Environmental Trends 2002

Climate Change

What is the Relationship Between Climate and Migration Success of Sockeye Salmon?

Average Fraser River Temperature (1953-1988)

SOURCE: Historical temperature data from the Pacific Salmon Commission, 1941-1998. Historical weather data from Meteorological Service of Canada, Environment Canada 1953-1998. Analysis by John Morrison, Institute of Ocean Sciences, 2001 for the Ministry of Water, Land and Air Protection. NOTES: Results are statistically significant at the 95 percent level.

Effects of Warm Water Temperatures on Sockeye Salmon

SOURCE: Graphic from Temperature Rising: Climate Change in Southwestern British Columbia. 1999. Poster.

What is the relationship between climate and migration success of sockeye salmon?

• The average summer temperature of the Fraser River increased by 1.1°C between 1953 and 1998. This warming trend appears to be largely due to changes in local climate, including increasing air temperature, during the same time period.

• The Fraser River supports important salmon runs. Every year, Sockeye migrate upriver to spawn at more than 150 sites in the river system.

• In several recent years, en route mortality for some Fraser River Sockeye runs was greater than 50%. Sockeye migrate in the summer when water temperature is the warmest but prefer colder water temperatures than other salmon species and may therefore be the salmon species most sensitive to climate change.

• Exposure to warmer water can speed up metabolic processes, creating stress in migrating fish. Fish may die from exhaustion or infection or they may reach the spawning grounds but be unable to spawn.

For detailed information, including graph data, see In-Depth report.