Fish Out of Water

The walleye (also known as pickerel) is one of Ontario’s most popular recreational and commercial fish. Now it may be at risk of ­disappearing because of predatory and invasive smallmouth bass moving into Ontario lakes, a recent York study has found.

Climate change is warming Ontario’s lake waters. Walleye populations are declining as a result, because of reduced suitable habitat and competition from invading smallmouth bass. These findings, by biology Professor Sapna Sharma’s recent master’s student Thomas Van Zuiden, have large implications.

“Walleye play an important role in lake ecosystem dynamics as top predators, and are also a popular angling target for commercial and recreational fisheries,” says Van Zuiden.

Van Zuiden and Sharma analyzed data from 722 Ontario lakes and found that when walleye and smallmouth bass are living in the same lakes there are three times fewer walleye. The York researchers predict that the co-occurrence of the two fish species may increase as much as 332 per cent by 2070, ­significantly increasing the vulnerability of walleye populations across the province.

“The future is looking dim for walleye in Ontario,” says Sharma. “Our study illustrates the importance of including multiple environmental stressors in statistical models when attempting to understand changes in biodiversity.”