Sockeye salmon bigger today than 100 years ago in B.C.

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Michael Price takes scales from a salmon sockeye in British Columbia.

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Century-year-old fish scales reveal that the annual growth of young sockeye salmon in freshwater lakes has increased by an average of 22% in recent years compared to a century ago, according to a study by Simon Fraser University and Fisheries and Oceans Canada.

Fish from deep, historically cold, relatively unproductive lakes grew the most, says Michael Price, lead author of the study and a postdoctoral researcher at Simon Fraser University.

Collected since 1913, the scales help determine the growth over time of young sockeye salmon in northern British Columbia. The study, published in December in the scientific journal Global Change Biology, focused on the 13 populations of the Skeena watershed.

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Analyzing sockeye salmon scales makes it possible to trace their growth over time.

When you look at a fish scale, it's like the trunk of a tree. It has concentric rings and can tell us the age of the fish, but also its growth for each of these years.

A quote from Michael Price, Simon Fraser University

This increased growth can be explained by warmer temperatures in winter according to the researcher: These freshwater lakes experience milder winters and therefore longer ice-free periods and longer growing seasons. long.

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The decline in salmon stocks also plays a role. There is a very significant decrease in the number of adult sockeye salmon returning to the Skeena watershed and throughout British Columbia, leading to a reduction in competition in these freshwater lakes, notes the researcher.

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Michael Price, a postdoctoral researcher at Simon Fraser University, is researching the growth of sockeye salmon over time. time in British Columbia.

Sockeye salmon grow in lakes for one to two years before migrating to the ocean. This habitat therefore has a considerable impact on fish. The bigger the salmon, the more likely they are to survive. So we think it's a positive thing, he said.

Salmon, however, are particularly sensitive to high temperatures. A watercourse that is too hot can be fatal. Thus, deeper lakes provide more suitable habitats, acting as temperature moderators.

The study indicates that for salmon to respond positively to climate change, they need a diverse set of habitats, notes Eric Taylor, a professor of zoology at the University of California. British Columbia who did not participate in the study. It is necessary to take into account all the watercourses and ecosystems that feed a lake.

Maintaining a Diversity of freshwater habitats would therefore promote the resilience of wild salmon to climate change.

We can control the habitat once they return to the rivers and lakes which we can protect and thus facilitate their adaptation to future changes, concludes researcher Michael Price.

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