Diet and trophic relationships of fishes from the nearshore of the Bay of Quinte and Kingston Basin, Lake Ontario

Few studies have assessed spatial and seasonal variation in diet and trophic position of fishes within large lakes. Two areas of north-eastern Lake Ontario - the Bay of Quinte and the Kingston Basin – provide contrasts in temperature, nutrients and depth while supporting similar littoral fish communities and therefore provide an excellent system to address this information gap. In Chapter 2, diet and trophic position of the Round Goby (Neogobius melanostomus) varied seasonally and spatially between these two habitats. Stable isotopes indicated that stomach contents over-estimated the contribution of mollusc-prey to the diet of Round Goby and under-estimated the contribution of soft-bodied prey. In Chapter 3, I investigated differences in food web structure in these two habitats, and observed a general increase in trophic positions in the Kingston Basin. Diet as revealed by stomach contents and stable isotopes, and relative contribution of terrestrial versus pelagic primary production to fish production differed between locations. Accounting for spatial, temporal and ontogenetic aspects of fish diet and food web structure can lead to a better understanding and management of ecosystem based differences within and among large lake ecosystems