Goodbye salmon, hello tuna?

(Karen Barry)

Pacific salmon live in cool ocean waters. Southern British Columbia is near the southern limit of their range. Warming of the North Pacific could force salmon northward, reducing their numbers in rivers in southern British Columbia. Warm-water fish, such as tuna and mackerel, may take their place.

Warmer rivers stress salmon

Southern limit of sockeye salmon (Source: Burghner, 1991)

A warmer climate also poses problems for salmon as they move upriver to spawn. Salmon stop eating and rely on stored fat when they enter fresh water for the swim upstream. Salmon are cold-blooded - their metabolism is tied to the temperature of the surrounding water. If the water is too warm, salmon use up their energy stores and are unable to reach their spawning grounds. Warmer waters also increase the risk of bacterial and fungal infections in salmon.

Did you know?
Mackerel, a warm-water fish species, has been found in recent years in the waters off Vancouver Island. There is concern that mackerel may eat young salmon, further depleting stocks.

What can be done to ensure that salmon continue to survive in our rivers?

What impact would fewer salmon returning to spawn in the Fraser River and its tributaries have on the economy of British Columbia?

References

Burghner, R.L., 1991: Life history of sockeye salmon; in Pacific Salmon Life Histories, University of British Columbia, p. 3-117