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There's a long-standing belief in the freshwater fishing community that once anglers find it too hard to land a particular fish for their dinner plate, they either move on to fishing for different species or fish in new waters, giving depleted populations time to rebound.
But this "self-regulation" assumption, says University of Wisconsin-Madison Center for Limnology graduate student Holly Embke, turns out to be wrong. Embke is lead author of a study published this week [Nov. 18, 2019] in the Proceedings of the National Academy of Sciences that shows when stocks of fish get so low that it becomes a greater challenge to catch them, many anglers step up to the challenge and continue catching fish. This poses a threat to the long-term health of sportfish populations in Wisconsin and in inland recreational fisheries around the world.
Study - Stocks - Game - Walleye - Lakes
The study examined stocks of the popular game fish walleye in 179 lakes in Wisconsin and found that 40 percent of walleye populations are overharvested, says Embke. By assessing fish stocks with the currently accepted models that minimize angler impacts, she and her co-authors say, resource managers miss this "hidden overharvest."
Over the last few decades, walleye populations in Wisconsin have dramatically declined because of climate change. They are a cold-water species that thrive in cooler conditions, but as lakes in the upper Midwest warm, says co-author Steve Carpenter, director emeritus of the Center for Limnology, they offer less cold-water habitat for walleye.
Walleye - Production - State - Lakes - Percent
Annual walleye production across the state's more-than 900 "walleye lakes" has declined by 35 percent over the last 30 years. On top of that, walleye stocks now take one and a half times longer to grow than they did in 1990.
However, despite climate-driven decline, walleye are as popular as ever among anglers and the annual percentage of walleye that they are permitted to harvest...
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