, despite ongoing threats. For example, only one of every 200 harvested species are monitored. This gapleads to uncertaintyabout the seriousness of declines and hampers effective conservation. Collecting more data is important, but we can also make better use of existing information. Prior knowledge of physiology, life history, and community ecology can be used to inform population models. Additionally, in multispecies models, information can be shared among taxa based on phylogenetic, spatial, or temporal proximity. By exploiting generalities across species that share evolutionary or ecological characteristics within Bayesian hierarchical models, we can fill crucial gaps in the assessment of species' status with unparalleled quantitative rigor. DOI PubMed
112. Leeney, RH; Mana, RR; Dulvy, NK. (2018) Fishers' ecological knowledge of sawfishes in the Sepik and Ramu rivers, northern Papua New Guinea.Endanger. Species Res. 36 Fishers' ecological knowledge of sawfishes in the Sepik and Ramu rivers, northern Papua New Guinea
Pristidae; Extinction risk; Anoxypristis cuspidata; Pristis pristis; Narrow sawfish; Largetooth sawfish; Interview surveys; Bycatch
Papua New Guinea (PNG) is geographically close to northern Australia, a key region tor 4 sawfish species. However, detailed data on sawtish presence in PNG are limited, particularly from the north coast. We conducted a short study to assess whether sawfishes are still present in 2 adjacent rivers - the Sepik and Ramu - in northern PNG. Interviews were conducted with fishers from villages along the Sepik River between Chambri Lake and the river mouth, as well as along the Keram River (a tributary of the Sepik) and the Ramu River. Landings by gillnet fishers at the mouth of the Sepik River were observed. At least 2 species, the narrow sawfish Anoxypristis cuspidata and the largetooth sawfish Pristis pristis, were present at the mouth of the Sepik River and were caught in gillnets used to target sharks and croakers (Sciaenidae). Largetooth sawfish aie still captured by fishers in the freshwater reaches of the Sepik, Ramu, and Keram rivers. The fins of sawfishes and other elasmobranchs provide a source of income, and sawfish meat is eaten locally or sold. The Sepik River and surrounding coastline remains important habitat for sawfishes; however, most interviewees reported a decline in sawfish catches over the course of their lifetimes. These findings corroborate existing evidence suggesting that PNG remains a global stronghold for sawfishes. Immediate collaboration with fishing communities and PNG's fisheries and conservation authorities is needed to ensure that any sawfish catches and habitats are appropriately managed so that populations do not decline further. DOI
111. Pardo, SA; Cooper, AB; Reynolds, JD; Dulvy, NK. (2018) Quantifying the known unknowns: estimating maximum intrinsic rate of population increase in the face of uncertainty.ICES J. Mar. Sci. 75 Quantifying the known unknowns: estimating maximum intrinsic rate of population increase in the face of uncertainty
bycatch; Carcharhinus; Chondrichthyes; demography; Elasmobranchii; reference points; risk assessment
Sensitivity to overfishing is often estimated using simple models that depend upon life history parameters, especially for species lacking detailed biological information. Yet, there has been little exploration of how uncertainty in life history parameters can influence demographic parameter estimates and therefore fisheries management options. We estimate the maximum intrinsic rate of population increase (rmax) for ten coastal carcharhiniform shark populations using an unstructured life history model that explicitly accounts for uncertainty in life history parameters. We evaluate how the two directly estimated parameters, age at maturity amat and annual reproductive output b, most influenced rmax estimates. Uncertainty in age at maturity values was low, but resulted in moderate uncertainty in rmax estimates. The model was sensitive to uncertainty in annual reproductive output for the least fecund species with fewer than 5 female offspring per year, which is not unusual for large elasmobranchs, marine mammals, and seabirds. Managers and policy makers should be careful to restrict mortality on species with very low annual reproductive output< 2 females per year. We recommend elasmobranch biologists to measure frequency distributions of litter sizes (rather than just a range) as well as improving estimates of natural mortality of data-poor elasmobranchs. DOI
110. Stein, RW; Mull, CG; Kuhn, TS; Aschliman, NC; Davidson, LNK; Joy, JB; Smith, GJ; Dulvy, NK; Mooers, AO. (2018) Global priorities for conserving the evolutionary history of sharks, rays and chimaeras.Nat. Ecol. Evol. 2 Global priorities for conserving the evolutionary history of sharks, rays and chimaeras
In an era of accelerated biodiversity loss and limited conservation resources, systematic prioritization of species and places is essential. In terrestrial vertebrates, evolutionary distinctness has been used to identify species and locations that embody the greatest share of evolutionary history. We estimate evolutionary distinctness for a large marine vertebrate radiation on a dated taxon-complete tree for all 1,192 chondrichthyan fishes (sharks, rays and chimaeras) by augmenting a new 610-species molecular phylogeny using taxonomic constraints. Chondrichthyans are by far the most evolutionarily distinct of all major radiations of jawed vertebrates-the average species embodies 26 million years of unique evolutionary history. With this metric, we identify 21 countries with the highest richness, endemism and evolutionary distinctness of threatened species as targets for conservation prioritization. On average, threatened chondrichthyans are more evolutionarily distinct-further motivating improved conservation, fisheries management and trade regulation to avoid significant pruning of the chondrichthyan tree of life. DOI PubMed
109. Anderson, SC; Branch, TA; Cooper, AB; Dulvy, NK. (2017) Black-swan events in animal populations.Proceedings of the National Academy of Sciences of the United States of America 114: 3252-3257 Black-swan events in animal populations
mass mortality; ecological surprises; population dynamics; die-offs; ecological risk
Black swans are improbable events that nonetheless occur-often with profound consequences. Such events drive important transitions in social systems (e.g., banking collapses) and physical systems (e.g., earthquakes), and yet it remains unclear the extent to which ecological population numbers buffer or suffer from such extremes. Here, we estimate the prevalence and direction of black-swan events (heavy-tailed process noise) in 609 animal populations after accounting for population dynamics (productivity, density dependence, and typical stochasticity). We find strong evidence for black-swan events in similar to 4% of populations. These events occur most frequently for birds (7%), mammals (5%), and insects (3%) and are not explained by any life-history covariates but tend to be driven by external perturbations such as climate, severe winters, predators, parasites, or the combined effect of multiple factors. Black-swan events manifest primarily as population die-offs and crashes (86%) rather than unexpected increases, and ignoring heavy-tailed process noise leads to an underestimate in the magnitude of population crashes. We suggest modelers consider heavy-tailed, downward-skewed probability distributions, such as the skewed Student t used here, when making forecasts of population abundance. Our results demonstrate the importance of both modeling heavy-tailed downward events in populations, and developing conservation strategies that are robust to ecological surprises. DOI
107. Blanchard, JL; Watson, RA; Fulton, EA; Cottrell, RS; Nash, KL; Bryndum-Buchholz, A; Buchner, M; Carozza, DA; Cheung, WWL; Elliott, J; Davidson, LNK; Dulvy, NK; Dunne, JP; Eddy, TD; Galbraith, E; Lotze, HK; Maury, O; Muller, C; Tittensor, DP; Jennings, S. (2017) Linked sustainability challenges and trade-offs among fisheries, aquaculture and agriculture.Nature Ecology & Evolution 1: 1240-1249 Linked sustainability challenges and trade-offs among fisheries, aquaculture and agriculture
Fisheries and aquaculture make a crucial contribution to global food security, nutrition and livelihoods. However, the UN Sustainable Development Goals separate marine and terrestrial food production sectors and ecosystems. To sustainably meet increasing global demands for fish, the interlinkages among goals within and across fisheries, aquaculture and agriculture sectors must be recognized and addressed along with their changing nature. Here, we assess and highlight development challenges for fisheries-dependent countries based on analyses of interactions and trade-offs between goals focusing on food, biodiversity and climate change. We demonstrate that some countries are likely to face double jeopardies in both fisheries and agriculture sectors under climate change. The strategies to mitigate these risks will be context-dependent, and will need to directly address the trade-offs among Sustainable Development Goals, such as halting biodiversity loss and reducing poverty. Countries with low adaptive capacity but increasing demand for food require greater support and capacity building to transition towards reconciling trade-offs. Necessary actions are context-dependent and include effective governance, improved management and conservation, maximizing societal and environmental benefits from trade, increased equitability of distribution and innovation in food production, including continued development of low input and low impact aquaculture. DOI
106. Davidson, LNK; Dulvy, NK. (2017) Global marine protected areas to prevent extinctions.Nature Ecology & Evolution 1 Global marine protected areas to prevent extinctions
One goal of global marine protected areas (MPAs) is to ensure they represent a breadth of taxonomic biodiversity. Ensuring representation of species in MPAs, however, would require protecting vast areas of the global oceans and does not explicitly prioritize species of conservation concern. When threatened species are considered, a recent study found that only a small fraction of their geographic ranges are within the global MPA network. Which global marine areas, and what conservation actions beyond MPAs could be prioritized to prevent marine extinctions (Convention on Biological Diversity Aichi Target 12), remains unknown. Here, we use systematic conservation planning approaches to prioritize conservation actions for sharks, rays and chimaeras (class Chondrichthyes). We use chondrichthyans as they have the highest proportion of threatened species of any marine class. We find that expanding the MPA network by 3% in 70 nations would cover half of the geographic range of 99 imperilled endemic chondrichthyans. Our hotspot analysis reveals that just 12 nations harbour more than half (53) of the imperilled endemics. Four of these hotspot nations are within the top ten chondrichthyan fishing nations in the world, but are yet to implement basic chondrichthyan fisheries management. Given their geopolitical realities, conservation action for some countries will require relief and reorganization to enable sustainable fisheries and species protection. DOI
105.Dulvy, NK; Simpfendorfer, CA; Davidson, LNK; Fordham, SV; Brautigam, A; Sant, G; Welch, DJ. (2017) Challenges and Priorities in Shark and Ray Conservation.Curr. Biol. 27: R565-R572 Challenges and Priorities in Shark and Ray Conservation
Sharks, rays, and chimaeras (Class Chondrichthyes; herein 'sharks') are the earliest extant jawed vertebrates and exhibit some of the greatest functional diversity of all vertebrates. Ecologically, they influence energy transfer vertically through trophic levels and sometimes trophic cascades via direct consumption and predation risk. Through movements and migrations, they connect horizontally and temporally across habitats and ecosystems, integrating energy flows at large spatial scales and across time. This connectivity flows from ontogenetic growth in size and spatial movements, which in turn underpins their relatively low reproductive rates compared with other exploited ocean fishes. Sharks are also ecologically and demographically diverse and are taken in a wide variety of fisheries for multiple products (e.g. meat, fins, teeth, and gills). Consequently, a range of fisheries management measures are generally preferable to 'silver bullet' and 'one size fits all' conservation actions. Some species with extremely low annual reproductive output can easily become endangered and hence require strict protections to minimize mortality. Other, more prolific species can withstand fishing over the long term if catches are subject to effective catch limits throughout the species' range. We identify, based on the IUCN Red List status, 64 endangered species in particular need of new or stricter protections and 514 species in need of improvements to fisheries management. We designate priority countries for such actions, recognizing the widely differing fishing pressures and conservation capacity. We hope that this analysis assists efforts to ensure this group of ecologically important and evolutionarily distinct animals can support both ocean ecosystems and human activities in the future. DOI
104. Fernandes, PG; Ralph, GM; Nieto, A; Criado, MG; Vasilakopoulos, P; Maravelias, CD; Cook, RM; Pollom, RA; Kovacic, M; Pollard, D; Farrell, ED; Florin, AB; Polidoro, BA; Lawson, JM; Lorance, P; Uiblein, F; Craig, M; Allen, DJ; Fowler, SL; Walls, RHL; Comeros-Raynal, MT; Harvey, MS; Dureuil, M; Biscoito, M; Pollock, C; Phillips, SRM; Ellis, JR; Papaconstantinou, C; Soldo, A; Keskin, C; Knudsen, SW; de Sola, LG; Serena, F; Collette, BB; Nedreaas, K; Stump, E; Russell, BC; Garcia, S; Afonso, P; Jung, ABJ; Alvarez, H; Delgado, J; Dulvy, NK; Carpenter, KE. (2017) Coherent assessments of Europe's marine fishes show regional divergence and megafauna loss.Nature Ecology & Evolution 1 Coherent assessments of Europe's marine fishes show regional divergence and megafauna loss
Europe has a long tradition of exploiting marine fishes and is promoting marine economic activity through its Blue Growth strategy. This increase in anthropogenic pressure, along with climate change, threatens the biodiversity of fishes and food security. Here, we examine the conservation status of 1,020 species of European marine fishes and identify factors that contribute to their extinction risk. Large fish species (greater than 1.5 m total length) are most at risk; half of these are threatened with extinction, predominantly sharks, rays and sturgeons. This analysis was based on the latest International Union for Conservation of Nature (IUCN) European regional Red List of marine fishes, which was coherent with assessments of the status of fish stocks carried out independently by fisheries management agencies: no species classified by IUCN as threatened were considered sustainable by these agencies. A remarkable geographic divergence in stock status was also evident: in northern Europe, most stocks were not overfished, whereas in the Mediterranean Sea, almost all stocks were overfished. As Europe proceeds with its sustainable Blue Growth agenda, two main issues stand out as needing priority actions in relation to its marine fishes: the conservation of marine fish megafauna and the sustainability of Mediterranean fish stocks. DOI
103. Lawson, JM; Fordham, SV; O'Malley, MP; Davidson, LNK; Walls, RHL; Heupel, MR; Stevens, G; Fernando, D; Budziak, A; Simpfendorfer, CA; Ender, I; Francis, MP; di Sciara, GN; Dulvy, NK. (2017) Sympathy for the devil: a conservation strategy for devil and manta rays.PeerJ 5 Sympathy for the devil: a conservation strategy for devil and manta rays
Elasmobranch; Conservation planning; Convention on the International Trade in Endangered Species (CITES); Convention on the Conservation of Migratory Species of Wild Animals (CMS); Extinction risk International Union for the Conservation of Nature (IUCN); Multilateral Environmental Agreements (MEAs); Tourism; Wildlife trade; Charismatic species
Background. International trade for luxury products, medicines, and tonics poses a threat to both terrestrial and marine wildlife. The demand for and consumption of gill plates (known as Peng Yu Sai, "Fish Gill of Mobulid Ray") from devil and manta rays (subfamily Mobulinae, collectively referred to as mobulids) poses a significant threat to these marine fishes because of their extremely low productivity. The demand for these gill plates has driven an international trade supplied by largely unmonitored and unregulated catches from target, and incidental fisheries around the world. Scientific research, conservation campaigns, and legal protections for devil rays have lagged behind those for manta rays despite similar threats across all mobufids. Methods. To investigate the difference in attention given to devil rays and manta rays, we examined trends in the scientific literature and updated species distribution maps for all mobufids. Using available information on target and incidental fisheries, and gathering information on fishing and trade regulations (at international, national, and territorial levels), we examined how threats and protective measures overlap with species distribution. We then used a species conservation planning approach to develop the Global Devil and Manta Ray Conservation Strategy, specifying a vision, goals, objectives, and actions to advance the knowledge and protection of both devil and manta rays. Results and Discussion. Our literature review revealed that there had been nearly 2.5-times more "manta"-titled publications, than "mobula" or "devil ray"-titled publications over the Past 4.5 years (January 2012 June 2016). The majority of these recent publications were reports on occurrence of mobulid species. These publications contributed to updated Area of Occupancy and Extent of Occurrence maps which showed expanded distributions for most mobulid species and overlap between the two genera. While several international protections have recently expanded to include all mobulids, there remains a greater number of national, state, and territory-level protections for manta rays compared to devil rays. We hypothesize that there are fewer scientific publications and regulatory protections for devil rays due primarily to perceptions of charisma that favour manta rays. We suggest that the well-established species conservation framework used here offers an objective solution to close this gap. To advance the goals of the conservation strategy we highlight opportunities for parity in protection and suggest solutions to help reduce target and by catch fisheries. DOI
101. Arthington, AH; Dulvy, NK; Gladstone, W; Winfield, IJ. (2016) Fish conservation in freshwater and marine realms: status, threats and management.Aquatic Conservation-Marine and Freshwater Ecosystems 26: 838-857 Fish conservation in freshwater and marine realms: status, threats and management
extinction risk; threats; correlates of risk; conservation reserves; restoration; recovery plans; fisheries management; climate change
1. Despite the disparities in size and volume of marine and freshwater realms, a strikingly similar number of species is found in each - with 15 150 Actinopterygian fishes in fresh water and 14 740 in the marine realm. Their ecological and societal values are widely recognized yet many marine and freshwater fishes increasingly risk local, regional or global extinction. 2. The prevailing threats in aquatic systems are habitat loss and degradation, invasive species, pollution, over-exploitation and climate change. Unpredictable synergies with climate change greatly complicate the impacts of other stressors that threaten many marine and freshwater fishes. 3. Isolated and fragmented habitats typically present the most challenging environments for small, specialized freshwater and marine fishes, whereas overfishing is by far the greatest threat to larger marine and freshwater species. Species that migrate within or between freshwater and marine realms may face high catchability in predictable migration bottlenecks, and degradation of breeding habitat, feeding habitat or the intervening migration corridors. 4. Conservation reserves are vital to protect species-rich habitats, important radiations, and threatened endemic species. Integration of processes that connect terrestrial, freshwater and marine protected areas promises more effective conservation outcomes than disconnected reserves. Diadromous species in particular require more attention in aquatic restoration and conservation planning across disparate government agencies. 5. Human activities and stressors that increasingly threaten freshwater and marine fishes must be curbed to avoid a wave of extinctions. Freshwater recovery programmes range from plans for individual species to recovery of entire basin faunas. Reducing risks to threatened marine species in coastal habitats also requires conservation actions at multiple scales. Most of the world's larger economically important fisheries are relatively well-monitored and well-managed but there are urgent needs to curb fishing mortality and minimize catch of the most endangered species in both realms. Copyright (C) 2016 John Wiley & Sons, Ltd. DOI
100. Collen, B; Dulvy, NK; Gaston, KJ; Gardenfors, U; Keith, DA; Punt, AE; Regan, HM; Bohm, M; Hedges, S; Seddon, M; Butchart, SHM; Hilton-Taylor, C; Hoffmann, M; Bachman, SP; Akcakaya, HR. (2016) Clarifying misconceptions of extinction risk assessment with the IUCN Red List.Biology Letters 12 Clarifying misconceptions of extinction risk assessment with the IUCN Red List
climate change; geographical range; population decline; rarity; spatial autocorrelation; uncertainty
The identification of species at risk of extinction is a central goal of conservation. As the use of data compiled for IUCN Red List assessments expands, a number of misconceptions regarding the purpose, application and use of the IUCN Red List categories and criteria have arisen. We outline five such classes of misconception; the most consequential drive proposals for adapted versions of the criteria, rendering assessments among species incomparable. A key challenge for the future will be to recognize the point where understanding has developed so markedly that it is time for the next generation of the Red List criteria. We do not believe we are there yet but, recognizing the need for scrutiny and continued development of Red Listing, conclude by suggesting areas where additional research could be valuable in improving the understanding of extinction risk among species. DOI
99. Croll, DA; Dewar, H; Dulvy, NK; Fernando, D; Francis, MP; Galvan-Magana, F; Hall, M; Heinrichs, S; Marshall, A; Mccauley, D; Newton, KM; Notarbartolo-Di-Sciara, G; O'Malley, M; O'Sullivan, J; Poortvliet, M; Roman, M; Stevens, G; Tershy, BR; White, WT. (2016) Vulnerabilities and fisheries impacts: the uncertain future of manta and devil rays.Aquatic Conservation-Marine and Freshwater Ecosystems 26: 562-575 Vulnerabilities and fisheries impacts: the uncertain future of manta and devil rays
coastal; ocean; conservation evaluation; endangered species; fish; fishing
1. Manta and devil rays of the subfamily Mobulinae (mobulids) are rarely studied, large, pelagic elasmobranchs, with all eight of well-evaluated species listed on the IUCN Red List as threatened or near threatened. 2. Mobulids have life history characteristics (matrotrophic reproduction, extremely low fecundity, and delayed age of first reproduction) that make them exceptionally susceptible to overexploitation. 3. Targeted and bycatch mortality from fisheries is a globally important and increasing threat, and targeted fisheries are incentivized by the high value of the global trade in mobulid gill plates. 4. Fisheries bycatch of mobulids is substantial in tuna purse seine fisheries. 5. Thirteen fisheries in 12 countries specifically targeting mobulids, and 30 fisheries in 23 countries with mobulid bycatch were identified. 6. Aside from a few recently enacted national restrictions on capture, there is no comprehensive monitoring, assessment or control of mobulid fisheries or bycatch. Recent listing through the Convention on the International Trade in Endangered Species (CITES) may benefit mobulids of the genus Manta (manta rays), but none of the mobulids in the genus Mobula (devil rays) are protected. 7. The relative economic costs of catch mitigation are minimal, particularly compared with a broad range of other, more complicated, marine conservation issues. Copyright (C) 2015 John Wiley & Sons, Ltd. DOI
98. Davidson, LNK; Krawchuk, MA; Dulvy, NK. (2016) Why have global shark and ray landings declined: improved management or overfishing?Fish and Fisheries 17: 438-458 Why have global shark and ray landings declined: improved management or overfishing?
Conservation; Convention on International Trade in Endangered Species; elasmobranch; fin trade; fishing mortality; National Plans of Action
Global chondrichthyan (shark, ray, skate and chimaera) landings, reported to the United Nations Food and Agriculture Organization (FAO), peaked in 2003 and in the decade since have declined by almost 20%. In the FAO's 2012 'State of the World's Fisheries and Aquaculture' report, the authors 'hoped' the reductions in landings were partially due to management implementation rather than population decline. Here, we tested their hypothesis. Post-peak chondrichthyan landings trajectories from 126 countries were modelled against seven indirect and direct fishing pressure measures and eleven measures of fisheries management performance, while accounting for ecosystem attributes. We found the recent improvement in international or national fisheries management was not yet strong enough to account for the recent decline in chondrichthyan landings. Instead, the landings declines were more closely related to fishing pressure and ecosystem attribute measures. Countries with the greatest declines had high human coastal population sizes or high shark and ray meat exports such as Pakistan, Sri Lanka and Thailand. While important progress had been made, country-level fisheries management measures did not yet have the strength or coverage to halt overfishing and avert population declines of chondrichthyans. Increased implementation of legally binding operational fisheries management and species-specific reporting is urgently required to avoid declines and ensure fisheries sustainability and food security. DOI
97.Dulvy, NK; Davidson, LNK; Kyne, PM; Simpfendorfer, CA; Harrison, LR; Carlson, JK; Fordham, SV. (2016) Ghosts of the coast: global extinction risk and conservation of sawfishes.Aquatic Conservation-Marine and Freshwater Ecosystems 26: 134-153 Ghosts of the coast: global extinction risk and conservation of sawfishes
estuary; functional redundancy; habitat degradation and loss; mangrove; range contraction
1. Sawfish are arguably the world's most imperilled marine fishes. All five species are classified as highly threatened with extinction: three are Critically Endangered (smalltooth sawfish Pristis pectinata, largetooth sawfish Pristis pristis, and green sawfish Pristis zijsron); two are Endangered (narrow sawfish Anoxypristis cuspidata, and dwarf sawfish Pristis clavata). 2. Sawfishes are threatened primarily due to a combination of their low intrinsic rates of population increase, high catchability in fisheries, and high value. Sawfishes are among the world's largest marine fishes, and they are caught by a wide range of fishing gears owing to their tooth-studded rostra being easily entangled. Sawfish fins are some of the most valuable for shark fin soup, and their rostra have long been traded as curios. In addition, they inhabit shallow coastal waters, estuaries, and rivers of the tropics and subtropics, down to a maximum depth rarely exceeding 100 m and are associated with threatened mangrove and seagrass habitats. 3. Historically, sawfishes were distributed in the coastal waters of 90 countries and territories. Over the past century, their geographic distribution has been greatly diminished. For example, the smalltooth sawfish is now found in <20% of its former range. Globally, sawfishes are now entirely absent from 20 countries; 43 countries have lost at least one species. 4. Sawfishes are legally protected, to some degree, in 16 of the 90 range states. These safeguards encompass, on average, 81% of their Extant distribution; however, the quality and breadth of protection varies dramatically across countries and species. Smalltooth sawfish currently has the least amount of such coverage of only half (49%) of Extant distribution. 5. he global conservation strategy specifies actions to protect sawfish and their habitats. Such actions are urgently warranted to avoid global extinction and to restore robust populations for the benefit of coastal ecosystem function and biodiversity. (c) 2014 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd. DOI
96. Kindsvater, HK; Mangel, M; Reynolds, JD; Dulvy, NK. (2016) Ten principles from evolutionary ecology essential for effective marine conservation.Ecology and Evolution 6: 2125-2138 Ten principles from evolutionary ecology essential for effective marine conservation
Conservation; demography; extinction risk; fish; life-history theory; management; reference points; sustainability
Sustainably managing marine species is crucial for the future health of the human population. Yet there are diverse perspectives concerning which species can be exploited sustainably, and how best to do so. Motivated by recent debates in the published literature over marine conservation challenges, we review ten principles connecting life-history traits, population growth rate, and density-dependent population regulation. We introduce a framework for categorizing life histories, POSE (Precocial-Opportunistic-Survivor-Episodic), which illustrates how a species' life-history traits determine a population's compensatory capacity. We show why considering the evolutionary context that has shaped life histories is crucial to sustainable management. We then review recent work that connects our framework to specific opportunities where the life-history traits of marine species can be used to improve current conservation practices. DOI
95. McClenachan, L; Cooper, AB; Dulvy, NK. (2016) Rethinking Trade-Driven Extinction Risk in Marine and Terrestrial Megafauna.Current Biology 26: 1640-1646 Rethinking Trade-Driven Extinction Risk in Marine and Terrestrial Megafauna
Large animals hunted for the high value of their parts (e.g., elephant ivory and shark fins) are at risk of extinction due to both intensive international trade pressure and intrinsic biological sensitivity. However, the relative role of trade, particularly in non-perishable products, and biological factors in driving extinction risk is not well understood [1-4]. Here we identify a taxonomically diverse group of >100 marine and terrestrial megafauna targeted for international luxury markets; estimate their value across three points of sale; test relationships among extinction risk, high value, and body size; and quantify the effects of two mitigating factors: poaching fines and geographic range size. We find that body size is the principal driver of risk for lower value species, but that this biological pattern is eliminated above a value threshold, meaning that the most valuable species face a high extinction risk regardless of size. For example, once mean product values exceed US$12,557 kg(-1), body size no longer drives risk. Total value scales with size for marine animals more strongly than for terrestrial animals, incentivizing the hunting of large marine individuals and species. Poaching fines currently have little effect on extinction risk; fines would need to be increased 10- to 100-fold to be effective. Large geographic ranges reduce risk for terrestrial, but not marine, species, whose ranges are ten times greater. Our results underscore both the evolutionary and ecosystem consequences of targeting large marine animals and the need to geographically scale up and prioritize conservation of high-value marine species to avoid extinction. DOI
94. Pardo, SA; Kindsvater, HK; Cuevas-Zimbron, E; Sosa-Nishizaki, O; Perez-Jimenez, JC; Dulvy, NK. (2016) Growth, productivity, and relative extinction risk of a data-sparse devil ray.Scientific Reports 6 Growth, productivity, and relative extinction risk of a data-sparse devil ray
Devil rays (Mobula spp.) face intensifying fishing pressure to meet the ongoing international demand for gill plates. The paucity of information on growth, mortality, and fishing effort for devil rays make quantifying population growth rates and extinction risk challenging. Furthermore, unlike manta rays (Manta spp.), devil rays have not been listed on CITES. Here, we use a published size-at-age dataset for the Spinetail Devil Ray (Mobula japanica), to estimate somatic growth rates, age at maturity, maximum age, and natural and fishing mortality. We then estimate a plausible distribution of the maximum intrinsic population growth rate (r(max)) and compare it to 95 other chondrichthyans. We find evidence that larger devil ray species have low somatic growth rate, low annual reproductive output, and low maximum population growth rates, suggesting they have low productivity. Fishing rates of a small-scale artisanal Mexican fishery were comparable to our estimate of r(max), and therefore probably unsustainable. Devil ray r(max) is very similar to that of manta rays, indicating devil rays can potentially be driven to local extinction at low levels of fishing mortality and that a similar degree of protection for both groups is warranted. DOI
93. Pardo, SA; Kindsvater, HK; Reynolds, JD; Dulvy, NK. (2016) Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity.Canadian Journal of Fisheries and Aquatic Sciences 73: 1159-1163 Maximum intrinsic rate of population increase in sharks, rays, and chimaeras: the importance of survival to maturity
The maximum intrinsic rate of population increase (r(max)) is a commonly estimated demographic parameter used in assessments of extinction risk. In teleosts, r(max) can be calculated using an estimate of spawners per spawner, but for chondrichthyans, most studies have used annual reproductive output (b) instead. This is problematic as it effectively assumes all juveniles survive to maturity. Here, we propose an updated r(max) equation that uses a simple mortality estimator that also accounts for survival to maturity: the reciprocal of average life-span. For 94 chondrichthyans, we now estimate that r(max) values are on average 10% lower than previously published. Our updated r(max) estimates are lower than previously published for species that mature later relative to maximum age and those with high annual fecundity. The most extreme discrepancies in r(max) values occur in species with low age at maturity and low annual reproductive output. Our results indicate that chondrichthyans that mature relatively later in life, and to a lesser extent those that are highly fecund, are less resilient to fishing than previously thought. DOI
92. Trebilcou, R; Dulvy, NK; Anderson, SC; Salomon, AK. (2016) The paradox of inverted biomass pyramids in kelp forest fish communities.Proceedings of the Royal Society B-Biological Sciences 283 The paradox of inverted biomass pyramids in kelp forest fish communities
ecosystem baseline; fractionation; habitat complexity; species interaction; size spectra; stable isotope analysis
Theory predicts that bottom-heavy biomass pyramids or 'stacks' should predominate in real-world communities if trophic-level increases with body size (mean predator-to-prey mass ratio (PPMR) more than 1). However, recent research suggests that inverted biomass pyramids (IBPs) characterize relatively pristine reef fish communities. Here, we estimated the slope of a kelp forest fish community biomass spectrum from underwater visual surveys. The observed biomass spectrum slope is strongly positive, reflecting an IBP. This is incongruous with theory because this steep positive slope would only be expected if trophic position decreased with increasing body size (consumer-to-resource mass ratio, less than 1). We then used delta N-15 signatures of fish muscle tissue to quantify the relationship between trophic position and body size and instead detected strong evidence for the opposite, with PPMR 1650 (50% credible interval 280-12 000). The natural history of kelp forest reef fishes suggests that this paradox could arise from energetic subsidies in the form of movement of mobile consumers across habitats, and from seasonally pulsed production inputs at small body sizes. There were four to five times more biomass at large body sizes (1-2 kg) than would be expected in a closed steady-state community providing a measure of the magnitude of subsidies. DOI
91. Anderson, SC; Moore, JW; McClure, MM; Dulvy, NK; Cooper, AB. (2015) Portfolio conservation of metapopulations under climate change.Ecological Applications 25: 559-572 Portfolio conservation of metapopulations under climate change
biocomplexity; diversity-stability ecosystem-based management; Oncorhynchus spp; Pacific salmon; portfolio effect; prioritization; range contraction; response diversity; risk assessment; stochastic simulation
Climate change is likely to lead to increasing population variability and extinction risk. Theoretically, greater population diversity should buffer against rising climate variability, and this theory is often invoked as a reason for greater conservation. However, this has rarely been quantified. Here we show how a portfolio approach to managing population diversity can inform metapopulation conservation priorities in a changing world. We develop a salmon metapopulation model in which productivity is driven by spatially distributed thermal tolerance and patterns of short- and long-term climate change. We then implement spatial conservation scenarios that control population carrying capacities and evaluate the metapopulation portfolios as a financial manager might: along axes of conservation risk and return. We show that preserving a diversity of thermal tolerances minimizes risk, given environmental stochasticity, and ensures persistence, given long-term environmental change. When the thermal tolerances of populations are unknown, doubling the number of populations conserved may nearly halve expected metapopulation variability. However, this reduction in variability can come at the expense of long-term persistence if climate change increasingly restricts available habitat, forcing ecological managers to balance society's desire for short-term stability and long-term viability. Our findings suggest the importance of conserving the processes that promote thermal-tolerance diversity, such as genetic diversity, habitat heterogeneity, and natural disturbance regimes, and demonstrate that diverse natural portfolios may be critical for metapopulation conservation in the face of increasing climate variability and change. DOI
90. d'Eon-Eggertson, F; Dulvy, NK; Peterman, RM. (2015) Reliable Identification of Declining Populations in an Uncertain World.Conservation Letters 8: 86-96 Reliable Identification of Declining Populations in an Uncertain World
Decline indicators; error rates; IUCN; Monte Carlo simulation; extinction-risk assessment; process variation; observation error
Assessments of extinction risk based on population declines are widely used, yet scientists have little quantitative understanding of their reliability. Incorrectly classifying whether a population is declining or not can lead to inappropriate conservation actions or management measures, with potentially profound societal costs. Here we evaluate key causes of misclassification of decline status and assess the reliability of 20 decline metrics using a stochastic model to simulate time series of population abundance of sockeye salmon (Oncorhynchus nerka). We show that between-year variability in population productivity (process variation) and, to a lesser extent, variability in abundance estimates (observation error) are important causes of unreliable identification of population status. We found that using all available data, rather than just the most recent three generations, consistently improved the reliability of risk assessments. The approach outlined here can improve understanding of the reliability of risk assessments, thereby reducing concerns that may impede their use for exploited taxa such as marine fishes. DOI
89.Dulvy, NK; Kindsvater, HK. (2015) Recovering the potential of coral reefs.Nature 520: 304-305 Recovering the potential of coral reefs
An analysis of fish declines in coral reefs shows that simple fishing limits and implementation of marine protected areas can be enough to support recovery of coral ecosystem resilience. PubMed
87. Juan-Jorda, MJ; Mosqueira, I; Freire, J; Dulvy, NK. (2015) Population declines of tuna and relatives depend on their speed of life.Proceedings of the Royal Society B-Biological Sciences 282 Population declines of tuna and relatives depend on their speed of life
vulnerability; declines; life histories; fishes; fishing mortality; scombrids
Larger-bodied species in a wide range of taxonomic groups including mammals, fishes and birds tend to decline more steeply and are at greater risk of extinction. Yet, the diversity in life histories is governed not only by body size, but also by time-related traits. A key question is whether this size-dependency of vulnerability also holds, not just locally, but globally across a wider range of environments. We test the relative importance of size-and time-related life-history traits and fishing mortality in determining population declines and current exploitation status in tunas and their relatives. We use high-quality datasets of half a century of population trajectories combined with population-level fishing mortalities and life-history traits. Time-related traits (e.g. growth rate), rather than size-related traits (e.g. maximum size), better explain the extent and rate of declines and current exploitation status across tuna assemblages, after controlling for fishing mortality. Consequently, there is strong geographical patterning in population declines, such that populations with slower life histories (found at higher cooler latitudes) have declined most and more steeply and have a higher probability of being overfished than populations with faster life histories (found at tropical latitudes). Hence, the strong, temperature-driven, latitudinal gradients in life-history traits may underlie the global patterning of population declines, fisheries collapses and local extinctions. DOI
86. Keith, D; Akcakaya, HR; Butchart, SHM; Collen, B; Dulvy, NK; Holmes, EE; Hutchings, JA; Keinath, D; Schwartz, MK; Shelton, AO; Waples, RS. (2015) Temporal correlations in population trends: Conservation implications from time-series analysis of diverse animal taxa.Biological Conservation 192: 247-257 Temporal correlations in population trends: Conservation implications from time-series analysis of diverse animal taxa
Population growth rate; Population trend; Endangered species; Time series; Vertebrates
Population trends play a large role in species risk assessments and conservation planning, and species are often considered threatened if their recent rate of decline meets certain thresholds, regardless how large the population is. But how reliable an indicator of extinction risk is a single estimate of population trend? Given the integral role this decline-based approach has played in setting conservation priorities, it is surprising that it has undergone little empirical scrutiny. We compile an extensive global dataset of time series of abundance data for over 1300 vertebrate populations to provide the first major test of the predictability of population growth rates in nature. We divided each time series into assessment and response periods and examined the correlation between growth rates in the two time periods. In birds, population declines tended to be followed by further declines, but mammals, salmon, and other bony fishes showed the opposite pattern: past declines were associated with subsequent population increases, and vice versa. Furthermore, in these taxa subsequent growth rates were higher when initial declines were more severe. These patterns agreed with data simulated under a null model for a dynamically stable population experiencing density dependence. However, this type of result could also occur if conservation actions positively affected the population following initial declines a scenario that our data were too limited to rigorously evaluate. This ambiguity emphasizes the importance of understanding the underlying causes of population trajectories in drawing inferences about rates of decline in abundance. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). DOI
85. Shelton, AO; Hutchings, JA; Waples, RS; Keith, DM; Akcakaya, HR; Dulvy, NK. (2015) Maternal age effects on Atlantic cod recruitment and implications for future population trajectories.ICES Journal of Marine Science 72: 1769-1778 Maternal age effects on Atlantic cod recruitment and implications for future population trajectories
age-structure; age truncation; maternal effects; recruitment; Ricker; productivity
Exploited fish populations frequently exhibit truncated age-structure. To address a basic question in fisheries science and conservation biology-how does age truncation affect population dynamics and productivity?-we explored the effect of age-structure on recruitment dynamics of ten stocks of Atlantic cod (Gadus morhua). Based on six alternative stock-recruitment relationships, we compared models that included and excluded maternal age-structure effects on recruitment. In all ten stocks, a recruitment model that included a maternal age-dependent effect was preferred over the standard Ricker model and in seven of the ten stocks, the preferred statistical model included a positive effect of either maternal age or mass on recruitment. Simulations comparing standard and maternal age dependent recruitment two decades into the future suggest that the inclusion of maternal age in recruitment models has little effect on projected biomasses. However, this similarity in biomass trajectory masked an increased sensitivity of populations with maternal age-dependent recruitment to stock age-structure. In particular, simulations with maternal age-dependent recruitment responded strongly to changes in fishing mortality on the oldest age classes, while simulations using standard recruitment models did not. Populations with maternal age-dependent recruitment can exhibit increased biomass catch even if fishing mortality on older individuals was reduced. Overall, simulations suggested that the influence of maternal age on population dynamics are more nuanced than suggested by previous research and indicate that careful consideration of the effects of age-structure on populations may lead to substantially different fisheries management reference points-particularly with respect to age-specific fishing mortality-than classical models. While these results suggest a link between maternal age and population productivity, future research requires the incorporation of biologically reasonable and empirically defensible mechanisms to clarify the effect of age on population dynamics. DOI
84. Tamburello, N; Côté, IM; Dulvy, NK. (2015) Energy and the Scaling of Animal Space Use.American Naturalist 186: 196-211 Energy and the Scaling of Animal Space Use
allometry; home range; metabolic theory; prey handling; prey size; spatial ecology
Daily animal movements are usually limited to a discrete home range area that scales allometrically with body size, suggesting that home-range size is shaped by metabolic rates and energy availability across species. However, there is little understanding of the relative importance of the various mechanisms proposed to influence home-range scaling (e.g., differences in realm productivity, thermoregulation, locomotion strategy, dimensionality, trophic guild, and prey size) and whether these extend beyond the commonly studied birds and mammals. We derive new home-range scaling relationships for fishes and reptiles and use a model-selection approach to evaluate the generality of home-range scaling mechanisms across 569 vertebrate species. We find no evidence that home-range allometry varies consistently between aquatic and terrestrial realms or thermoregulation strategies, but we find that locomotion strategy, foraging dimension, trophic guild, and prey size together explain 80% of the variation in home-range size across vertebrates when controlling for phylogeny and tracking method. Within carnivores, smaller relative prey size among gape-limited fishes contributes to shallower scaling relative to other predators. Our study reveals how simple morphological traits and prey-handling ability can profoundly influence individual space use, which underpins broader-scale patterns in the spatial ecology of vertebrates. DOI
83. Trebilco, R; Dulvy, NK; Stewart, H; Salomon, AK. (2015) The role of habitat complexity in shaping the size structure of a temperate reef fish community.Marine Ecology Progress Series 532: 197-211 The role of habitat complexity in shaping the size structure of a temperate reef fish community
Biomass size spectra; Community ecology; Coral reef; Ecosystem baseline; Energy flow; Foundation species
Understanding how habitat complexity shapes fish communities is necessary to predict the consequences of future habitat change. On temperate rocky reefs, the presence and characteristics of canopy-forming kelps and the architectural complexity, or rugosity, of the underlying rocky substratum are foundational elements of habitat complexity. However, it is not yet clear how these factors shape the size structure of rocky-reef-associated fish communities. Here, we use biomass spectrum models to evaluate how fish community size structure in high-latitude rocky-reef kelp forests is shaped by substratum rugosity and the degree of closure and density of the kelp canopy. We found that the presence of a closed kelp canopy was associated with an average 75% increase in overall fish biomass compared to open-canopy reefs. Furthermore, on the highest-rugosity reefs, the biomass of small fishes (32-64 g) was 800% higher than on the lowest-rugosity reefs, while large fish (1-2 kg) biomass was 60% lower. Consequently, biomass was more evenly distributed across body-size classes on high-rugosity reefs. By decomposing the biomass spectrum into total biomass and mean individual body mass, we found that higher kelp stipe densities also tended to be associated with larger fishes, but this effect was outweighed by the tendency for more small-bodied fishes with increasing rugosity. This study demonstrates how size-based analyses can give new insights into the ecology of temperate reef communities, and may be useful for tracking changes in kelp-associated assemblages in the coming decades with the maturation of marine protected areas, the recovery of sea otter populations, and changing climate. DOI
82. Bates, AE; Pecl, GT; Frusher, S; Hobday, AJ; Wernberg, T; Smale, DA; Sunday, JM; Hill, NA; Dulvy, NK; Colwell, RK; Holbrook, NJ; Fulton, EA; Slawinski, D; Feng, M; Edgar, GJ; Radford, BT; Thompson, PA; Watson, RA. (2014) Defining and observing stages of climate-mediated range shifts in marine systems.Global Environmental Change-Human and Policy Dimensions 26: 27-38 Defining and observing stages of climate-mediated range shifts in marine systems
Species redistribution; Attribution; Prediction; Biogeography; Warming; Abundance-occupancy relationship
Climate change is transforming the structure of biological communities through the geographic extension and contraction of species' ranges. Range edges are naturally dynamic, and shifts in the location of range edges occur at different rates and are driven by different mechanisms. This leads to challenges when seeking to generalize responses among taxa and across systems. We focus on warming-related range shifts in marine systems to describe extensions and contractions as stages. Range extensions occur as a sequence of (1) arrival, (2) population increase, and (3) persistence. By contrast, range contractions occur progressively as (1) performance decline, (2) population decrease and (3) local extinction. This stage-based framework can be broadly applied to geographic shifts in any species, life-history stage, or population subset. Ideally the probability of transitioning through progressive range shift stages could be estimated from empirical understanding of the various factors influencing range shift rates. Nevertheless, abundance and occupancy data at the spatial resolution required to quantify range shifts are often unavailable and we suggest the pragmatic solution of considering observations of range shifts within a confidence framework incorporating the type, amount and quality of data. We use case studies to illustrate how diverse evidence sources can be used to stage range extensions and contractions and assign confidence that an observed range shift stage has been reached. We then evaluate the utility of trait-based risk (invasion) and vulnerability (extinction) frameworks for application in a range shift context and find inadequacies, indicating an important area for development. We further consider factors that influence rates of extension and contraction of range edges in marine habitats. Finally, we suggest approaches required to increase our capacity to observe and predict geographic range shifts under climate change. (C) 2014 Elsevier Ltd. All rights reserved. DOI
81. Connors, BM; Cooper, AB; Peterman, RM; Dulvy, NK. (2014) The false classification of extinction risk in noisy environments.Proc. R. Soc. B-Biol. Sci. 281 The false classification of extinction risk in noisy environments
false-positives; false-negatives; autocorrelation; process variation; observation error; global population dynamics database
Abundance trends are the basis for many classifications of threat and recovery status, but they can be a challenge to interpret because of observation error, stochastic variation in abundance (process noise) and temporal autocorrelation in that process noise. To measure the frequency of incorrectly detecting a decline (false-positive or false alarm) and failing to detect a true decline (false-negative), we simulated stable and declining abundance time series across several magnitudes of observation error and autocorrelated process noise. We then empirically estimated the magnitude of observation error and autocorrelated process noise across a broad range of taxa and mapped these estimates onto the simulated parameter space. Based on the taxa we examined, at low classification thresholds (30% decline in abundance) and short observation windows (10 years), false alarms would be expected to occur, on average, about 40% of the time assuming density-independent dynamics, whereas false-negatives would be expected to occur about 60% of the time. However, false alarms and failures to detect true declines were reduced at higher classification thresholds (50% or 80% declines), longer observation windows (20, 40, 60 years), and assuming density-dependent dynamics. The lowest false-positive and false-negative rates are likely to occur for large-bodied, long-lived animal species. DOI PubMed
80.Dulvy, NK; Fowler, SL; Musick, JA; Cavanagh, RD; Kyne, PM; Harrison, LR; Carlson, JK; Davidson, LNK; Fordham, SV; Francis, MP; Pollock, CM; Simpfendorfer, CA; Burgess, GH; Carpenter, KE; Compagno, LJV; Ebert, DA; Gibson, C; Heupel, MR; Livingstone, SR; Sanciangco, JC; Stevens, JD; Valenti, S; White, WT. (2014) Extinction risk and conservation of the world's sharks and rays.Elife 3 Extinction risk and conservation of the world's sharks and rays
The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes-sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world's ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery. DOI
79.Dulvy, NK; Pardo, SA; Simpfendorfer, CA; Carlson, JK. (2014) Diagnosing the dangerous demography of manta rays using life history theory.PeerJ 2 Diagnosing the dangerous demography of manta rays using life history theory
CITES; Data-poor fisheries; Life history invariant; Wildlife trade; Euler-Lotka; Population growth rate; Accounting for uncertainty; Von Bertalanffy growth function; Ocean ivory; Chinese medicine
Background. The directed harvest and global trade in the gill plates of mantas, and devil rays, has led to increased fishing pressure and steep population declines in some locations. The slow life history, particularly of the manta rays, is cited as a key reason why such species have little capacity to withstand directed fisheries. Here, we place their life history and demography within the context of other sharks and rays. Methods. Despite the limited availability of data, we use life history theory and comparative analysis to estimate the intrinsic risk of extinction (as indexed by the maximum intrinsic rate of population increase r(max)) for a typical generic manta ray using a variant of the classic Euler-Lotka demographic model. This model requires only three traits to calculate the maximum intrinsic population growth rate r(max): von Bertalanffy growth rate, annual pup production and age at maturity. To account for the uncertainty in life history parameters, we created plausible parameter ranges and propagate these uncertainties through the model to calculate a distribution of the plausible range of rmax values. Results. The maximum population growth rate rmax of manta ray is most sensitive to the length of the reproductive cycle, and the median rmax of 0.116 year(-1) 95th percentile [0.089-0.139] is one of the lowest known of the 106 sharks and rays for which we have comparable demographic information. Discussion. In common with other unprotected, unmanaged, high-value largebodied sharks and rays the combination of very low population growth rates of manta rays, combined with the high value of their gill rakers and the international nature of trade, is highly likely to lead to rapid depletion and potential local extinction unless a rapid conservation management response occurs worldwide. Furthermore, we show that it is possible to derive important insights into the demography extinction risk of data-poor species using well-established life history theory. DOI PubMed
78. Green, SJ; Dulvy, NK; Brooks, AML; Akins, JL; Cooper, AB; Miller, S; Côté, IM. (2014) Linking removal targets to the ecological effects of invaders: a predictive model and field test.Ecological Applications 24: 1311-1322 Linking removal targets to the ecological effects of invaders: a predictive model and field test
ecological model; eradication; exotic species; lionfish; marine management; metabolic scaling theory; population control; predation; productivity; Pterois miles; Pterois volitans; size-based analysis
Species invasions have a range of negative effects on recipient ecosystems, and many occur at a scale and magnitude that preclude complete eradication. When complete extirpation is unlikely with available management resources, an effective strategy may be to suppress invasive populations below levels predicted to cause undesirable ecological change. We illustrated this approach by developing and testing targets for the control of invasive Indo-Pacific lionfish (Pterois volitans and P. miles) on Western Atlantic coral reefs. We first developed a size-structured simulation model of predation by lionfish on native fish communities, which we used to predict threshold densities of lionfish beyond which native fish biomass should decline. We then tested our predictions by experimentally manipulating lionfish densities above or below reef-specific thresholds, and monitoring the consequences for native fish populations on 24 Bahamian patch reefs over 18 months. We found that reducing lionfish below predicted threshold densities effectively protected native fish community biomass from predation-induced declines. Reductions in density of 25-92%, depending on the reef, were required to suppress lionfish below levels predicted to overconsume prey. On reefs where lionfish were kept below threshold densities, native prey fish biomass increased by 50-70%. Gains in small (<6 cm) size classes of native fishes translated into lagged increases in larger size classes over time. The biomass of larger individuals (>15 cm total length), including ecologically important grazers and economically important fisheries species, had increased by 10-65% by the end of the experiment. Crucially, similar gains in prey fish biomass were realized on reefs subjected to partial and full removal of lionfish, but partial removals took 30% less time to implement. By contrast, the biomass of small native fishes declined by >50% on all reefs with lionfish densities exceeding reef-specific thresholds. Large inter-reef variation in the biomass of prey fishes at the outset of the study, which influences the threshold density of lionfish, means that we could not identify a single rule of thumb for guiding control efforts. However, our model provides a method for setting reef-specific targets for population control using local monitoring data. Our work is the first to demonstrate that for ongoing invasions, suppressing invaders below densities that cause environmental harm can have a similar effect, in terms of protecting the native ecosystem on a local scale, to achieving complete eradication. DOI PubMed
77. Heupel, MR; Knip, DM; Simpfendorfer, CA; Dulvy, NK. (2014) Sizing up the ecological role of sharks as predators.Marine Ecology Progress Series 495: 291-298 Sizing up the ecological role of sharks as predators
Top-down control; Predator-prey interactions; Predation risk; Home range; Ecology of fear
The decline of predators in a variety of ecosystems has transformed community structure through mesopredator release and trophic cascades. Elasmobranch fishes, one of the earth's most ubiquitous and diverse clade of predatory species, provide a model group for defining marine predator roles. We consider whether the ecological predatory role of sharks is adequately defined by terrestrial-derived notions of apex-and mesopredation. Indeterminate growth and ontogenetic diet shifts may mean species-level classification of predatory roles is inadequate. We propose that examining the trophic level and body size of species might be the most pragmatic and informative way to define the ecological roles of predators. DOI
76. Sunday, JM; Bates, AE; Kearney, MR; Colwell, RK; Dulvy, NK; Longino, JT; Huey, RB. (2014) Thermal-safety margins and the necessity of thermoregulatory behavior across latitude and elevation.Proceedings of the National Academy of Sciences of the United States of America 111: 5610-5615 Thermal-safety margins and the necessity of thermoregulatory behavior across latitude and elevation
macrophysiology; operative temperature; climate sensitivity
Physiological thermal-tolerance limits of terrestrial ectotherms often exceed local air temperatures, implying a high degree of thermal safety (an excess of warm or cold thermal tolerance). However, air temperatures can be very different from the equilibrium body temperature of an individual ectotherm. Here, we compile thermal-tolerance limits of ectotherms across a wide range of latitudes and elevations and compare these thermal limits both to air and to operative body temperatures (theoretically equilibrated body temperatures) of small ectothermic animals during the warmest and coldest times of the year. We show that extreme operative body temperatures in exposed habitats match or exceed the physiological thermal limits of most ectotherms. Therefore, contrary to previous findings using air temperatures, most ectotherms do not have a physiological thermal-safety margin. They must therefore rely on behavior to avoid overheating during the warmest times, especially in the lowland tropics. Likewise, species living at temperate latitudes and in alpine habitats must retreat to avoid lethal cold exposure. Behavioral plasticity of habitat use and the energetic consequences of thermal retreats are therefore critical aspects of species' vulnerability to climate warming and extreme events. DOI
75. Anderson, SC; Cooper, AB; Dulvy, NK. (2013) Ecological prophets: quantifying metapopulation portfolio effects.Methods in Ecology and Evolution 4: 971-981 Ecological prophets: quantifying metapopulation portfolio effects
TAYLORS POWER-LAW; DIVERSITY-STABILITY RELATIONSHIPS; STATISTICAL INEVITABILITY; TEMPORAL STABILITY; FISH POPULATIONS; TIME-SERIES; BIODIVERSITY; VARIABILITY; DYNAMICS; PRODUCTIVITY
1. A financial portfolio metaphor is often used to describe how population diversity can increase temporal stability of a group of populations. The portfolio effect (PE) refers to the stabilizing effect from a population acting as a group or portfolio' of diverse subpopulations instead of a single homogeneous population or asset'. A widely used measure of the PE (the average-CV PE) implicitly assumes that the slope (z) of a log-log plot of mean temporal abundance and variance (Taylor's power law) equals two. 2. Existing theory suggests an additional unexplored empirical PE that accounts for z, the mean-variance PE. We use a theoretical and empirical approach to explore the strength and drivers of the PE for metapopulations when we account for Taylor's power law compared with when we do not. Our empirical comparison uses data from 51 metapopulations and 1070 subpopulations across salmon, moths and reef fishes. 3. Ignoring Taylor's power law may overestimate the stabilizing effect of population diversity for metapopulations. The disparity between the metrics is greatest at low z values where the average-CV PE indicates a strong PE. Compared with the mean-variance method, the average-CV PE estimated a stronger PE in 84% of metapopulations by up to sevenfold. The divergence between the methods was strongest for reef fishes (1.0 < z < 1.7) followed by moths (1.5 < z < 1.9). The PEs were comparable for salmon where z approximate to 2. 4. We outline practical recommendations for estimating ecological PEs based on research questions, study systems and available data. Because most PEs were stabilizing and diversity can be slow to restore, our meta-analysis of metapopulations suggests that the safest management approach is to conserve biological complexity. DOI
73. Hocking, MD; Dulvy, NK; Reynolds, JD; Ring, RA; Reimchen, TE. (2013) Salmon subsidize an escape from a size spectrum.Proceedings of the Royal Society B-Biological Sciences 280 Salmon subsidize an escape from a size spectrum
SPECIES ABUNDANCE DISTRIBUTIONS; BODY MASS RELATIONSHIPS; STRUCTURED FOOD WEBS; PACIFIC SALMON; POPULATION-DENSITY; ENERGY USE; COMMUNITIES; ECOSYSTEMS; PREDATION; NUTRIENTS
A general rule in ecology is that the abundance of species or individuals in communities sharing a common energy source decreases with increasing body size. However, external energy inputs in the form of resource subsidies can modify this size spectrum relationship. Here, we provide the first test of how a marine resource subsidy can affect size spectra of terrestrial communities, based on energy derived from Pacific salmon carcasses affecting a forest soil community beside streams in western Canada. Using both species-based and individual approaches, we found size structuring in this forest soil community, and transient community-wide doubling of standing biomass in response to energy pulses from Pacific salmon carcasses. One group of species were clear outliers in the middle of the size spectrum relationship: larval calliphorid and dryomyzid flies, which specialize on salmon carcasses, and which showed a tenfold increase in biomass in their size class when salmon were available. Thus, salmon subsidize their escape from the size spectrum. These results suggest that using a size-based perspective of resource subsidies can provide new insights into the structure and functioning of food webs. DOI
72. Juan-Jorda, MJ; Mosqueira, I; Freire, J; Dulvy, NK. (2013) The Conservation and Management of Tunas and Their Relatives: Setting Life History Research Priorities.PLOS One 8 The Conservation and Management of Tunas and Their Relatives: Setting Life History Research Priorities
MACKEREL SCOMBER-JAPONICUS; SOUTHERN BLUEFIN TUNA; EXTINCTION RISK; MARINE FISHES; INTRASPECIFIC VARIATION; REPRODUCTIVE-BIOLOGY; THUNNUS-ORIENTALIS; AGE-DETERMINATION; GROWTH; WATERS
Scombrids (tunas, bonitos, Spanish mackerels and mackerels) support important fisheries in tropical, subtropical and temperate waters around the world, being one of the most economically- and socially-important marine species globally. Their sustainable exploitation, management and conservation depend on accurate life history information for the development of quantitative fisheries stock assessments, and in the fishery data-poor situations for the identification of vulnerable species. Here, we assemble life history traits (maximum size, growth, longevity, maturity, fecundity, spawning duration and spawning interval) for the 51 species of scombrids globally. We identify major biological gaps in knowledge and prioritize life history research needs in scombrids based on their biological gaps in knowledge, the importance of their fisheries and their current conservation status according to the International Union for Conservation of Nature Red List. We find that the growth and reproductive biology of tunas and mackerel species have been more extensively studied than for Spanish mackerels and bonitos, although there are notable exceptions in all groups. We also reveal that reproductive biology of species, particular fecundity, is the least studied biological aspect in scombrids. We identify two priority groups, including 32 species of scombrids, and several populations of principal market tunas, for which life history research should be prioritized following the species-specific life history gaps identified in this study in the coming decades. By highlighting the important gaps in biological knowledge and providing a priority setting for life history research in scombrid species this study provides guidance for management and conservation and serves as a guide for biologists and resource managers interested in the biology, ecology, and management of scombrid species. DOI
71. Pardo, SA; Cooper, AB; Dulvy, NK. (2013) Avoiding fishy growth curves.Methods in Ecology and Evolution 4: 353-360 Avoiding fishy growth curves
GULF-OF-MEXICO; LIFE-HISTORY; BIOLOGICAL PARAMETERS; MULTIMODEL INFERENCE; HAMMERHEAD SHARK; GEAR SELECTIVITY; ATLANTIC-OCEAN; AGE; MODEL; SIZE
Somatic growth is a fundamental property of living organisms, and is of particular importance for species with indeterminate growth that can change in size continuously throughout their life. For example, fishes can increase in size by 26 orders of magnitude during their lifetime, resulting in changes in production, consumption and function at the ecosystem scale. Within species, growth rates are traded off against other life-history parameters, hence an accurate description of growth is essential to understand the comparative demography, productivity, fisheries yield and extinction risk of populations and species. The growth trajectory of indeterminate growing sharks and rays (elasmobranchs) and bony fishes (teleosts) is usually modelled using a three-parameter logarithmic function, the von Bertalanffy growth function (VBGF), to describe the total length of the average individual at any given age. Recently, however, a two-parameter form has gained popularity. Rather than being estimated in the model fitting process, the third y-intercept parameter (L0) of the VBGF has been interpreted as being biologically equivalent to, and thus fixed as, the empirically estimated size at birth. We tested the equivalence assumption that L0 is the same or similar to size at birth by comparing empirical estimates of size at birth available from the literature with estimates of L0 from published data from elasmobranchs, and found that even though there is an overlap of values, there is a high degree of variability between them. We calculate the bias in the growth coefficient (k) of the VBGF by comparison between the two- and three-parameter estimation methods. We show that slight deviations in fixed L0 can cause considerable bias in growth estimates in the two-parameter VBGF while providing no benefit even when L0 matches the true value. We show that the effect of this biased growth estimate has profound consequences for fisheries stock status. We strongly recommend the use of the three-parameter VBGF and discourage use of the two-parameter VBGF because it results in substantially biased growth estimates even with slight variations in the value of fixed L0. DOI
70. Blanchard, JL; Jennings, S; Holmes, R; Harle, J; Merino, G; Allen, JI; Holt, J; Dulvy, NK; Barange, M. (2012) Potential consequences of climate change for primary production and fish production in large marine ecosystems.Philosophical Transactions of the Royal Society B-Biological Sciences 367: 2979-2989 Potential consequences of climate change for primary production and fish production in large marine ecosystems
global environmental change; benthic-pelagic coupling; fisheries ecology; marine macroecology; marine communities; size spectrum
Existing methods to predict the effects of climate change on the biomass and production of marine communities are predicated on modelling the interactions and dynamics of individual species, a very challenging approach when interactions and distributions are changing and little is known about the ecological mechanisms driving the responses of many species. An informative parallel approach is to develop size-based methods. These capture the properties of food webs that describe energy flux and production at a particular size, independent of species' ecology. We couple a physical-biogeochemical model with a dynamic, size-based food web model to predict the future effects of climate change on fish biomass and production in 11 large regional shelf seas, with and without fishing effects. Changes in potential fish production are shown to most strongly mirror changes in phytoplankton production. We project declines of 30-60% in potential fish production across some important areas of tropical shelf and upwelling seas, most notably in the eastern Indo-Pacific, the northern Humboldt and the North Canary Current. Conversely, in some areas of the high latitude shelf seas, the production of pelagic predators was projected to increase by 28-89%. DOI
69. Chin A, White J, Dulvy NK. (2012) Aquatic conservation: Environment in Queensland at risk.Nature 490: 176. Aquatic conservation: Environment in Queensland at risk
In the state of Queensland, Australia, hard-won environmental protections are under threat.
In April this year, Queensland elected a new government that is pro-development and pro-mining. These activities have been burgeoning over the past few years, prompting the United Nations Educational, Scientific and Cultural Organization (UNESCO) to investigate whether the Great… DOI
68. Juan-Jordá, M.J., Mosqueira, I., Freire, J. & Dulvy, N.K. (2012) Life in 3-D: life history strategies in tunas, mackerels and bonitos.Reviews in Fish Biology and FisheriesLife in 3-D: life history strategies in tunas, mackerels and bonitos
Sexual dimorphism
Life history trade-offs
Mortality
Data-poor species
Data-poor methods
Conservation
Mammals
Life history data set
The scombrids (tunas, bonitos, Spanish mackerels and mackerels) sustain some of the most important fisheries in the world and their sustainable management depends on better understanding of their life history strategies. Here, we first assemble life history information on maximum size, growth, longevity, maturity, fecundity and spawning duration and interval for all scombrid species. Second we characterize their life history patterns and trait co-variation and evaluate how many principal axes of trait variation underlie scombrid life history strategies. Most of their life history variation can be explained along three axes or dimensions: size, speed, and reproductive schedule. Body size governs the first axis ranking species along a small-large continuum. The second axis was mostly influenced by time-related traits, such as longevity, growth rates, spawning duration, time between spawning events, ranking species along a slow-fast continuum of life histories. Scombrid species with the slowest life histories such as Atlantic bluefin tuna Thunnus thynnus and Atlantic mackerel Scomber scombrus tend to inhabit more temperate waters while species with faster life histories such as yellowfin tuna Thunnus albacares and short mackerel Rastrelliger brachysoma are typically found in more tropical waters. The third axis comprises the negative relationship between number of eggs produced at length of maturity and rate in gain of fecundity with size describing the schedule of reproductive allocation which reflects a fundamental trade-off between reproduction and growth. Finally, in addition we show that the life history strategies of scombrids conform more closely to the Periodic and Opportunistic strategists within the triangular model of fish life histories. DOI
67. Keith, SA; Webb, TJ; Bohning-Gaese, K; Connolly, SR; Dulvy, NK; Eigenbrod, F; Jones, KE; Price, T; Redding, DW; Owens, IPF; Isaac, NJB. (2012) What is macroecology?Biology Letters 8: 904-906 What is macroecology?
macroecology; spatial scale; process-based model; theory; ecosystem; disease
The symposium 'What is Macroecology?' was held in London on 20 June 2012. The event was the inaugural meeting of the Macroecology Special Interest Group of the British Ecological Society and was attended by nearly 100 scientists from 11 countries. The meeting reviewed the recent development of the macroecological agenda. The key themes that emerged were a shift towards more explicit modelling of ecological processes, a growing synthesis across systems and scales, and new opportunities to apply macroecological concepts in other research fields. DOI
66. McClenachan, L; Cooper, AB; Carpenter, KE; Dulvy, NK. (2012) Extinction risk and bottlenecks in the conservation of charismatic marine species.Conservation Letters 5: 73-80 Extinction risk and bottlenecks in the conservation of charismatic marine species
CITES; climate change; elasmobranchs; fishing impacts; IUCN Red List; reef fish; taxonomic bias
The oceans face a biodiversity crisis, but the degree and scale of extinction risk remains poorly characterized. Charismatic species are most likely to garner greatest support for conservation and thus provide a best-case scenario of the status of marine biodiversity. We summarize extinction risk and diagnose impediments to successful conservation for 1,568 species in 16 families of marine animals in the movie Finding Nemo. Sixteen percent (1234%) of those that have been evaluated are threatened, ranging from 9% (728%) of bony fishes to 100% (83100%) of marine turtles. A lack of scientific knowledge impedes analysis of threat status for invertebrates, which have 1,000 times fewer conservation papers than do turtles. Legal protection is severely deficient for sharks and rays; only 8% of threatened species in our analysis are protected. Extinction risk among wide-ranging taxa is higher than most terrestrial groups, suggesting a different conservation focus is required in the sea. DOI
65. Merino, G; Barange, M; Blanchard, JL; Harle, J; Holmes, R; Allen, I; Allison, EH; Badjeck, MC; Dulvy, NK; Holt, J; Jennings, S; Mullon, C; Rodwell, LD. (2012) Can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate?Global Environmental Change-Human and Policy Dimensions 22: 795-806 Can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate?
Global environmental change; Fish production; Fisheries; Aquaculture; Adaptation
Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products. (C) 2012 Elsevier Ltd. All rights reserved. DOI
64. Porszt, EJ; Peterman, RM; Dulvy, NK; Cooper, AB; Irvine, JR. (2012) Reliability of Indicators of Decline in Abundance.Conservation Biology 26: 894-904 Reliability of Indicators of Decline in Abundance
COSEWIC; IUCN; receiver operating characteristic (ROC); sockeye salmon; threat indicators; caracteristica de operacion del receptor; COR; COSEWIC; indicadores de amenaza; IUCN; Oncorhynchus nerka
Although there are many indicators of endangerment (i.e., whether populations or species meet criteria that justify conservation action), their reliability has rarely been tested. Such indicators may fail to identify that a population or species meets criteria for conservation action (false negative) or may incorrectly show that such criteria have been met (false positive). To quantify the rate of both types of error for 20 commonly used indicators of declining abundance (threat indicators), we used receiver operating characteristic curves derived from historical (19382007) data for 18 sockeye salmon (Oncorhynchus nerka) populations in the Fraser River, British Columbia, Canada. We retrospectively determined each population's yearly status (reflected by change in abundance over time) on the basis of each indicator. We then compared that population's status in a given year with the status in subsequent years (determined by the magnitude of decline in abundance across those years). For each sockeye population, we calculated how often each indicator of past status matched subsequent status. No single threat indicator provided error-free estimates of status, but indicators that reflected the extent (i.e., magnitude) of past decline in abundance (through comparison of current abundance with some historical baseline abundance) tended to better reflect status in subsequent years than the rate of decline over the previous 3 generations (a widely used indicator). We recommend that when possible, the reliability of various threat indicators be evaluated with empirical analyses before such indicators are used to determine the need for conservation action. These indicators should include estimates from the entire data set to take into account a historical baseline. DOI
63. Sunday, JM; Bates, AE; Dulvy, NK. (2012) Thermal tolerance and the global redistribution of animals.Nature Climate Change 2: 686-690 Thermal tolerance and the global redistribution of animals
The redistribution of life on Earth has emerged as one of the most significant biological responses to anthropogenic climate warming(1-3). Despite being one of the most long-standing puzzles in ecology(4), we still have little understanding of how temperature sets geographic range boundaries(5). Here we show that marine and terrestrial ectotherms differ in the degree to which they fill their potential latitudinal ranges, as predicted from their thermal tolerance limits. Marine ectotherms more fully occupy the extent of latitudes tolerable within their thermal tolerance limits, and are consequently predicted to expand at their poleward range boundaries and contract at their equatorward boundaries with climate warming. In contrast, terrestrial ectotherms are excluded from the warmest regions of their latitudinal range; thus, the equatorward, or 'trailing' range boundaries, may not shift consistently towards the poles with climate warming. Using global observations of climate-induced range shifts, we test this prediction and show that in the ocean, shifts at both range boundaries have been equally responsive, whereas on land, equatorward range boundaries have lagged in response to climate warming. These results indicate that marine species' ranges conform more closely to their limits of thermal tolerance, and thus range shifts will be more predictable and coherent. However, on land, warmer range boundaries are not at equilibrium with heat tolerance. Understanding the relative contribution of factors other than temperature in controlling equatorward range limits is critical for predicting distribution changes, with implications for population and community viability. DOI
61. Alvarez-Filip L., Gill J.A., Dulvy N.K. (2011) Complex reef architecture supports more small-bodied fishes and longer food chains on Caribbean reefs.Ecosphere 2, art118 Complex reef architecture supports more small-bodied fishes and longer food chains on Caribbean reefs
Coral community shifts towards reefs dominated by stress-resistant corals have contributed to rapid declines in the architectural complexity of reefs throughout the Caribbean. Complex reef architecture provides important niches and refuges for many reef fishes and thus widespread declines in reef complexity could have important consequences for the structure and function of fish assemblages. We explore the influence of reef architecture on fish assemblages by comparing the size and trophic structure of reef fishes along a 20 km-long 15-reef gradient of coral cover, coral species dominance and architectural complexity in Cozumel, Mexico. Our results show that reefs with high architectural complexity, in particular those dominated by robust Montastraea corals, supported fish assemblages with larger numbers of individuals in the smallest size classes (<20 cm) and longer food chains (higher mean trophic levels). The association between coral complexity and fish communities is highly size-structured and is greatest for smallest size classes. The greater abundance of both small fish and the key early life stages of larger fishes on more complex reefs suggests that architectural complexity may influence entire reef fish assemblages, even though larger fish are less dependent on reef complexity. Key reef-building corals such as Montastraea are thus likely to be disproportionately important for maintaining reef fish communities, and shifts in Caribbean coral communities may compromise fish recruitment and truncate food chains, reducing resilience and inhibiting reef recovery from degradation.PDF DOI
60. Alvarez-Filip, L; Côté, IM; Gill, JA; Watkinson, AR; Dulvy, NK. (2011) Region-wide temporal and spatial variation in Caribbean reef architecture: is coral cover the whole story?Global Change Biology 17: 2470-2477 Region-wide temporal and spatial variation in Caribbean reef architecture: is coral cover the whole story?
climate change; ecosystem services; foundation species; habitat loss; reef degradation
The architectural complexity of coral reefs is largely generated by reef-building corals, yet the effects of current regional-scale declines in coral cover on reef complexity are poorly understood. In particular, both the extent to which declines in coral cover lead to declines in complexity and the length of time it takes for reefs to collapse following coral mortality are unknown. Here we assess the extent of temporal and spatial covariation between coral cover and reef architectural complexity using a Caribbean-wide dataset of temporally replicated estimates spanning four decades. Both coral cover and architectural complexity have declined rapidly over time, with little evidence of a time-lag. However, annual rates of change in coral cover and complexity do not covary, and levels of complexity vary greatly among reefs with similar coral cover. These findings suggest that the stressors influencing Caribbean reefs are sufficiently severe and widespread to produce similar regional-scale declines in coral cover and reef complexity, even though reef architectural complexity is not a direct function of coral cover at local scales. Given that architectural complexity is not a simple function of coral cover, it is important that conservation monitoring and restoration give due consideration to both architecture and coral cover. This will help ensure that the ecosystem services supported by architectural complexity, such as nutrient recycling, dissipation of wave energy, fish production and diversity, are maintained and enhanced. DOI
59. Alvarez-Filip, L; Dulvy, NK; Côté, IM; Watkinson, AR; Gill, JA. (2011) Coral identity underpins architectural complexity on Caribbean reefs.Ecological Applications 21: 2223-2231 Coral identity underpins architectural complexity on Caribbean reefs
biodiversity; coral; Cozumel; Mexico; dominance; functional groups; habitat complexity; landscape ecology; reef
The architectural complexity of ecosystems can greatly influence their capacity to support biodiversity and deliver ecosystem services. Understanding the components underlying this complexity can aid the development of effective strategies for ecosystem conservation. Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic change is shifting communities toward reefs dominated by stress-resistant coral species, which are often less architecturally complex. With the regionwide decline in reef fish abundance, it is becoming increasingly important to understand changes in coral reef community structure and function. We quantify the influence of coral composition, diversity, and morpho-functional traits on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef architectural complexity increases with coral cover and species richness, it is highest on sites that are low in taxonomic evenness and dominated by morpho-functionally important, reef-building coral genera, particularly Montastraea. Sites with similar coral community composition also tend to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to be determined by the same key species across sites. Our findings provide support for prioritizing and protecting particular reef types, especially those dominated by key reef-building corals, in order to enhance reef complexity. DOI
58. Alvarez-Filip, L; Gill, JA; Dulvy, NK; Perry, AL; Watkinson, AR; Côté, IM. (2011) Drivers of region-wide declines in architectural complexity on Caribbean reefs.Coral Reefs 30: 1051-1060 Drivers of region-wide declines in architectural complexity on Caribbean reefs
Coral bleaching; Drivers of change; Environmental change; Ecosystem services; Habitat complexity; Hurricanes; Marine reserves; Reef degradation
Severe declines in the cover of live hard coral on reefs have been reported worldwide, and in the Caribbean region, the architectural complexity of coral reefs has also declined markedly. While the drivers of coral cover loss are relatively well understood, little is known about the drivers of regional-scale declines in architectural complexity. We have used a dataset of 49 time series reporting reef architectural complexity to explore the effect of hurricanes, coral bleaching and fishing on Caribbean-wide annual rates of change in reef complexity. Hurricane impacts greatly influence reef complexity, with the most rapid rates of decline in complexity occurring at sites impacted during their survey period, and with lower rates of loss occurring at unimpacted sites. Reef architectural complexity did not change significantly following mass bleaching events (in a time frame of < 5 years) or positive thermal anomalies. Although the rates of change in architectural complexity were similar in and out of marine protected areas (MPAs), significant declines in complexity were observed inside but not outside of MPAs, possibly because reductions in fishing can lead to increased bioerosion by herbivores within MPAs. Our findings suggest that major drivers of coral mortality, such as coral bleaching, do not influence reef architectural complexity in the short term (< 5 years). Instead, direct physical impacts and reef bioerosion appear to be important drivers of the widespread loss of architecturally complex reefs in the Caribbean. DOI
57. Chassot, E; Bonhommeau, S; Reygondeau, G; Nieto, K; Polovina, JJ; Huret, M; Dulvy, NK; Demarcq, H. (2011) Satellite remote sensing for an ecosystem approach to fisheries management.ICES Journal of Marine Science 68 Satellite remote sensing for an ecosystem approach to fisheries management
ecosystem approach; fisheries; mesoscale; satellite; tracking
Satellite remote sensing (SRS) of the marine environment has become instrumental in ecology for environmental monitoring and impact assessment, and it is a promising tool for conservation issues. In the context of an ecosystem approach to fisheries management (EAFM), global, daily, systematic, high-resolution images obtained from satellites provide a good data source for incorporating habitat considerations into marine fish population dynamics. An overview of the most common SRS datasets available to fishery scientists and state-of-the-art data-processing methods is presented, focusing on recently developed techniques for detecting mesoscale features such as eddies, fronts, filaments, and river plumes of major importance in productivity enhancement and associated fish aggregation. A comprehensive review of remotely sensed data applications in fisheries over the past three decades for investigating the relationships between oceanographic conditions and marine resources is provided, emphasizing how synoptic and information-rich SRS data have become instrumental in ecological analyses at community and ecosystem scales. Finally, SRS data, in conjunction with automated in situ data-acquisition systems, can provide the scientific community with a major source of information for ecosystem modelling, a key tool for implementing an EAFM. DOI
56. Juan-Jorda, MJ; Mosqueira, I; Cooper, AB; Freire, J; Dulvy, NK. (2011) Global population trajectories of tunas and their relatives.Proceedings of the National Academy of Sciences of the United States of America 108: 20650-20655 Global population trajectories of tunas and their relatives
Tunas and their relatives dominate the world's largest ecosystems and sustain some of the most valuable fisheries. The impacts of fishing on these species have been debated intensively over the past decade, giving rise to divergent views on the scale and extent of the impacts of fisheries on pelagic ecosystems. We use all available age-structured stock assessments to evaluate the adult biomass trajectories and exploitation status of 26 populations of tunas and their relatives (17 tunas, 5 mackerels, and 4 Spanish mackerels) from 1954 to 2006. Overall, populations have declined, on average, by 60% over the past half century, but the decline in the total adult biomass is lower (52%), driven by a few abundant populations. The trajectories of individual populations depend on the interaction between life histories, ecology, and fishing pressure. The steepest declines are exhibited by two distinct groups: the largest, longest lived, highest value temperate tunas and the smaller, short-lived mackerels, both with most of their populations being overexploited. The remaining populations, mostly tropical tunas, have been fished down to approximately maximum sustainable yield levels, preventing further expansion of catches in these fisheries. Fishing mortality has increased steadily to the point where around 12.5% of the tunas and their relatives are caught each year globally. Overcapacity of these fisheries is jeopardizing their long-term sustainability. To guarantee higher catches, stabilize profits, and reduce collateral impacts on marine ecosystems requires the rebuilding of overexploited populations and stricter management measures to reduce overcapacity and regulate threatening trade. DOI
55. Mull, CG; Yopak, KE; Dulvy, NK. (2011) Does more maternal investment mean a larger brain? Evolutionary relationships between reproductive mode and brain size in chondrichthyans.Marine and Freshwater Research 62: 567-575 Does more maternal investment mean a larger brain? Evolutionary relationships between reproductive mode and brain size in chondrichthyans
allometry; encephalisation; pGLS; relative brain size; reproductive mode
Chondrichthyans have the most diverse array of reproductive strategies of any vertebrate group, ranging from egg-laying to live-bearing with placental matrotrophy. Matrotrophy is defined as additional maternal provisioning beyond the yolk to the developing neonate; in chondrichthyans, this occurs through a range of mechanisms including uterine milk, oophagy, uterine cannibalism and placentotrophy. Chondrichthyans also exhibit a wide range of relative brain sizes and highly diverse patterns of brain organisation. Brains are energetically expensive to produce and maintain, and represent a major energetic constraint during early life in vertebrates. In mammals, more direct maternal-fetal placental connections have been associated with larger brains (steeper brain-body allometric scaling relationships). We test for a relationship between reproductive mode and relative brain size across 85 species from six major orders of chondrichthyans by using several phylogenetic comparative analyses. Ordinary least-squares (OLS) and reduced major axis (RMA) regression of body mass versus brain mass suggest that increased maternal investment results in a larger relative brain size. Our findings were supported by phylogenetic generalised least-squares models (pGLS), which also highlighted that these results vary with evolutionary tempo, as described by different branch-length assumptions. Across all analyses, maximum body size had a significant influence on the relative brain size, with large-bodied species (body mass > 100 kg) having relatively smaller brains. The present study suggests that there may be a link between reproductive investment and relative brain size in chondrichthyans; however, a more definitive test requires a better-resolved phylogeny and a more nuanced categorisation of the level of maternal investment in chondrichthyans. DOI
54. Salomon, AK; Gaichas, SK; Jensen, OP; Agostini, VN; Sloan, NA; Rice, J; McClanahan, TR; Ruckelshaus, MH; Levin, PS; Dulvy, NK; Babcock, EA. (2011) BRIDGING THE DIVIDE BETWEEN FISHERIES AND MARINE CONSERVATION SCIENCE.Bulletin of Marine Science 87: 251-274 BRIDGING THE DIVIDE BETWEEN FISHERIES AND MARINE CONSERVATION SCIENCE
Researchers from traditionally disparate disciplines and practitioners with typically incongruent mandates have begun working together to better understand and solve marine conservation and sustainable yield problems. Conservation practitioners are recognizing the need to achieve conservation goals in seascapes that are a source of livelihood and food security, while fisheries management is realizing that achieving economically and ecologically sustainable fisheries requires an understanding of the role of biodiversity and ecosystem dynamics in fishery production. Yet, tensions still exist due to the unique histories, epistemologies, cultures, values, and quantitative techniques of fisheries and marine conservation science, and the often-divergent objectives of the institutions and organizations these academic disciplines inform. While there is general agreement on what needs to be achieved (less overfishing, recovery of depleted fish stocks, reduction in bycatch and habitat impacts, jobs, food production), specific objectives and how best to achieve them remain contentious and unresolved. By analyzing three contemporary yet controversial marine policies (ecosystem-based fishery management, marine protected areas, and catch shares) and specific case studies, we demonstrate how both fisheries and marine conservation science can be used to provide clear scientific advice to practitioners and provide empirical evidence of the benefits of bridging the disciplinary divide. Finally, we discuss future prospects for collaboration in an emerging issue at the nexus of conservation and fishery management: eco-certification. Drawing on lessons learned from these empirical examples, we outline general processes necessary for clearly defining multiple conservation and fisheries objectives in working seascapes. By bridging the divide, we illuminate the process of navigating trade-offs between multiple objectives in a finite world. DOI
53. Simpfendorfer, CA; Heupel, MR; White, WT; Dulvy, NK. (2011) The importance of research and public opinion to conservation management of sharks and rays: a synthesis.Marine and Freshwater Research 62: 518-527 The importance of research and public opinion to conservation management of sharks and rays: a synthesis
chondrichthyes; research priorities; sustainable use
Growing concern for the world's shark and ray populations is driving the need for greater research to inform conservation management. A change in public perception, from one that we need to protect humans from sharks to one where we must protect sharks from humans, has added to calls for better management. The present paper examines the growing need for research for conservation management of sharks and rays by synthesising information presented in this Special Issue from the 2010 Sharks International Conference and by identifying future research needs, including topics such as taxonomy, life history, population status, spatial ecology, environmental effects, ecosystem role and human impacts. However, this biological and ecological research agenda will not be sufficient to fully secure conservation management. There is also a need for research to inform social and economic sustainability. Effective conservation management will be achieved by setting clear priorities for research with the aid of stakeholders, implementing well designed research projects, building the capacity for research, and clearly communicating the results to stakeholders. If this can be achieved, it will assure a future for this iconic group, the ecosystems in which they occur and the human communities that rely on them. DOI
52. Sparks, TH; Butchart, SHM; Balmford, A; Bennun, L; Stanwell-Smith, D; Walpole, M; Bates, NR; Bomhard, B; Buchanan, GM; Chenery, AM; Collen, B; Csirke, J; Diaz, RJ; Dulvy, NK; Fitzgerald, C; Kapos, V; Mayaux, P; Tierney, M; Waycott, M; Wood, L; Green, RE. (2011) Linked indicator sets for addressing biodiversity loss.Oryx 45: 411-419 Linked indicator sets for addressing biodiversity loss
2010 target; CBD; Convention on Biological Diversity; ecosystem services; humid tropical forest; marine fisheries; response
The target adopted by world leaders of significantly reducing the rate of biodiversity loss by 2010 was not met but this stimulated a new suite of biodiversity targets for 2020 adopted by the Parties to the Convention on Biological Diversity (CBD) in October 2010. Indicators will be essential for monitoring progress towards these targets and the CBD will be defining a suite of relevant indicators, building on those developed for the 2010 target. Here we argue that explicitly linked sets of indicators offer a more useful framework than do individual indicators because the former are easier to understand, communicate and interpret to guide policy. A Response-Pressure-State-Benefit framework for structuring and linking indicators facilitates an understanding of the relationships between policy actions, anthropogenic threats, the status of biodiversity and the benefits that people derive from it. Such an approach is appropriate at global, regional, national and local scales but for many systems it is easier to demonstrate causal linkages and use them to aid decision making at national and local scales. We outline examples of linked indicator sets for humid tropical forests and marine fisheries as illustrations of the concept and conclude that much work remains to be done in developing both the indicators and the causal links between them. DOI
51. Sunday, JM; Bates, AE; Dulvy, NK. (2011) Global analysis of thermal tolerance and latitude in ectotherms.Proceedings of the Royal Society B-Biological Sciences 278: 1823-1830 Global analysis of thermal tolerance and latitude in ectotherms
macroecology; macrophysiology; thermal tolerance breadth; latitude; thermal niche; climate variability hypothesis
A tenet of macroecology is that physiological processes of organisms are linked to large-scale geographical patterns in environmental conditions. Species at higher latitudes experience greater seasonal temperature variation and are consequently predicted to withstand greater temperature extremes. We tested for relationships between breadths of thermal tolerance in ectothermic animals and the latitude of specimen location using all available data, while accounting for habitat, hemisphere, methodological differences and taxonomic affinity. We found that thermal tolerance breadths generally increase with latitude, and do so at a greater rate in the Northern Hemisphere. In terrestrial ectotherms, upper thermal limits vary little while lower thermal limits decrease with latitude. By contrast, marine species display a coherent poleward decrease in both upper and lower thermal limits. Our findings provide comprehensive global support for hypotheses generated from studies at smaller taxonomic subsets and geographical scales. Our results further indicate differences between terrestrial and marine ectotherms in how thermal physiology varies with latitude that may relate to the degree of temperature variability experienced on land and in the ocean. DOI
50. Webb, TJ; Dulvy, NK; Jennings, S; Polunin, NVC. (2011) The birds and the seas: body size reconciles differences in the abundance-occupancy relationship across marine and terrestrial vertebrates.Oikos 120: 537-549 The birds and the seas: body size reconciles differences in the abundance-occupancy relationship across marine and terrestrial vertebrates
Despite some fundamental differences in production processes and the ecology of consumer species on land and in the sea, further understanding of pattern and process in both biomes might be gained by applying common methods of macroecological analysis. We develop methods that reconcile apparent differences in abundance and occupancy for marine and terrestrial vertebrates, as exemplified by fish and birds. These recognize and take account of those aspects of the life history and ecology of marine and terrestrial animals that influence their abundance, distribution and trophic role. When abundance and occupancy are averaged within species over time we show that variation within a region is less for birds than fish, but when abundance and occupancy are averaged over space, the difference between birds and fish disappears. Further, we develop size rather than species-structured abundance-occupancy relationships for fish assemblages and demonstrate that patterns of intra-size class variation that are very similar to intraspecific variation in bird species, over both time and space. We argue that this result reflects the relative importance of body size and species identity respectively in determining trophic roles in marine and terrestrial environments. Selection of the appropriate analytical unit on land (species) and in the sea (size) helps to reconcile apparently divergent macroecological patterns, especially when these are driven by contrasting patterns of energy acquisition and use. DOI
49. Wiegand, J; Hunter, E; Dulvy, NK. (2011) Are spatial closures better than size limits for halting the decline of the North Sea thornback ray, Raja clavata?Marine and Freshwater Research 62: 722-733 Are spatial closures better than size limits for halting the decline of the North Sea thornback ray, Raja clavata?
by-catch; discard; elasmobranch; length restrictions; management strategy evaluation; marine reserve
A key challenge of the ecosystem approach to fisheries management is to sustain viable populations of large-bodied less-productive vulnerable elasmobranchs that are the by-catch of fisheries that target more productive species. The North Sea population of the thornback ray (Raja clavata) is now mainly confined to the Thames Estuary and surrounding SW North Sea, which is subject to a flatfish trawl fishery. We explored the relative effectiveness of seasonal closures versus size-based landing restrictions using a four-season age-structured model. More than a third of adult thornback rays are currently removed by fishing each year, and without effective management, a further 90% decline within 30 years is likely. A three-season closure of the Thames Estuary was the shortest closure that ensured thornback ray recovery and minimal loss of fishery yield. Minimum and maximum landing size restrictions are nearly as effective at recovering thornback rays but less so at improving yield. While long seasonal closures and full marine protected areas are more effective at ensuring the recovery of thornback rays, length restrictions may be simpler to implement under the current institutional framework and may have less impact on the multispecies trawl fisheries operating in the area. DOI
48. Abernethy, KE; Trebilcock, P; Kebede, B; Allison, EH; Dulvy, NK. (2010) Fuelling the decline in UK fishing communities?ICES Journal of Marine Science 67: 1076-1085 Fuelling the decline in UK fishing communities?
adaptation and coping strategies; fisher behaviour; fisheries; fuel prices; resilience; uncertainty
Volatile fuel prices are a threat to the viability of UK fishing communities. The economic and social impacts of rising fuel costs for fishers and communities in southwest England are examined. Fuel prices doubled between early 2007 and mid-2008, whereas fish prices remained relatively stable throughout as a result of the price-setting power of seafood buyers. It was the fishers who absorbed the increased costs, resulting in significant loss of income, reduced job security, and problems in recruiting crew. All gear types were affected, but fishers using towed gears were most adversely impacted. Fishing vessels with recent investment have greater fuel efficiency, so appeared to be more able to cope and to adapt to increased fuel costs. Fishing behaviour also altered as skippers attempted to increase fuel efficiency at the cost of reduced catches. Most skippers reported fishing closer to port, reducing their exploratory fishing, and ceasing experimentation with fishing gears with lesser environmental impact. Therefore, a threat to fishing community viability may have linked environmental effects. The impacts of this fuel price volatility foreshadow a likely future impact of rising fuel prices attributable to climate change adaptation and mitigation and forecasts of rising oil prices. Without proactive planning and policy development, rising fuel prices have the potential to cause job losses and economic hardship additional to problems that may arise from poor management and stock decline, in all fishing-related sectors of the industry. DOI
47. Badjeck, MC; Allison, EH; Halls, AS; Dulvy, NK. (2010) Impacts of climate variability and change on fishery-based livelihoods.Marine Policy 34: 375-383 Impacts of climate variability and change on fishery-based livelihoods
Fisheries; Livelihoods; Climate change; Climate variability; Adaptation
There is increasing concern over the consequences of global warming for the food security and livelihoods of the world's 36 million fisherfolk and the nearly 1.5 billion consumers who rely oil fish for more than 20% of their dietary animal protein. With mounting evidence of the impacts of climate variability and change oil aquatic ecosystems, the resulting impacts oil fisheries livelihoods are likely to be significant, but remain a neglected area in climate adaptation policy. Drawing upon our research and the available literature, and using a livelihoods framework, this paper synthesizes the pathways through which climate variability and change impact fisherfolk livelihoods at the household and community level. We identify current and potential adaptation strategies and explore the wider implications for local livelihoods, fisheries management and climate policies. Responses to climate change can be anticipatory or reactive and should include: (1) management approaches and policies that build the livelihood asset base, reducing vulnerability to multiple stressors, including climate change; (2) an understanding of current response mechanisms to climate variability and other shocks in order to inform planned adaptation; (3) a recognition of the opportunities that climate change could bring to the sector; (4) adaptive strategies designed with a multi-sector perspective; and (5) a recognition of fisheries potential contribution to mitigation efforts. (C) 2009 Elsevier Ltd. All rights reserved. DOI
46. Chassot, E; Bonhommeau, S; Dulvy, NK; Melin, F; Watson, R; Gascuel, D; Le Pape, O. (2010) Global marine primary production constrains fisheries catches.Ecology Letters 13: 495-505 Global marine primary production constrains fisheries catches
Bottom-up; Large Marine Ecosystem; quantile regression; sustainable fishing
P>Primary production must constrain the amount of fish and invertebrates available to expanding fisheries; however the degree of limitation has only been demonstrated at regional scales to date. Here we show that phytoplanktonic primary production, estimated from an ocean-colour satellite (SeaWiFS), is related to global fisheries catches at the scale of Large Marine Ecosystems, while accounting for temperature and ecological factors such as ecosystem size and type, species richness, animal body size, and the degree and nature of fisheries exploitation. Indeed we show that global fisheries catches since 1950 have been increasingly constrained by the amount of primary production. The primary production appropriated by current global fisheries is 17-112% higher than that appropriated by sustainable fisheries. Global primary production appears to be declining, in some part due to climate variability and change, with consequences for the near future fisheries catches. DOI
45. Hoffmann, M; Hilton-Taylor, C; Angulo, A; Bohm, M; Brooks, TM; Butchart, SHM; Carpenter, KE; Chanson, J; Collen, B; Cox, NA; Darwall, WRT; Dulvy, NK; Harrison, LR; Katariya, V; Pollock, CM; Quader, S; Richman, NI; Rodrigues, ASL; Tognelli, MF; Vie, JC; Aguiar, JM; Allen, DJ; Allen, GR; Amori, G; Ananjeva, NB; Andreone, F; Andrew, P; Ortiz, ALA; Baillie, JEM; Baldi, R; Bell, BD; Biju, SD; Bird, JP; Black-Decima, P; Blanc, JJ; Bolanos, F; Bolivar, W; Burfield, IJ; Burton, JA; Capper, DR; Castro, F; Catullo, G; Cavanagh, RD; Channing, A; Chao, NL; Chenery, AM; Chiozza, F; Clausnitzer, V; Collar, NJ; Collett, LC; Collette, BB; Fernandez, CFC; Craig, MT; Crosby, MJ; Cumberlidge, N; Cuttelod, A; Derocher, AE; Diesmos, AC; Donaldson, JS; Duckworth, JW; Dutson, G; Dutta, SK; Emslie, RH; Farjon, A; Fowler, S; Freyhof, J; Garshelis, DL; Gerlach, J; Gower, DJ; Grant, TD; Hammerson, GA; Harris, RB; Heaney, LR; Hedges, SB; Hero, JM; Hughes, B; Hussain, SA; Icochea, J; Inger, RF; Ishii, N; Iskandar, DT; Jenkins, RKB; Kaneko, Y; Kottelat, M; Kovacs, KM; Kuzmin, SL; La Marca, E; Lamoreux, JF; Lau, MWN; Lavilla, EO; Leus, K; Lewison, RL; Lichtenstein, G; Livingstone, SR; Lukoschek, V; Mallon, DP; McGowan, PJK; McIvor, A; Moehlman, PD; Molur, S; Alonso, AM; Musick, JA; Nowell, K; Nussbaum, RA; Olech, W; Orlov, NL; Papenfuss, TJ; Parra-Olea, G; Perrin, WF; Polidoro, BA; Pourkazemi, M; Racey, PA; Ragle, JS; Ram, M; Rathbun, G; Reynolds, RP; Rhodin, AGJ; Richards, SJ; Rodriguez, LO; Ron, SR; Rondinini, C; Rylands, AB; de Mitcheson, YS; Sanciangco, JC; Sanders, KL; Santos-Barrera, G; Schipper, J; Self-Sullivan, C; Shi, YC; Shoemaker, A; Short, FT; Sillero-Zubiri, C; Silvano, DL; Smith, KG; Smith, AT; Snoeks, J; Stattersfield, AJ; Symes, AJ; Taber, AB; Talukdar, BK; Temple, HJ; Timmins, R; Tobias, JA; Tsytsulina, K; Tweddle, D; Ubeda, C; Valenti, SV; van Dijk, PP; Veiga, LM; Veloso, A; Wege, DC; Wilkinson, M; Williamson, EA; Xie, F; Young, BE; Akcakaya, HR; Bennun, L; Blackburn, TM; Boitani, L; Dublin, HT; da Fonseca, GAB; Gascon, C; Lacher, TE; Mace, GM; Mainka, SA; McNeely, JA; Mittermeier, RA; Reid, GM; Rodriguez, JP; Rosenberg, AA; Samways, MJ; Smart, J; Stein, BA; Stuart, SN. (2010) The Impact of Conservation on the Status of the World's Vertebrates.Science 330: 1503-1509 The Impact of Conservation on the Status of the World's Vertebrates
Using data for 25,780 species categorized on the International Union for Conservation of Nature Red List, we present an assessment of the status of the world's vertebrates. One-fifth of species are classified as Threatened, and we show that this figure is increasing: On average, 52 species of mammals, birds, and amphibians move one category closer to extinction each year. However, this overall pattern conceals the impact of conservation successes, and we show that the rate of deterioration would have been at least one-fifth again as much in the absence of these. Nonetheless, current conservation efforts remain insufficient to offset the main drivers of biodiversity loss in these groups: agricultural expansion, logging, overexploitation, and invasive alien species. DOI
44. MacNeil, MA; Graham, NAJ; Cinner, JE; Dulvy, NK; Loring, PA; Jennings, S; Polunin, NVC; Fisk, AT; McClanahan, TR. (2010) Transitional states in marine fisheries: adapting to predicted global change.Philosophical Transactions of the Royal Society B-Biological Sciences 365: 3753-3763 Transitional states in marine fisheries: adapting to predicted global change
climate change; fish communities; social-ecological systems; biodiversity
Global climate change has the potential to substantially alter the production and community structure of marine fisheries and modify the ongoing impacts of fishing. Fish community composition is already changing in some tropical, temperate and polar ecosystems, where local combinations of warming trends and higher environmental variation anticipate the changes likely to occur more widely over coming decades. Using case studies from the Western Indian Ocean, the North Sea and the Bering Sea, we contextualize the direct and indirect effects of climate change on production and biodiversity and, in turn, on the social and economic aspects of marine fisheries. Climate warming is expected to lead to (i) yield and species losses in tropical reef fisheries, driven primarily by habitat loss; (ii) community turnover in temperate fisheries, owing to the arrival and increasing dominance of warm-water species as well as the reduced dominance and departure of cold-water species; and (iii) increased diversity and yield in Arctic fisheries, arising from invasions of southern species and increased primary production resulting from ice-free summer conditions. How societies deal with such changes will depend largely on their capacity to adapt-to plan and implement effective responses to change-a process heavily influenced by social, economic, political and cultural conditions. DOI
43. Sheppard, C; Al-Husiani, M; Al-Jamali, F; Al-Yamani, F; Baldwin, R; Bishop, J; Benzoni, F; Dutrieux, E; Dulvy, NK; Durvasula, SRV; Jones, DA; Loughland, R; Medio, D; Nithyanandan, M; Pilling, GM; Polikarpov, I; Price, ARG; Purkis, S; Riegl, B; Saburova, M; Namin, KS; Taylor, O; Wilson, S; Zainal, K. (2010) The Gulf: A young sea in decline.Marine Pollution Bulletin 60: 13-38 The Gulf: A young sea in decline
Arabian Gulf; Persian Gulf; Coral reefs; Mangroves; Sea grass; Climate stresses; Temperature rise; Sedimentation; Fisheries; Development; Gulf War; Oil pollution; Pollution
This review examines the substantial changes that have taken place in marine habitats and resources of the Gulf over the past decade. The habitats are especially interesting because of the naturally high levels of temperature and salinity stress they experience, which is important in a changing world climate. However, the extent of all natural habitats is changing and their condition deteriorating because of the rapid development of the region and, in some cases from severe, episodic warming episodes. Major impacts come from numerous industrial, infrastructure-based, and residential and tourism development activities, which together combine, synergistically in some cases, to cause the observed deterioration in most benthic habitats. Substantial sea bottom dredging for material and its deposition in shallow water to extend land or to form a basis for huge developments, directly removes large areas of shallow, productive habitat, though in some cases the most important effect is the accompanying sedimentation or changes to water flows and conditions. The large scale of the activities compared to the relatively shallow and small size of the water body is a particularly important issue. Important from the perspective of controlling damaging effects is the limited cross-border collaboration and even intra-country collaboration among government agencies and large projects. Along with the accumulative nature of impacts that occur, even where each project receives environmental assessment or attention, each is treated more or less alone, rarely in combination. However, their combination in such a small, biologically interacting sea exacerbates the overall deterioration. Very few similar areas exist which face such a high concentration of disturbance, and the prognosis for the Gulf continuing to provide abundant natural resources is poor. (C) 2009 Published by Elsevier Ltd. DOI
42. Wilson, SK; Fisher, R; Pratchett, MS; Graham, NAJ; Dulvy, NK; Turner, RA; Cakacaka, A; Polunin, NVC. (2010) Habitat degradation and fishing effects on the size structure of coral reef fish communities.Ecological Applications 20: 442-451 Habitat degradation and fishing effects on the size structure of coral reef fish communities
climate change; community disturbance and recovery; coral reef fisheries; habitat complexity
Overfishing and habitat degradation through climate change pose the greatest threats to sustainability of marine resources on coral reefs. We examined how changes in fishing pressure and benthic habitat composition influenced the size spectra of island-scale reef fish communities in Lau, Fiji. Between 2000 and 2006 fishing pressure declined in the Lau Islands due to declining human populations and reduced demand for fresh fish. At the same time, coral cover declined and fine-scale architectural complexity eroded due to coral bleaching and outbreaks of crown-of-thorns starfish, Acanthaster planci. We examined the size distribution of reef fish communities using size spectra analysis, the linearized relationship between abundance and body size class. Spatial variation in fishing pressure accounted for 31% of the variation in the slope of the size spectra in 2000, higher fishing pressure being associated with a steeper slope, which is indicative of fewer large-bodied fish and/or more small-bodied fish. Conversely, in 2006 spatial variation in habitat explained 53% of the variation in the size spectra slopes, and the relationship with fishing pressure was much weaker (similar to 12% of variation) than in 2000. Reduced cover of corals and lower structural complexity was associated with less steep size spectra slopes, primarily due to reduced abundance of fish <20 cm. Habitat degradation will compound effects of fishing on coral reefs as increased fishing reduces large-bodied target species, while habitat loss results in fewer small-bodied juveniles and prey that replenish stocks and provide dietary resources for predatory target species. Effective management of reef resources therefore depends on both reducing fishing pressure and maintaining processes that encourage rapid recovery of coral habitat.
41. Allison, EH; Perry, AL; Badjeck, MC; Adger, WN; Brown, K; Conway, D; Halls, AS; Pilling, GM; Reynolds, JD; Andrew, NL; Dulvy, NK. (2009) Vulnerability of national economies to the impacts of climate change on fisheries.Fish and Fisheries 10: 173-196 Vulnerability of national economies to the impacts of climate change on fisheries
COD GADUS-MORHUA; NINO SOUTHERN-OSCILLATION; GLOBAL FOOD SECURITY; SEA-LEVEL RISE; ADAPTIVE CAPACITY; NORTH-SEA; EL-NINO; ECOLOGICAL RESILIENCE; POPULATION-DYNAMICS; OCEAN ACIDIFICATION
Anthropogenic global warming has significantly influenced physical and biological processes at global and regional scales. The observed and anticipated changes in global climate present significant opportunities and challenges for societies and economies. We compare the vulnerability of 132 national economies to potential climate change impacts on their capture fisheries using an indicator-based approach. Countries in Central and Western Africa (e.g. Malawi, Guinea, Senegal, and Uganda), Peru and Colombia in north-western South America, and four tropical Asian countries (Bangladesh, Cambodia, Pakistan, and Yemen) were identified as most vulnerable. This vulnerability was due to the combined effect of predicted warming, the relative importance of fisheries to national economies and diets, and limited societal capacity to adapt to potential impacts and opportunities. Many vulnerable countries were also among the world's least developed countries whose inhabitants are among the world's poorest and twice as reliant on fish, which provides 27% of dietary protein compared to 13% in less vulnerable countries. These countries also produce 20% of the world's fish exports and are in greatest need of adaptation planning to maintain or enhance the contribution that fisheries can make to poverty reduction. Although the precise impacts and direction of climate-driven change for particular fish stocks and fisheries are uncertain, our analysis suggests they are likely to lead to either increased economic hardship or missed opportunities for development in countries that depend upon fisheries but lack the capacity to adapt.Website DOI
40. Alvarez-Filip, L; Dulvy, NK; Gill, JA; Côté, IM; Watkinson, AR. (2009) Flattening of Caribbean coral reefs: region-wide declines in architectural complexity.Proceedings of the Royal Society B-Biological Sciences 276: 3019-3025 Flattening of Caribbean coral reefs: region-wide declines in architectural complexity
HABITAT COMPLEXITY; FISH ASSEMBLAGES; CLIMATE-CHANGE; SEA-URCHIN; IMPACTS; ABUNDANCE; ECOSYSTEMS; HURRICANES; DIVERSITY; MORTALITY
Coral reefs are rich in biodiversity, in large part because their highly complex architecture provides shelter and resources for a wide range of organisms. Recent rapid declines in hard coral cover have occurred across the Caribbean region, but the concomitant consequences for reef architecture have not been quantified on a large scale to date. We provide, to our knowledge, the first region-wide analysis of changes in reef architectural complexity, using nearly 500 surveys across 200 reefs, between 1969 and 2008. The architectural complexity of Caribbean reefs has declined nonlinearly with the near disappearance of the most complex reefs over the last 40 years. The flattening of Caribbean reefs was apparent by the early 1980s, followed by a period of stasis between 1985 and 1998 and then a resumption of the decline in complexity to the present. Rates of loss are similar on shallow (<6 m), mid-water (6-20 m) and deep (>20 m) reefs and are consistent across all five subregions. The temporal pattern of declining architecture coincides with key events in recent Caribbean ecological history: the loss of structurally complex Acropora corals, the mass mortality of the grazing urchin Diadema antillarum and the 1998 El Nino Southern Oscillation-induced worldwide coral bleaching event. The consistently low estimates of current architectural complexity suggest regional-scale degradation and homogenization of reef structure. The widespread loss of architectural complexity is likely to have serious consequences for reef biodiversity, ecosystem functioning and associated environmental services. DOI
39.Dulvy NK, Hyde K, Heymans JJ, Chassot E, Platt T & Sherman K. (2009) Climate change, ecosystem variability and fisheries productivity.In: Applications of Remote Sensing in Fisheries and Aquaculture (Eds. Platt T & Sathyendranath S). International Ocean-Colour Coordinating Group Halifax, Nova Scotia.Climate change, ecosystem variability and fisheries productivity.
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38.Dulvy NK, Pinnegar JK and Reynolds JD. (2009) Holocene extinctions in the sea.In Holocene Extinctions in the Sea. (Ed S.T. Turvey), Pp. 129-150. Oxford University Press, Oxford.Holocene extinctions in the sea.
36. Newson, S. E., S. Mendes, H. Q. P. Crick, N. K. Dulvy, J. D. R. Houghton, G. C. Hays, A. M. Hutson, C. D. Macleod, G. J. Pierce, and R. A. Robinson. (2009) Indicators of the impact of climate change on migratory species.Endangered Species Research 7: 101–113 Indicators of the impact of climate change on migratory species.
DOI
35. Vergnon, R; Dulvy, NK; Freckleton, RP. (2009) Niches versus neutrality: uncovering the drivers of diversity in a species-rich community.Ecology Letters 12: 1079-1090 Niches versus neutrality: uncovering the drivers of diversity in a species-rich community
ABUNDANCE DISTRIBUTIONS; RELATIVE ABUNDANCE; BIODIVERSITY; PHYTOPLANKTON; COEXISTENCE; DYNAMICS; PLANKTON; ECOLOGY; MODEL; SIZE
Ecological models suggest that high diversity can be generated by purely niche-based, purely neutral or by a mixture of niche-based and neutral ecological processes. Here, we compare the degree to which four contrasting hypotheses for coexistence, ranging from niche-based to neutral, explain species richness along a body mass niche axis. We derive predictions from these hypotheses and confront them with species body-mass patterns in a highly sampled marine phytoplankton community. We find that these patterns are consistent only with a mechanism that combines niche and neutral processes, such as the emergent neutrality mechanism. In this work, we provide the first empirical evidence that a niche-neutral model can explain niche space occupancy pattern in a natural species-rich community. We suggest this class of model may be a useful hypothesis for the generation and maintenance of species diversity in other size-structured communities. DOI
34.Dulvy, NK; Baum, JK; Clarke, S; Compagno, LJV; Cortes, E; Domingo, A; Fordham, S; Fowler, S; Francis, MP; Gibson, C; Martinez, J; Musick, JA; Soldo, A; Stevens, JD; Valenti, S. (2008) You can swim but you can't hide: the global status and conservation of oceanic pelagic sharks and rays.Aquatic Conservation-Marine and Freshwater Ecosystems 18: 459-482 You can swim but you can't hide: the global status and conservation of oceanic pelagic sharks and rays
biodiversity conservation; demography; elasmobranch; life histories; blue shark; white shark; porbeagle; thresher shark; tuna; billfish NORTH-ATLANTIC OCEAN; DASYATIS-VIOLACEA BONAPARTE; BIGEYE THRESHER SHARK; PRIONACE-GLAUCA; ISURUS-OXYRINCHUS; SHORTFIN MAKO; BLUE SHARK; REPRODUCTIVE-BIOLOGY; PACIFIC-OCEAN; NEW-ZEALAND
1. Fishing spans all oceans and the impact on ocean predators such as sharks and rays is largely unknown. A lack of data and complicated jurisdictional issues present particular challenges for assessing and conserving high seas biodiversity. It is clear, however, that pelagic sharks and rays of the open ocean are subject to high and often unrestricted levels of mortality from bycatch and targeted fisheries for their meat and valuable fins. 2. These species exhibit a wide range of life-history characteristics, but many have relatively low productivity and consequently relatively high intrinsic vulnerability to over-exploitation. The IUCN-World Conservation Union Red List criteria were used to assess the global status of 21 oceanic pelagic shark and ray species. 3. Three-quarters (16) of these species are classified as Threatened or Near Threatened. Eleven species are globally threatened with higher risk of extinction: the giant devilray is Endangered, ten sharks are Vulnerable and a further five species are Near Threatened. Threat status depends on the interaction between the demographic resilience of the species and intensity of fisheries exploitation. 4. Most threatened species, like the shortfin mako shark, have low population increase rates and suffer high fishing mortality throughout their range. Species with a lower risk of extinction have either fast, resilient life histories (e.g. pelagic stingray) or are species with slow, less resilient life histories but subject to fisheries management (e.g. salmon shark). 5. Recommendations, including implementing and enforcing firming bans and catch limits, are made to guide effective conservation and management of these sharks and rays. Copyright (c) 2008 John Wiley & Sons, Ltd. DOI
33.Dulvy, NK; Rogers, SI; Jennings, S; Stelzenmuller, V; Dye, SR; Skjoldal, HR. (2008) Climate change and deepening of the North Sea fish assemblage: a biotic indicator of warming seas.Journal of Applied Ecology 45: 1029-1039 Climate change and deepening of the North Sea fish assemblage: a biotic indicator of warming seas
climate change; habitat loss; invasive species; life-history trait; North Sea; regime shift; thermal preference
1. Climate change impacts have been observed on individual species and species subsets; however, it remains to be seen whether there are systematic, coherent assemblage-wide responses to climate change that could be used as a representative indicator of changing biological state. 2. European shelf seas are warming faster than the adjacent land masses and faster than the global average. We explore the year-by-year distributional response of North Sea bottom-dwelling (demersal) fishes to temperature change over the 25 years from 1980 to 2004. The centres of latitudinal and depth distributions of 28 fishes were estimated from species-abundance-location data collected on an annual fish monitoring survey. 3. Individual species responses were aggregated into 19 assemblages reflecting physiology (thermal preference and range), ecology (body size and abundance-occupancy patterns), biogeography (northern, southern and presence of range boundaries), and susceptibility to human impact (fishery target, bycatch and non-target species). 4. North Sea winter bottom temperature has increased by 1.6 degrees C over 25 years, with a 1 degrees C increase in 1988-1989 alone. During this period, the whole demersal fish assemblage deepened by similar to 3.6 m decade(-1) and the deepening was coherent for most assemblages. 5. The latitudinal response to warming was heterogeneous, and reflects (i) a northward shift in the mean latitude of abundant, widespread thermal specialists, and (ii) the southward shift of relatively small, abundant southerly species with limited occupancy and a northern range boundary in the North Sea. 6. Synthesis and applications. The deepening of North Sea bottom-dwelling fishes in response to climate change is the marine analogue of the upward movement of terrestrial species to higher altitudes. The assemblage-level depth responses, and both latitudinal responses, covary with temperature and environmental variability in a manner diagnostic of a climate change impact. The deepening of the demersal fish assemblage in response to temperature could be used as a biotic indicator of the effects of climate change in the North Sea and other semi-enclosed seas. DOI
32. Hiddink, JG; MacKenzie, BR; Rijnsdorp, A; Dulvy, NK; Nielsen, EE; Bekkevold, D; Heino, A; Lorance, P; Ojaveer, H. (2008) Importance of fish biodiversity for the management of fisheries and ecosystems.Fisheries Research 90: 6-8 Importance of fish biodiversity for the management of fisheries and ecosystems
fish; biodiversity; ecosystems; management COD RECRUITMENT; NORTH-SEA; POPULATION
A group of fisheries scientists participating in a European Union Network of Excellence (MARBEF) summarizes risks to the biodiversity of fish in European seas and recommends ways how existing fish diversity can be conserved, restored and managed. (C) 2008 Elsevier B.V. All rights reserved. DOI
31. Jennings, S; Melin, F; Blanchard, JL; Forster, RM; Dulvy, NK; Wilson, RW. (2008) Global-scale predictions of community and ecosystem properties from simple ecological theory.Proceedings of the Royal Society B-Biological Sciences 275: 1375-1383 Global-scale predictions of community and ecosystem properties from simple ecological theory
macroecology; metabolic ecology; food web; food chain; climate; production FISH PRODUCTION; FOOD WEBS; OCEAN; BIOMASS; SIZE; SEA; PHYTOPLANKTON; NORTHWESTERN; PREDATORS; ABUNDANCE
We show how theoretical developments in macroecology, life-history theory and food-web ecology can be combined to formulate a simple model for predicting the potential biomass, production, size and trophic structure of consumer communities. The strength of our approach is that it uses remote sensing data to predict properties of consumer communities in environments that are challenging and expensive to sample directly. An application of the model to the marine environment on a global scale, using primary production and temperature estimates from satellite remote sensing as inputs, suggests that the global biomass of marine animals more than 10(-5) g wet weight is 2.62 x 10(9) t (=8.16 g m(-2) ocean) and production is 1.00 x 10(10) t yr(-1) (31.15 g m(-2) yr(-1)). Based on the life-history theory, we propose and apply an approximation for distinguishing the relative contributions of different animal groups. Fish biomass and production, for example, are estimated as 8.99 x 10(8) t (2.80 g m(-2)) and 7.91 x 10(8) t yr(-1) (2.46 g m(-2) yr(-1)), respectively, and 50% of fish biomass is shown to occur in 17% of the total ocean area (8.22 g m(-2)). The analyses show that emerging ecological theory can be synthesized to set baselines for assessing human and climate impacts on global scales. DOI
30. Somerfield, PJ; Clarke, KR; Warwick, RM; Dulvy, NK. (2008) Average functional distinctness as a measure of the composition of assemblages.ICES Journal of Marine Science 65: 1462-1468 Average functional distinctness as a measure of the composition of assemblages
biodiversity; functional distinctness; marine; monitoring; relatedness; taxonomic distinctness MARINE BIOTIC INDEX; TAXONOMIC DISTINCTNESS; PHYLOGENETIC DIVERSITY; FISH COMMUNITIES; BIODIVERSITY; DISSIMILARITY
Indices are used to quantify change in the environment by reducing aspects of environmental complexity to numbers. Biodiversity indices are typically calculated using the numbers of species and their relative abundances. A recent advance has been the development of additional measures of diversity, such as phylogenetic diversity, based on relationships between organisms. The emerging paradigms of the importance of biodiversity to ecosystem services and the ecosystem approach to fishery management could be well served by the development of indicators of ecosystem functioning. We discuss how relatedness measures may be adapted to quantify aspects of community structure of relevance to ecosystem functioning, by combining information on species' occurrence, life history, and ecological traits. We present an index that reflects average functional distinctness within assemblages. We illustrate the approach using North Sea fish. Results reveal that average functional distinctness is not independent of taxonomic distinctness. This is expected, but the weakness of the relationship suggests that both indices may prove useful, because they are not constrained to convey the same information about samples. Both indices are shown to be weakly related to species richness, which was not expected. This is a consequence of differences in the frequencies of occurrence among species. DOI
29. Sutherland, WJ; Bailey, MJ; Bainbridge, IP; Brereton, T; Dick, JTA; Drewitt, J; Dulvy, NK; Dusic, NR; Freckleton, RP; Gaston, KJ; Gilder, PM; Green, RE; Heathwaite, AL; Johnson, SM; Macdonald, DW; Mitchell, R; Osborn, D; Owen, RP; Pretty, J; Prior, SV; Prosser, H; Pullin, AS; Rose, P; Stott, A; Tew, T; Thomas, CD; Thompson, DBA; Vickery, JA; Walker, M; Walmsley, C; Warrington, S; Watkinson, AR; Williams, RJ; Woodroffe, R; Woodroof, HJ. (2008) Future novel threats and opportunities facing UK biodiversity identified by horizon scanning.Journal of Applied Ecology 45: 821-833 Future novel threats and opportunities facing UK biodiversity identified by horizon scanning
conservation; conservation policy; decision making; environmental risk; nanotechnology NORTHERN EUROPEAN SEAS; CLIMATE-CHANGE; GREEN EXERCISE; MANAGEMENT; HEALTH; POLICY; NANOTECHNOLOGY; COUNTRYSIDE; QUESTIONS; RESOURCES
1. Horizon scanning is an essential tool for environmental scientists if they are to contribute to the evidence base for Government, its agencies and other decision makers to devise and implement environmental policies. The implication of not foreseeing issues that are foreseeable is illustrated by the contentious responses to genetically modified herbicide-tolerant crops in the UK, and by challenges surrounding biofuels, foot and mouth disease, avian influenza and climate change. 2. A total of 35 representatives from organizations involved in environmental policy, academia, scientific journalism and horizon scanning were asked to use wide consultation to identify the future novel or step changes in threats to, and opportunities for, biodiversity that might arise in the UK up to 2050, but that had not been important in the recent past. At least 452 people were consulted. 3. Cases for 195 submitted issues were distributed to all participants for comments and additions. All issues were scored (probability, hazard, novelty and overall score) prior to a 2-day workshop. Shortlisting to 41 issues and then the final 25 issues, together with refinement of these issues, took place at the workshop during another two rounds of discussion and scoring. 4. We provide summaries of the 25 shortlisted issues and outline the research needs. 5. We suggest that horizon scanning incorporating wide consultation with providers and users of environmental science is used by environmental policy makers and researchers. This can be used to identify gaps in knowledge and policy, and to identify future key issues for biodiversity, including those arising from outside the domains of ecology and biodiversity. 6. Synthesis and applications. Horizon scanning can be used by environmental policy makers and researchers to identify gaps in knowledge and policy. Drawing on the experience, expertise and research of policy advisors, academics and journalists, this exercise helps set the agenda for policy, practice and research. DOI
28. Wilson, SK; Fisher, R; Pratchett, MS; Graham, NAJ; Dulvy, NK; Turner, RA; Cakacaka, A; Polunin, NVC; Rushton, SP. (2008) Exploitation and habitat degradation as agents of change within coral reef fish communities.Global Change Biology 14: 2796-2809 Exploitation and habitat degradation as agents of change within coral reef fish communities
climate change; density dependence; disturbance; food webs; trophic cascades GREAT-BARRIER-REEF; SOUTH-EASTERN AUSTRALIA; TROPHIC CASCADES; CLIMATE-CHANGE; MARINE RESERVES; TOP-DOWN; BOTTOM-UP; FOOD WEBS; ECOSYSTEMS; FISHERIES
Over-exploitation and habitat degradation are the two major drivers of global environmental change and are responsible for local extinctions and declining ecosystem services. Here we compare the top-down effect of exploitation by fishing with the bottom-up influence of habitat loss on fish communities in the most diverse of ecological systems, coral reefs. Using a combination of multivariate techniques and path analyses, we illustrate that the relative importance of coral cover and fishing in controlling fish abundance on remote Fijian reefs varies between species and functional groups. A decline in branching Acropora coral is strongly associated with a decline in abundance of coral-feeding species, and a decrease in coral-associated habitat complexity, which has indirectly contributed to reduced abundance of small-bodied damselfish. In contrast, reduced fishing pressure, brought about by declining human populations and a shift to alternate livelihoods, is associated with increased abundance of some piscivores and fisheries target species. However, availability of prey is controlled by coral-associated habitat complexity and appears to be a more important driver of total piscivore abundance compared with fishing pressure. Effects of both fishing and coral loss are stronger on individual species than functional groups, as variation in the relative importance of fishing or coral loss among species within the same functional group attenuated the impact of either of these potential drivers at the functional level. Overall, fishing continues to have an influence on Fijian fish communities; however, habitat loss is currently the overriding agent of change. The importance of coral loss mediated by climate change is expected to have an increasing contribution to fish community dynamics, particularly in remote locations or where the influence of fishing is waning. DOI
27. Newton, K; Côté, IM; Pilling, GM; Jennings, S; Dulvy, NK. (2007) Current and future sustainability of island coral reef fisheries.Current Biology 17: 655-658 Current and future sustainability of island coral reef fisheries
Overexploitation is one of the principal threats to coral reef diversity, structure, function, and resilience [1, 2]. Although it is generally held that coral reef fisheries are unsustainable [3-5], little is known of the overall scale of exploitation or which reefs are overfished [6]. Here, on the basis of ecological footprints and a review of exploitation status [7, 8], we report widespread unsustainability of island coral reef fisheries. Over half (55%) of the 49 island countries considered are exploiting their coral reef fisheries in an unsustainable way. We estimate that total landings of coral reef fisheries are currently 64% higher than can be sustained. Consequently, the area of coral reef appropriated by fisheries exceeds the available effective area by similar to 75,000 km(2), or 3.7 times the area of Australia's Great Barrier Reef, and an extra 196,000 km(2) of coral reef may be required by 2050 to support the anticipated growth in human populations. The large overall imbalance between current and sustainable catches implies that management methods to reduce social and economic dependence on reef fisheries are essential to prevent the collapse of coral reef ecosystems while sustaining the well-being of burgeoning coastal populations. DOI
25. Blanchard, JL; Dulvy, NK; Jennings, S; Ellis, JR; Pinnegar, JK; Tidd, A; Kell, LT. (2005) Do climate and fishing influence size-based indicators of Celtic Sea fish community structure?ICES Journal of Marine Science 62 Do climate and fishing influence size-based indicators of Celtic Sea fish community structure?
Celtic Sea; climate; ecosystem indicators; fish communities; fishing effects; size spectrum
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24.Dulvy, NK; Jennings, S; Goodwin, NB; Grant, A; Reynolds, JD. (2005) Comparison of threat and exploitation status in North-East Atlantic marine populations.Journal of Applied Ecology 42: 883-891 Comparison of threat and exploitation status in North-East Atlantic marine populations
CITES; extinction risk; marine fisheries; minimum viable population; Red List
1. Threat listing of exploited marine species has been controversial because of the scientific uncertainty of extinction risk as well as the social, economic and political costs of management procedures that may be triggered by designation of species as threatened. 2. We applied three sets of threat criteria to 76 stocks (populations) of 21 exploited marine fish and invertebrate species. Two criteria sets were based on decline rates: World Conservation Union (IUCN A1) and the American Fisheries Society (AFS). The third set of criteria, based on population viability (IUCN E), was assessed using non-parametric simulation and two diffusion approximation methods. 3. We compared extinction risk outcomes (threatened or not) against the exploitation status of each stock as reported in fish stock assessments (inside or outside safe biological limits). For each combination of threat and exploitation we assessed the rate of hits, misses and false alarms. 4. Our analyses suggest that decline rate criteria provide risk categorizations consistent with population viability analyses when applied to exploited marine stocks. Nearly a quarter of the fish and invertebrate populations (n = 18) considered met one or more of the threat criteria. 5. None of the threat metrics produced false alarms, where sustainably exploited stocks were categorized as threatened. The quantitative IUCN E metrics produced higher hit rates than the decline rate metrics (IUCN A1 and AFS) and all of the metrics produced similar miss rates. However, the IUCN E methods could be applied to fewer stocks (12-14) compared with IUCN A1 decline rate and AFS criteria, both of which could be applied all 76 stocks. 6. Synthesis and applications. Threat criteria provide warnings of population collapse that are consistent with those provided in fisheries stock assessments. Our results suggest that scientists with different backgrounds and objectives should usually be able to agree on the stocks for which the most urgent management action is needed. Moreover, IUCN A1 decline rate metrics may provide useful indicators of population status when the information needed for full fisheries stock assessment is not available. DOI
23. Ellis, J; Dulvy, N; O'Brien, C; Sims, D; Southall, E. (2005) Shark, skate and ray research at the MBA and Cefas.Journal of the Marine Biological Association of the United Kingdom 85 Shark, skate and ray research at the MBA and Cefas
22. Ellis, J; Dulvy, NK; Jennings, S; Parker-Humphreys, M; Rogers, SI. (2005) Assessing the status of demersal elasmobranchs in UK waters: a review.Journal of the Marine Biological Association of the United Kingdom 85 Assessing the status of demersal elasmobranchs in UK waters: a review
21. Goodwin, NB; Dulvy, NK; Reynolds, JD. (2005) Macroecology of live-bearing in fishes: latitudinal and depth range comparisons with egg-laying relatives.Oikos 110: 209-218 Macroecology of live-bearing in fishes: latitudinal and depth range comparisons with egg-laying relatives
We examine how fishes with contrasting reproductive modes (egg-laying versus live-bearing) differ in geographic range size and distribution. One hypothesis based on dispersal suggests that egg-laying taxa should occupy a wider range of latitudes than live-bearing, whereas the opposite prediction has been derived from the idea that enhanced maternal input and a 'safe harbor' during development will enable live-bearers to occupy a wider range of latitudes and depths than egg-layers. Cross-species analysis supports the first hypothesis for teleosts, with egg-layers living in a wider range of latitudes than live-bearers but at lower latitudes, across a narrower depth range and at shallow depth. However, elasmobranchs show the opposite pattern, live-bearers having wider latitudinal ranges. Phylogenetic paired comparisons of sister egg-laying and live-bearing taxa confirm these contrasting patterns between teleosts and elasmobranchs. However, depth range, maximum latitude and depth do not differ with reproductive mode. Latitudinal range size increases with body size among all taxa. However, only teleosts have a positive relationship between body size and maximum latitude, depth and depth range, but this does not differ between reproductive modes. Egg-laying elasmobranchs have low dispersal, but live-bearers have not extended their maximum latitude or depth, despite the benefits of sheltered offspring. The differences in range size between egg-layers and live-bearers and the distinction between teleosts and elasmobranchs is consequence of contrasting mechanisms of dispersal and benefits of maternally buffered transport of developing offspring.
20. Graham, NAJ; Dulvy, NK; Jennings, S; Polunin, NVC. (2005) Size-spectra as indicators of the effects of fishing on coral reef fish assemblages.Coral Reefs 24 Size-spectra as indicators of the effects of fishing on coral reef fish assemblages
ecosystem based fishery management; size spectra; coral reef fisheries; community structure; indirect effects; fisheries management
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17. Reynolds, JD; Dulvy, NK; Goodwin, NB; Hutchings, JA. (2005) Biology of extinction risk in marine fishes.P Roy Soc B-Biol Sci 272: 2337-2344 Biology of extinction risk in marine fishes
fisheries; conservation; life histories; IUCN; CITES
We review interactions between extrinsic threats to marine fishes and intrinsic aspects of their biology that determine how populations and species respond to those threats. Information is available on the status of less than 5% of the world's approximately 15 500 marine fish species, most of which are of commercial importance. By 2001, based on data from 98 North Atlantic and northeast Pacific populations, marine fishes had declined by a median 65% in breeding biomass from known historic levels; 28 populations had declined by more than 80%. Most of these declines would be sufficient to warrant a status of threatened with extinction under international threat criteria. However, this interpretation is highly controversial, in part because of a perception that marine fishes have a suite of life history characteristics, including high fecundity and large geographical ranges, which might confer greater resilience than that shown by terrestrial vertebrates. We review 15 comparative analyses that have tested for these and other life history correlates of vulnerability in marine fishes. The empirical evidence suggests that large body size and late maturity are the best predictors of vulnerability to fishing, regardless of whether differences among taxa in fishing mortality are controlled; there is no evidence that high fecundity confers increased resilience. The evidence reviewed here is of direct relevance to the diverse criteria used at global and national levels by various bodies to assess threat status of fishes. Simple life history traits can be incorporated directly into quantitative assessment criteria, or used to modify the conclusions of quantitative assessments, or used as preliminary screening criteria for assessment of the similar to 95% of marine fish species whose status has yet to be evaluated either by conservationists or fisheries scientists.
15.Dulvy, NK; Ellis, JR; Goodwin, NB; Grant, A; Reynolds, JD; Jennings, S. (2004) Methods of assessing extinction risk in marine fishes.Fish and Fisheries 5: 255-276 Methods of assessing extinction risk in marine fishes
CITES; fish; IUCN; Red List; life history; refence points; threat
The decline and disappearance of species from large parts of their former geographical ran-e has become an important issue in fisheries ecology. There is a need to identify which species are at risk of extinction. The available approaches have been subject to considerable debate - particularly when applied to commercially exploited species. Here we have compiled methods that have been used or may be used for assessing threat status of marine organisms. We organize the methods according to the availability of data on the natural history, ecology and population biology of species. There are three general approaches to inferring or assessing extinction risk: (i) correlative approaches based on knowledge of life histories and ecology: (ii) time-series approaches that examine changes in abundance: and (iii) demographic approaches based on age- or stage-based schedules of vital rates and fisheries reference points. Many methods are well suited to species that are highly catchable and/or have relatively low productivity, but theory is less well developed for assessing extinction risk in species exhibiting narrow geographical distributions or ecological specialization. There is considerable variation in both definitions of extinction risk and the precision and defensibility of the available risk assessment methods, so we suggest a two-tiered approach for defining and assessing extinction risk. First. simple methods requiring a few easily estimated parameters are used to triage or rapidly assess large numbers of populations and species to identify potentially vulnerable populations or species. Second. the populations and species identified as vulnerable by this process can then be subject to more detailed and rigorous population analysis explicitly considering sources of error and uncertainty.
11.Dulvy, NK; Sadovy, Y; Reynolds, JD. (2003) Extinction vulnerability in marine populations.Fish and Fisheries 4: 25-64 Extinction vulnerability in marine populations
biodiversity; conservation; detection; fisheries; recovery; Red List; risk
Human impacts on the world's oceans have been substantial, leading to concerns about the extinction of marine taxa. We have compiled 133 local, regional and global extinctions of marine populations. There is typically a 53-year lag between the last sighting of an organism and the reported date of the extinction at whatever scale this has occurred. Most disappearances (80%) were detected using indirect historical comparative methods, which suggests that marine extinctions may have been underestimated because of low-detection power. Exploitation caused most marine losses at various scales (55%), followed closely by habitat loss (37%), while the remainder were linked to invasive species, climate change, pollution and disease. Several perceptions concerning the vulnerability of marine organisms appear to be too general and insufficiently conservative. Marine species cannot be considered less vulnerable on the basis of biological attributes such as high fecundity or large-scale dispersal characteristics. For commercially exploited species, it is often argued that economic extinction of exploited populations will occur before biological extinction, but this is not the case for non-target species caught in multispecies fisheries or species with high commercial value, especially if this value increases as species become rare. The perceived high potential for recovery, high variability and low extinction vulnerability of fish populations have been invoked to avoid listing commercial species of fishes under international threat criteria. However, we need to learn more about recovery, which may be hampered by negative population growth at small population sizes (Allee effect or depensation) or ecosystem shifts, as well as about spatial dynamics and connectivity of subpopulations before we can truly understand the nature of responses to severe depletions. The evidence suggests that fish populations do not fluctuate more than those of mammals, birds and butterflies, and that fishes may exhibit vulnerability similar to mammals, birds and butterflies. There is an urgent need for improved methods of detecting marine extinctions at various spatial scales, and for predicting the vulnerability of species.
8.Dulvy, NK; Reynolds, JD. (2002) Predicting extinction vulnerability in skates.Conservation Biology 16: 440-450 Predicting extinction vulnerability in skates
Relatively few marine fishes have been assessed tender World Conservation Union criteria, yet it is believed that marine fish extinction rates have been underestimated by one order of magnitude McKinney 1999). Given the paucity of data required for traditional assessment methods, we explored the use of potential correlates of extinction vulnerability to prioritize species for conservation assessment. We focused oil the world's 230 species of skates and rays (Rajidae) because they have been identified (is one of the most vulnerable groups of marine fishes, We searched for all documented cases of local extinction tend compiled it database of body size and latitudinal and depth ranges for all species for which data were available. We found that species that have disappeared from substantial parts of Their ranges ("locally extinct") have large body sizes compared with all other skates, bill that latitudinal and depth ranges were similar to those of other species. The body size correlate may be due to higher mortality rates and correlations with life-history parameters such as late age at maturity. We used the locally extinct species that held the smallest size or ranges as benchmarks to generate lists of other species that may be vulnerable. Body size generated the smallest species list (7), excluding the known local extinctions, compared with lists generated b), size of latitudinal (150) or depth range (63). Body size was the only trait that correctly identified the known local extinctions, suggesting that it is more useful them range sizes for identifying potentially vulnerable fishes, This provides a simple, objective method of prioritizing species for further assessment, which complements direct methods that are more data-intensive and time-consuming.
7. Goodwin, NB; Dulvy, NK; Reynolds, JD. (2002) Life-history correlates of the evolution of live bearing in fishes.Philosophical Transactions of the Royal Society B-Biological Sciences 357: 259-267 Life-history correlates of the evolution of live bearing in fishes
comparative method; reproduction; viviparity; phylogeny; shark; coelacanth
Selection for live bearing is thought to occur when the benefits of increasing offspring survival exceed the costs of reduced fecundity, mobility and the increased metabolic demands of carrying offspring throughout development. We present evidence that live bearing has evolved from egg laying 12 times in teleost (bony) fishes, bringing the total number of transitions to 21 to 22 times in all fishes, including elasmobranchs (sharks and rays). Live bearers produce larger offspring than egg layers in all of 13 independent comparisons for which data were available. However, contrary to our expectation there has not been a consistent reduction in fecundity; live bearers have fewer offspring in seven out of the 11 available comparisons. It was predicted that live bearers would have a larger body size, as this facilitates accommodation of developing offspring. This prediction was upheld in 14 out of 20 comparisons. However, this trend was driven by elasmobranchs, with large live bearers in seven out of eight comparisons. Thus, while the evolution of live bearing in elasmobranchs is correlated with predicted increases in offspring size and adult size, teleost live bearers do not have such a consistent suite of life-history correlates. This suggests that constraints or selection pressures on associated life histories may differ in live-bearing elasmobranchs and teleost fishes. DOI
6.Dulvy, NK; Metcalfe, JD; Glanville, J; Pawson, MG; Reynolds, JD. (2000) Fishery stability, local extinctions, and shifts in community structure in skates.Conservation Biology 14: 283-293 Fishery stability, local extinctions, and shifts in community structure in skates
Skates are arguably the most vulnerable of exploited marine fishes. Their vulnerability is often assessed by examining fisheries catch trends, but these data are not generally recorded on a species basis except in France. Aggregated skate catch statistics tend to exhibit more stable trends than those of other elasmobranch fisheries. We tested whether such apparent stability in aggregated catch trends could mask population declines of individual species. We examined two time series of species-specific surveys of a relatively stable skate fishery in the norhteast Atlantic. These surveys revealed the disappearance of two skate species, long-nose skate (Dipturus oxyrhinchus) and white skate (Rostroraja alba) and confirmed a previously documented decline of the common skate (D. batis). Of the remaining five skate species, the three larger ones have declined, whereas two smaller species have increased in abundance. The increase in abundance and biomass of the smaller species has resulted in the stability of the aggregated catch trends. Because there is significant dietary overlap among species, we suggest the increase in abundance of the smaller species may be due to competitive release as the larger species declined. A consequence of this kind of stability is that declining species cannot be detected without species-specific data, especially in taxa exhibiting competitive interactions. This may explain why previously documented disappearances of two species of skates went unnoticed for so long. The conservation of skates and other elasmobranchs requires species-specific monitoring and special attention to larger species.
5. Rickman, SJ; Dulvy, NK; Jennings, S; Reynolds, JD. (2000) Recruitment variation related to fecundity in marine fishes.Canadian Journal of Fisheries and Aquatic Sciences 57: 116-124 Recruitment variation related to fecundity in marine fishes
An understanding of the processes that control recruitment variation is central to explaining the population dynamics of fishes and predicting their responses to exploitation. Theory predicts that interannual variation in recruitment should be positively correlated with the fecundity of fish species, but empirical studies have not supported this hypothesis. Here, we adopt a phylogenetic comparative approach, which accounts for evolutionary relatedness among stocks and species, to investigate this relationship. We calculated the mean fecundity of fishes from 52 stocks at the mean length of maturity and related this to interannual recruitment variation. We found that in 13 of 14 comparisons between stocks or closely related species, the stocks with higher fecundity have higher recruitment variation. This was true whether or not we controlled for spawning stock size. However, when the analyses were repeated using a traditional cross-species approach, which did not account for the evolutionary relatedness of stocks, the relationships were not significant. This is the first empirical study to link fecundity with recruitment variation and suggests that fecundity is an important component of fish stock dynamics.
4. Stevens, JD; Bonfil, R; Dulvy, NK; Walker, PA. (2000) The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems.ICES Journal of Marine Science 57 The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems
community structure; ECOSIM; ecosystem; elasmobranchs; extinction; fishing effects; mass-balance model; population impacts; species replacement; species vulnerability; trophic interactions
3.Dulvy, NK; Reynolds, JD. (1997) Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays.Proceedings of the Royal Society of London Series B-Biological Sciences 264: 1309-1315 Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays
Sharks and rays are thought to have a large number of independent origins of live-bearing. We examined evolutionary transitions to live-bearing and maternal input to embryos in this subclass by optimizing reproductive characters onto a composite phylogeny. Egg-laying (40% of all species) is the likely ancestral reproductive mode for this clade, and there is evidence that live-bearing has evolved independently 9-10 times and maternal input 4-5 times. Most transitions (12-15) have been toward live-bearing with provisioning limited to yolk. These have occurred from egg-laying ancestors or live-bearing taxa that provide maternal input to embryos. Only 2-3 transitions have occurred in the other direction, i.e. away from yolk-only live-bearing. Egg-laying has evolved from live-bearing ancestors in skates, Rajidae (25% of all species) and possibly in the zebra shark, Stegostoma fasciata. Thus, although there has been an overall trend toward the evolution of live-bearing in elasmobranchs, the evolution of additional maternal input has been extremely labile.
