Research by ecologists at the University of Toronto and Ontario’s Ministry of Natural Resources and Forestry shows strong evidence in a freshwater lake of “fishing down the food web” – the deliberate shift away from top predatory fish on the food chain to smaller species closer to the base.
While the effect has historically been observed almost exclusively in marine ecosystems and ocean fisheries, there has been little evidence of the effect in freshwater ecosystems.
A study published this month in Proceedings of the National Academy of Sciences reports a significant difference in harvests from Lake Simcoe, a large inland lake less than 100 kilometres north of Toronto, between two distinct periods over nearly 150 years. They found evidence of the effect of fishing down the food web during years of commercial fishing in the century leading up to the 1960s, followed by a reversing trend of fishing up the food web in the 50-plus years since commercial fishing operations ceased and recreational fishing increased.
“The early commercial activity that occurred from the mid-1800s to the early 1900s resulted in the depletion of some of the large, iconic predators in the lake such as lake sturgeon, muskellunge and walleye,” said Don Jackson, a professor in the department of ecology and evolutionary biology in the Faculty of Arts & Science at U of T and a co-author of the study.
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