Date of Award


Publication Type

Master Thesis

Degree Name



Earth and Environmental Sciences

First Advisor

Fisk, Aaron

Second Advisor

Johnson, Timothy


diet, forage fish, Lake Ontario, niche, salmonid, stable isotopes




Lake Ontario supports a diverse offshore fish community consisting of salmonids and forage fish with little known about the resource partitioning and habitat use of these species. To assess this, I used stable isotopes to determine the isotopic trends (forage fishes only), niche structure and overlap of both salmonids and forage fishes. I also estimated the salmonid trophic position (TP) and diet using stable isotopes. Forage fishes had high resource partitioning but was low between Myoxocephalus thompsonii and Cottus cognatus. Regional and temporal discrete subpopulations driven largely by nitrogen were only present in Alosa pseudoharengus, Osmerus mordax and Neogobius melanostomus. Salmonids had low resource partitioning, particularly Oncorhynchus tshawytscha and inhabit the offshore. A. pseudoharengus comprised a major proportion of the salmonid diet, followed by N. melanostomus while Salvelinus namaycush had the highest TP. Salmo salar restoration may prove difficult to due to high isotopic and diet overlap with other salmonids.