The Role of Compensatory Dynamics and Multi-Scale Environmental Factors in Structuring Fish Populations in Indiana Glacial Lakes

Fish populations are structured by a combination of environmental variables, productivity of lower trophic levels and within system compensatory interactions (e.g., predation and competition).  The relative influences of these different factors can have important implications for targeting management actions to affect fish populations (e.g., abundance, growth, condition), but the relative influences of diverse processes are largely unknown. Glacial lakes in Indiana differ from many other North American glacial lakes in that they are located in lower latitudes and agriculturally-dominated landscape, and hence are characterized by warmer temperatures and eutrophic conditions. We evaluated the relative roles of in-lake factors, lakeshed characteristics, landscape variables and compensatory interactions in structuring population characteristics of 11 fish species in Indiana’s glacial lakes. We partnered with the Midwest Glacial Lakes Fish Habitat Partnership to delineate lakesheds for glacial lakes in Indiana, and we obtained information on fish populations (relative abundances, growth, condition) from long-term, standardized monitoring performed by the Indiana DNR.  Our results suggest that compensatory interactions have relatively minor influence in affecting across-lake patterns of fish populations.  While environmental factors collectively have stronger influence, the effect of specific environmental factors and the spatial scale of influence were inconsistent across fish species and population metrics.