Climate change to blame for receding sockeye salmon

By Janine Weber 0705945

Sockeye salmon in the Fraser River, British Columbia, are very important economically to Canada. The fishery is the highest grossing fishery in all of Canada, and it also is significant to Aboriginal peoples who rely on these fish for food and for spiritual ceremonies. Most sockeye spend about half their lives just south of the Aleutian Islands in the open ocean, where they develop their characteristic rich flavour and bright orangey-red flesh. After four years, most sockeye return to their rivers to spawn. Climate change, along with overfishing and disease, causes a hazard to these valuable fish as it changes their habitat and temperature of the water. Fraser River sockeye salmon populations increased vividly at the end of the 1970s and then dropped in 1995 as oceanic conditions changed. These salmon leave the salty ocean and enter freshwater rivers and lakes where they reproduce, and the increasing freshwater temperatures pose as a risk for future salmon generations. All populations are experiencing warmer river temperatures than ever before, the Late-runs encountering temperatures 3-6° C warmer. The Late-runs have begun entering the Fraser River 2-6 weeks earlier than usual, with indication that the ocean’s changing environment is to blame. 50-95% of these Late-runs migrating early die before they get the chance to reproduce, because of high water temperatures. Other runs of fish in the Fraser River are dying due to the raising temperatures as well. No sockeye salmon anywhere in the world have been observed to carry-out migration at 20°C, but Fraser River salmon are now facing temperatures greater than 19° C. Not just water temperatures are effected by climate change, but also precipitation patterns, the speed of the river (which will increase in winter and spring), and altered runoff patterns. The altered runoffs will cause the river to have less nutrients, which means food will be made inaccessible to undeveloped fish. Adult fish will also have trouble finding food, as air pressure gradients will result in a reduction of surface wind and a 5-9% decline of zooplankton. A workshop was recently held to assess vulnerability of sockeye salmon at different temperatures and locations. Interviews with scientific specialists established that vulnerability judgments could be made by observing sockeye salmon throughout their life cycle. Next, a thorough background paper was made collecting all scientific knowledge about climate change and sockeye salmon. A survey was then prepared and given to 13 knowledgeable people on the subject, such as fishery specialists. The experts first rated from 1-5 the vulnerability of the salmon at each life stage at air temperatures 2° C and 4° C higher than average at 3 different parts of the river (upper, middle, and lower). Next they rated the effects of 2° C and 4° C increased temperature over a 60-year time frame (15 cycles of sockeye salmon). The tests examined the effects of changing the location and temperature of the water on overall vulnerability. The surveys were then collected in a database and reviewed. There was definite agreement that fish were most vulnerable in the middle section of the Fraser at an increase in 4° C normal temperatures, and in the upper section of the river at 4° C above normal temperatures. Eggs as well as returning adults after spawning were found to be the periods of the cycle most vulnerable to climate changes. The average vulnerability rating of eggs was 3.67/5 and returning adults was 3.82/5 for all temperatures and regions of the river. It was settled that the most important part of the sockeye’s life cycle was the adult fish reaching the spawning spot, as it is vital to all the other stages. At the end of the workshop an idea to construct new spawning channels to assist the eggs to help maintain sockeye populations was brought up. Not a lot of other solutions are available to help the situation, for example it wouldn’t be plausible to add cool water to the river as ridiculously large amounts would be needed. The good news is the Fraser River sockeye salmon have already shown to be capable of adapting to new environmental conditions. Hopefully the rate the climate is changing will slow down and not have a dramatic effect on future salmon populations.

Reference list:

McDaniels, Tim, Sarah Wilmot, Michael Healey, and Scott Hinch. "Vulerability of Fraser River Salmon to Climate Change: A Life Cycle Perspective Using Expert Judgements." Journal of Environmental Management 91.12 (2010): 2771-780. Web.


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