Online

Block, Benjamin David

Biology

2020

M.S.

The seasonal energy dynamics of temperate fishes will likely be affected by climate change, especially during the winter. To date, freshwater fish are understudied in winter compared to other aquatic organisms, and additional winter-focused studies are urgently needed. Recent research has demonstrated that some fish species are more active in winter than previously thought, therefore, an inquiry into the energetic contributions of winter foraging to the annual growth of freshwater fishes is needed prior to imminent changes in winter conditions. Here I have empirically shown that winter foraging behavior and seasonal energy dynamics likely depend on the thermal preference of individual fish species. I compared the seasonal energy dynamics of the cool-water species yellow perch (Perca flavescens) to two warm-water species, pumpkinseed (Lepomis gibbosus) and bluegill (Lepomis macrochirus). Our results support our first hypothesis that cool-water species should forage in all seasons whereas warm-water species forage in the open-water seasons but exhibit reduced foraging in the winter. Our results also support our second hypothesis that winter foraging provides sufficient energy for overwinter growth in cool-water species but does not provide sufficient energy for overwinter growth in warm-water species. The relationships between winter foraging and seasonal energy dynamics of these fishes will likely be altered due to climate change. Decreased ice cover duration and increases in water temperatures and ambient light will likely affect the seasonal energy dynamics that these species have evolved to tolerate winter conditions in temperate lakes. Thus, changes to the seasonal energy dynamics of fishes would not only affect individual survival and reproductive success but also the transfer of energy through food webs, and recreational and commercial fisheries.