Date of Award


Publication Type

Master Thesis

Degree Name



Earth and Environmental Sciences


Timothy Johnson


Health and environmental sciences, Biological sciences




My research was designed to evaluate predator-prey relationships in Lake Erie and the effects of watersheds, through river inputs, on prey consumption. I analyzed stomach contents of fishes collected from two distinct river plumes in Lake Erie's western basin to see if elevated turbidity in one river plume reduced predation mortality of larval fishes. I found that quantifying larval fish predation mortality is a difficult task; only 16 of 3,467 stomachs analyzed contained larval prey. I used laboratory experiments to evaluate digestion rates of larval fishes and found that both the complete breakdown of larvae in predator stomachs and the loss of morphological characters needed to identify larvae occurred rapidly, suggesting that conventional diet analyses are inadequate for quantifying larval predation mortality. My diet analyses did reveal spatial and temporal differences in prey consumption between river plumes, which are likely being driven by bottom-up and top-down effects associated with inputs of nutrients and sediments from tributary streams. Collectively, my results will allow managers to quantify the likelihood of detecting larval fishes during stomach content analyses and to better understand how tributary inputs influence predator-prey interactions.