Walleye are an iconic sport fish species throughout North America. In Wisconsin, walleye populations have declined since the 1980’s, leading to substantial investment in walleye rehabilitation efforts. However, the ultimate causes of walleye declines are uncertain. Concurrent increases in black bass populations have raised questions regarding direct interactions between bass and walleye, as well as the relative responses of each species to changing environmental conditions.
In this webinar, we describe the status of ongoing research examining trends in Wisconsin’s sport fish communities and drivers of those trends. Although walleye populations and recruitment have declined in most lakes, some populations have remained stable and others have increased, suggesting that the relative importance of various drivers differs among lakes. We developed a regional model of lake temperatures used to identify thermal characteristics of lakes associated with fish community changes.
Walleye recruitment success was highest in lakes that accumulated fewer degree days and in large lakes. Field studies on several Wisconsin lakes demonstrated that direct consumption of walleye by largemouth bass is rare, although their diets exhibit substantial overlap. Currently, the Wisconsin Department of Natural Resources is embarking upon an adaptive management experiment to determine if declines in walleye recruitment can be offset by stocking, decreased walleye harvest, and increased bass harvest.
Our research on fish community changes in Wisconsin is relevant to managers and researchers interested in how environmental change may influence lake communities, and how management responses can be most effective.
This work was supported by the USGS National Climate Change and Wildlife Science Center.