Impact of Lake Size on Largemouth Bass Diet Diversity

As lake size increases, habitat heterogeneity and prey refugia increase, diversifying species assemblages, and increasing food chain length.  More prey species in large lakes may increase diversity of predator diets.  Alternatively, increases in system size may support larger populations of optimal prey, thereby reducing the diversity of predator diets.  We sampled largemouth bass (LMB) diets from three unexploited lakes of varying size (25.8 – 1.5 ha) in Michigan’s Upper Peninsula to understand how lake size affected apex predator diets.  We found that as lake size increased; diet diversity decreased (ranged from 0.78 – 0.15), mean number of prey taxa decreased (4.1 – 1.1) and the mean number of prey items decreased (80.5 – 5.72).  Additionally, we found that diets containing only fish prey were greater in the larger lakes (>45%) than in smaller lakes (<27%), the percent of empty stomachs also increased in the larger lakes (25 – 2%).  Our hypothesis asserts LMB narrow diet niche in larger lakes compared to bass in smaller lakes. In larger lake systems LMB show an increase in trophic optimization by consuming higher proportions of energetically valuable fish prey.