Fish assemblages and barriers in an urban stream network
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| Authors: | Favaro, C; Moore, JW |
| Year: | 2015 |
| Journal: | Freshwater Science 34: 991-1005 Article Link (DOI) |
| Title: | Fish assemblages and barriers in an urban stream network |
| Abstract: | Stream networks are vulnerable to fragmentation. Anthropogenic structures, such as dams and culverts, can isolate stream branches, potentially interrupting longitudinal gradients of fish distribution. The effect of single barriers is well documented, but the effect of multiple barriers in small streams is not as well characterized. We used a landscape approach and spatially continuous sampling across 2 y to examine the influence of anthropogenic structures on fish distributions in an urban stream network. After accounting for spatial autocorrelation, we found higher Coastal Cutthroat Trout (Oncorhynchus clarki clarki) and lower Prickly Sculpin (Cottus asper) densities at locations up-than downstream of multiple culverts. Culverts had species-and year-specific stepwise effects that overrode fish distribution patterns attributable to environmental gradients. Prickly Sculpin exhibited strong spatial autocorrelation in both years, whereas Coho Salmon (Oncorhynchus kisutch) had negligible spatial autocorrelation in one year, a result indicating that spatial structure depends on species and year. Reaches did not have consistent fish densities across years and showed high temporal variability of fish or their habitats. Spatially continuous sampling captured gradients and heterogeneity in fish distributions and highlighted how anthropogenic structures alter these gradients. Our study also revealed which culverts had the strongest influences on fish densities throughout the stream network. The study design used can inform riverscape-management approaches, which are needed to conserve stream biodiversity effectively. |
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