Ecological tracers reveal resource convergence among Lake Ontario prey fishes

Session: 54. - Food Web Ecology and Dynamics of Lake Ontario: Nearshore ? Pelagic Linkages

Gordon Paterson, Michigan Technological University, gpaterso@mtu.edu
Scott Rush, Dept. of Wildlife, Fisheries and Aquaculture, Mississippi State University, srush@cfr.msstate.edu
Michael Arts, Ryerson University, michael.arts@ryerson.ca
Ken Drouillard, University of Windsor, Great Lakes Institute for Environmental Research, kgd@uwindsor.ca
G. Doug Haffner, Great Lakes Institute, Univ. of Windsor, haffner@uwindsor.ca
Timothy Johnson, Ontario MNRF, Glenora Fisheries Station, tim.johnson@ontario.ca
Brian Lantry, U.S.G.S., Lake Ontario Bio Station, bflantry@usgs.gov
Craig Hebert, Environment and Climate Change Canada, craig.hebert@ec.gc.ca
Daryl McGoldrick, Environment and Climate Change Canada, daryl.mcgoldrick@canada.ca
Sean Backus, Environment and Climate Change Canada - Water Quality Monitoring and Surveillance Division, Sean.Backus@canada.ca
Aaron Fisk, University of Windsor, afisk@uwindsor.ca

Abstract

This study measured stable carbon (?¹³C) and nitrogen (?¹⁵N) isotopes and fatty acids in Lake Ontario alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), slimy sculpin (Cottus cognatus) and round goby (Neogobius melanostomus) collected from 1982 to 2008 to investigate how temporal variability in these ecological tracers can relate to ecosystem-level changes associated with the establishment of dreissenid mussels. Prey fish d15N values remained relatively constant, with only slimy sculpin exhibiting a temporal increase in d15N. In contrast, d13C values for alewife, rainbow smelt and, especially, slimy sculpin became less negative over time and were consistent with the benthification of the Lake Ontario food web associated with dreissenids. Temporal declines in fatty acid unsaturation indices and ?n-3/?n-6 ratios, and also increased 24:0/14:0 ratios for alewife, rainbow smelt and slimy sculpin, indicated the increasing importance of nearshore production pathways for more recently collected fish and resulted in values more similar to those for round goby. These results indicate a temporal convergence of the food niche , whereas food partitioning has historically supported the coexistence of prey fish species in Lake Ontario. This convergence is consistent with changes in food-web processes associated with the invasion of dreissenid mussels.

1. Keyword
stable isotopes

2. Keyword
fish

3. Keyword
Dreissena

4. Additional Keyword
fatty acid

5. Additional Keyword
niche