Spatial patterns in dry weight of nearshore Lake Michigan prey fishes

Abstract

The ability for individuals to adapt to local food sources likely allows for regional persistence of aquatic populations. In the Laurentian Great Lakes, invasive species and changing physical conditions have vastly altered local and regional food webs, leading to the potential for variation in energy flow up to large predators. To assess the potential that prey fish condition varies spatially, we examined patterns in proportion dry weight of prey fishes collected from Lake Michigan nearshore areas (<16 m) in 2010 and 2011. Absolute pairwise differences in dry weight of fishes were as high as 9% between some of our sampling sites, but sites exhibiting relatively high or low values were patchily spread across the lake. The range of proportion dry weight values observed in our study do encompass previously-reported mean values; however, the values reported in our study are slightly lower than those previously reported for Lake Michigan. In contrast to previous studies, our analyses do not suggest that variation in prey fish condition exhibits a consistent spatial pattern around nearshore Lake Michigan, and high within-site variation of prey fish condition prevents strong conclusions about specific sites providing generally more (or less) energy-rich prey to predators.