Prey choice among piscivorous juvenile walleyes
In order to examine prey selection by walleyes (Stizostedion vitreum), I compared prey electivities for walleyes in Sparkling Lake, Wisconsin, with the results of species-preference experiments in the laboratory. Before young-of-the-year (YOY) yellow perch (Perca flavescens) were present in the littoral zone of Sparkling Lake, juvenile walleyes fed significantly less on minnows and more on darters than expected based on the relative abundance of these two taxa in the lake. After large numbers of YOY yellow perch appeared in the littoral zone, walleyes fed primarily on the abundant yellow perch, although their diet was not significantly different from that predicted based on the relative abundance of minnows, darters, and YOY yellow perch in the lake. In laboratory experiments, juvenile walleyes ate more bluntnose minnows (Pimephales notatus) than YOY yellow perch, and almost never ate johnny darters (Etheostoma nigrum). Walleyes were more successful at capturing bluntnose minnows than YOY yellow perch, but even when this was taken into account, walleyes ate more bluntnose minnows and fewer YOY yellow perch than expected, indicating that walleyes preferred bluntnose minnows to YOY yellow perch. Differences in prey selection between walleyes in the field and in the laboratory may have been related to differences among prey in distribution and movement patterns in Sparkling Lake.