The lake trout refuges in the Apostle Islands region of Lake Superior are analogous to the traditional concept of a marine protected area. These refuges closed to most forms of fishing have been implicated as one of several management actions leading to the successful rehabilitation of Lake Superior stocks of lake trout (Salvelinus namaycush). To further investigate the ecological significance of these two refuges on both target and non-target species, I analyzed fishery-independent survey data collected by the Wisconsin Department of Natural Resources since 1982 and evaluated trends in mean catch of lake trout, lake whitefish (Coregonus clupeaformis), and cisco (Coregonus artedi) sampled inside versus outside of refuge boundaries. I found that lake trout relative abundance was higher inside the refuges and also increased at a greater rate inside the refuges, where lake trout fishing was prohibited, than outside. The annual relative abundance of lake whitefish was higher in areas outside of the refuges. However, the rate of increase in lake whitefish relative abundance was greater inside refuge boundaries, which was indicative of a refuge effect. Analysis of relative abundance of cisco, a potential prey item of lake trout, did not demonstrate significant trends in either area. Overall, this study highlights the potential importance of the refuges for enhancing populations of species beyond only those that were the original target of the refuges, as demonstrated by the changing relative abundance of lake whitefish. Improved understanding of refuge effects on populations of Great Lakes fishes is therefore valuable to inform future fisheries management.
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