Distribution of Round Gobies in Coastal Areas of Lake Michigan: Are Wetlands Resistant to Invasion?

Abstract

Great Lakes coastal wetlands may be more resistant to invasion by certain nonindigenous species and thus serve as refuge habitats for native species. As a first step in testing this hypothesis, we investigated the distribution of round goby ( Apollonia melanostomus, formerly Neogobius melanostomus) in the lower reaches of several Lake Michigan tributary systems that contain both wetland and lake habitats near their confluences with Lake Michigan. Using fyke nets, we sampled round gobies in lake and adjacent wetland habitats in four systems in 2004 and six systems in 2005. In each macrohabitat (lake or wetland), we sampled three microhabitats (mono-dominant stands of Nuphar, beds of submersed aquatic vegetation, and bare sediment). We found that round goby catch was generally lower in wetland macrohabitats than adjacent lake macrohabitats and that round gobies appeared to prefer beds of submersed aquatic vegetation in lakes among the three microhabitats. The majority of round gobies in all habitats were relatively small (< 7 cm standard length). We also found a significant negative correlation between round goby catch and distance of sampling points from the Lake Michigan shoreline in 2005, suggesting that 1) Lake Michigan nearshore waters (including the connecting navigation channels and pier areas) may be serving as round goby spawning and nursery habitats with subsequent dispersal into the tributary lake/wetland complexes, and 2) round gobies may still be invading these systems from Lake Michigan. Our results provide evidence that coastal wetland habitats are more resistant to invasion by round gobies than adjacent lake habitats.