Expanding from Marine to Freshwater Protected Area Assessments: A Case Study Evaluation of Lake Trout Refuges in Lake Superior

Various tools exist for the management of habitats and associated resources in marine and freshwater ecosystems.  The implementation of marine protected areas (or aquatic protected areas in systems that include freshwater) is one such approach that has been gaining both worldwide and national attention in recent decades.  Aquatic protected areas (APAs) were established for various ecological and socio-cultural purposes in the Great Lakes, including facilitation of lake trout (Salvelinus namaycush) rehabilitation through creation of refuges protected from fishing mortality.  The existence of these APAs provides an opportunity to evaluate whether the potential benefits of marine reserves on fish populations are comparable in this particular freshwater environment.  Understanding these refuges’ effects is an important part of evaluating their role in management of native Great Lakes fishes, especially in the face of the inherent controversy associated with the restrictions to resource use.  To further investigate the ecological significance of two Lake Superior refuges on both target and non-target species, we analyzed fishery-independent survey data collected by the Wisconsin Department of Natural Resources since 1982 to compare trends in relative abundance of fishes sampled inside versus outside these refuges.  In addition to lake trout, the target species, we evaluated trends in mean relative abundances of lake whitefish (Coregonus clupeaformis) and cisco (Coregonus artedi).  Lake trout relative abundance was higher inside the refuges and also increased at a greater rate inside the refuges as compared to areas outside the refuges.  Annual means in lake whitefish catch were higher in areas outside of the refuges; however, the rate of increase in relative abundance was greater inside refuge boundaries and was indicative of a refuge effect.  Analysis of relative abundance of cisco, a prey item of lake trout, did not demonstrate significant trends in either refuge or non-refuge areas.  Overall, this study highlights the potential importance of the refuges for enhancing fish populations beyond those that were the original target of the refuges, as demonstrated by the increasing relative abundance of lake whitefish inside the refuges.