Niches and trophic positions of top predator
fish species in the lower Huron-Erie Corridor
Brent Nawrocki
MSc. Candidate
GLIER, University of Windsor
Friday, March 21st, GLIER Conference Room, Rm 250
Top predators are indicators of ecosystem health and stability. Examining the niche
width and overlap between top predators is useful in evaluating how top predators co-exist and
if functional redundancy exists. The Great Lakes has a significant number of predatory fish yet
how these species co-exist and whether there is niche overlap between these species has
received little attention. Lake St. Clair and the Detroit River have a wide variety of predators
such as Longnose Gar (Lepisoteus osseus), Largemouth Bass (Micropterus salmoides) and
Walleye (Sander vitreus) that are integral to the established food web and provide a model
system for studying niche overlap in freshwater predators. The objective of this study is to
quantify niche width and overlap of top predators in the lower Huron-Erie Corridor using stable
isotopes of carbon (δ13C) and nitrogen (δ15N) in muscle and liver tissue, to determine the
influence of season, year and space on diet and carbon sources. Preliminary results indicate
that isotopic niche of top predators is influenced by both time of year and location. Isotopic
niches suggest that top predators have varying degrees of overlap and the potential to feed at a
range of trophic positions. The results of this research will more clearly define the ecological
role, the potential for niche overlap and competition, and whether functional redundancy of
top predators is relevant in the lower Huron-Erie Corridor.