Spatial and temporal dynamics of nearshore fish communities in Lake Michigan and Lake Huron

Ecosystem changes across the Great Lakes have increased the importance of understanding the role of nearshore zones (< 30 m depth) in lake-wide dynamics. We evaluated spatiotemporal dynamics of nearshore fish communities in the Michigan waters of the Great Lakes, focusing on Lakes Huron and Michigan, using multiple long-term gill net surveys. We assessed temporal dynamics of nearshore fish community composition, metrics of species diversity, and catch-per-unit-effort (CPUE) of key fish species across fifteen nearshore areas in exposed coastlines and coastal embayments. Permutation multivariate analyses of variance demonstrated significant differences in the composition of fish communities between sites. Canonical correspondence analyses indicated this was driven by differences between exposed coastlines and coastal embayments, which differed in productivity, depth, temperature, and the relative composition of fish from thermal and eutrophication tolerance guilds. Dissimilarities of fish communities among locations were primarily driven by differences in the relative abundance of a few numerous, ubiquitous species that represent only a small subset of total species richness. Analyses of diversity profiles via Hill numbers indicated that species composition was unevenly distributed within nearshore fish communities and was dominated by approximately five species within a location. Warm- and cool-water species richness generally increased over time. While CPUE of most species decreased, some top predators increased at some locations. These results highlight that local environmental conditions, such as temperature and productivity, drive nearshore fish community heterogeneity, requiring that researchers and managers use caution when extrapolating local trends to the wider range of environmental conditions found at broader scales.