Migration links ocean-scale competition and local ocean conditions with exposure to farmed salmon to shape wild salmon dynamics.


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Authors: Connors, B.M., Braun, D.C., Peterman, R.M., Cooper, A.B., Reynolds, J.D., Dill, L.M., Ruggerone, G.T. & Krkosek, M.
Year: 2012
Journal: Conservation Letters 2012, 1-9    Website    Article Link (DOI)
Title: Migration links ocean-scale competition and local ocean conditions with exposure to farmed salmon to shape wild salmon dynamics.
Abstract: Climate, competition, and disease are well-recognized drivers of population
dynamics. These stressors can be intertwined by animal migrations, leading to
uncertainty about the roles of natural and anthropogenic factors in conservation
and resource management. We quantitatively assessed the four leading
hypotheses for an enigmatic long-term decline in productivity of Canada’s
iconic Fraser River sockeye salmon: (1) delayed density-dependence, (2) local
oceanographic conditions, (3) pathogen transmission from farmed salmon, and
(4) ocean-basin scale competition with pink salmon. Our findings suggest that
the long-term decline is primarily explained by competition with pink salmon,
which can be amplified by exposure to farmed salmon early in sockeye marine
life, and by a compensatory interaction between coastal ocean temperature
and farmed-salmon exposure. These correlative relationships suggest oceanicscale
processes, which are beyond the reach of current regulatory agencies,
may exacerbate local ecological processes that challenge the coexistence of
fisheries and aquaculture-based economies in coastal seas.
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