Salmon Migration
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Salmon populations in the Pacific Northwest declined significantly over the past 100 years. In response to this, local residents, scientists and managers pay closer attention to what salmon need for survival. To reproduce, salmon migrate upstream from the ocean to freshwater streams where they lay and fertilize their eggs, known as spawning. Dams are the most well known barriers to this upstream migration, but poor water quality, warm water temperatures and the timing of low and high flows can also hinder the migration [1, 2]. Salmon are particularly sensitive to warm temperatures and may not move upstream if the stream water is too warm [3,5,6]. The migration timing of salmon and other fish may be an important indicator of how climate conditions affect the Pacific Northwest’s ecosystem. The following graph [Figure b] presents the date on which half of the returning sockeye salmon have completed their upstream migration from the ocean to the freshwater streams above Lower Granite Dam (median migration date) [9].
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Median date of upstream adult sockeye salmon migration as recorded (gray 5 missing data) at Lower Granite Dam, the uppermost dam on the lower Snake River near the Washington/Idaho border
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This information covering 30 years suggests that sockeye salmon return to their freshwater streams about 1 day earlier in the spring each decade.
Within Idaho and the entire Pacific Northwest, salmon are recognized as a valuable natural resource. They are culturally important to the native tribes in the area and the local angling community. They are ecologically important as part of the natural food web. They also bring nutrients upstream as they migrate back from the ocean to the freshwater streams of Idaho. They are also of great economic importance to the state, bringing business through sport fishing and providing jobs in the fisheries. As a species that is sensitive to temperature, sockeye salmon are a good early indicator of more profound changes that may occur in aquatic systems. Salmon migration timing has the potential to indicate larger, more profound changes in the region, and help us identify linkages between physical and ecological systems.
Many factors besides just temperature influence migration. These factors include: stream flow, length of daylight, and the conditions in the ocean [4, 6]. Human activity also plays a role, including the construction and operation of dams, fish ladders, transportation of fish, and agricultural run-off that impacts water quality [5, 6].These complex factors make it difficult to identify direct cause and effect. Nevertheless, salmon deserve attention because they are a socially, culturally and economically relevant resource to the state of Idaho.
Within Idaho and the entire Pacific Northwest, salmon are recognized as a valuable natural resource. They are culturally important to the native tribes in the area and the local angling community. They are ecologically important as part of the natural food web. They also bring nutrients upstream as they migrate back from the ocean to the freshwater streams of Idaho. They are also of great economic importance to the state, bringing business through sport fishing and providing jobs in the fisheries. As a species that is sensitive to temperature, sockeye salmon are a good early indicator of more profound changes that may occur in aquatic systems. Salmon migration timing has the potential to indicate larger, more profound changes in the region, and help us identify linkages between physical and ecological systems.
Many factors besides just temperature influence migration. These factors include: stream flow, length of daylight, and the conditions in the ocean [4, 6]. Human activity also plays a role, including the construction and operation of dams, fish ladders, transportation of fish, and agricultural run-off that impacts water quality [5, 6].These complex factors make it difficult to identify direct cause and effect. Nevertheless, salmon deserve attention because they are a socially, culturally and economically relevant resource to the state of Idaho.
References
- Achord, S., R. W. Zabel, and B. P. Sandford. 2007. Migration timing, growth, and estimated parr-to-smolt survival rates of wild Snake River spring-summer Chinook salmon from the Salmon River basin, Idaho, to the Lower Snake River. Transactions of the American Fisheries Society 136:142–154.
- Hodgson, S., and T. P. Quinn. 2002. The timing of adult sockeye salmon migration into fresh water: adaptations by populations to prevailing thermal regimes. Canadian Journal of Zoology 80:542–555.
- Crozier, L. G., and R. W. Zabel. 2006. Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon. Journal of Animal Ecology 75:1100–1109.
- Rand, P. S., S. G. Hinch, J. Morrison, M. G. G. Foreman, M.J. MacNutt, J. S. Macdonald, M. C. Healey et al. 2006. Effects of river discharge, temperature, and future climates on energetics and mortality of adult migrating Fraser River sockeye salmon. Transactions of the American Fisheries Society 135:655–667.
- Crozier, L. G., R. W. Zabel, and A. F. Hamlet. 2008. Predicting differential effects of climate change at the population level with life-cycle models of spring Chinook salmon. Global Change Biology 14:236–249.
- Quinn, T. P., and D. J. Adams. 1996. Environmental changes affecting the migratory timing of American shad and sockeye salmon. Ecology 77:1151–1162.
- Bjornn, T.C. and D.W. Resier, Habitat Requirements of Salmonids in Streams, American 8. Fisheries Society Special Publication, 83-138, 83 (1991).
- Crozier, L. G., MD Scheuerell, and R. W. Zabel. 2011, Using Time Series Analysis to Characterize Evolutionary and Plastic Responses to Environmental Change: A Case Study of a Shift toward Earlier Migration Date in Sockeye Salmon. The American Naturalist. 178: 755-773.
- DART. 2011. Columbia River Data Access in Real Time (DART). http://www.cbr.washington.edu/dart/dart.html. Accessed March 2012.
