Survival of endangered salmon

Posted on May 26, 2009

The sockeye salmon of Snake River, Idaho, are notable because they have the most southerly distribution of all sockeye populations.  They also travel the largest distance from the ocean (1450 km) and ascend higher (2000 m) than other sockeye on their spawning migration.  However, Snake Riversockeye suffer a high mortality rate on their long migration, and the population is presently poised on the brink of extinction.  Until recently, almost nothing was known about the factors that affect migration mortality, but a telemetry study has revealed that survival is related to fish condition (which is in turn affected by the burden of parasites and injuries), the exposure to temperatures above 21oC (which increases metabolic costs and the prevalence of disease), and the timing and difficulty of migration.  Late-season migrants have a lower survival, and warming as a result of climate change is likely to further select against later migrants and increase the importance of cool-water habitat refuges.

Reference: Keefer, M. L.; Peery, C. A. & Heinrich, M. J. 2008Temperature-mediated en route migration mortality and travel rates of endangered Snake River sockeye salmon.  Ecology of Freshwater Fish, 17, 136-145.