Habitat influences on juvenile largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) distributions, diets and movement strategies in lentic systems

Glacial lakes in the northern portion of the Midwest United States are complex ecosystems with several distinct habitat types. Littoral habitat features provide important refuge and forage area for juvenile fish, and thereby may impact distributions, growth and diet selection of young fish. Simultaneously, lake-scale habitat features may structure overall system productivity and affect various population metrics of juvenile fish. Due to the interaction among lake-scale and local nearshore habitat features, it is difficult to interpret which scale and which particular habitat features most strongly influence population metrics of young fish. We conducted a field study exploring the influence of both nearshore and lake-scale habitat features on juvenile largemouth bass (Micropterus salmoides) and bluegill ( Lepomis macrochirus) population metrics. We further examined mechanisms structuring habitat selection in juveniles of these species by developing and applying an individual-based eco-genetic model. We documented that local nearshore habitat features most strongly influence distributions of both species, while lake-scale variables most strongly influence size structure. Size of juvenile largemouth bass strongly influenced diet of this species, but nearshore scale habitat variables also influenced diet metrics of juvenile largemouth bass. Finally, simulation results indicate that juvenile largemouth bass and bluegill select habitat differentially and that vegetation characteristics could influence how juvenile fish select habitat. We suggest that our utilization of two very different strategies to describe juvenile fish populations provides a unique perspective on dynamics of these two species.