Abstract

Habitat coupling describes material exchange either between adjacent systems or between habitats within an aquatic system, and can be important to consumer populations by supplementing or providing alternate prey resources. We studied four embayments along the southeastern shore of Lake Ontario to explore if differences in habitat coupling were correlated to differences in population characteristics among dominant fish species. Embayments differed in morphometry, watershed characteristics, and connectivity to Lake Ontario. Two embayments were dominated by pelagic habitat and two were dominated by densely vegetated, littoral habitat. Embayment fish populations differed in abundance, biomass, and size structure. We assessed habitat coupling using fish diets and 15N and 13C stable isotope ratios. 13C isotope data suggest fish food webs in the pelagic-dominated embayments incorporated a greater amount of energy from planktonic sources. In contrast, food webs in littoral-dominated embayments may depend on a wider variety of energy sources, including benthic algae and inputs from adjacent habitats. Watershed nutrient inputs were positively correlated to fish biomass and abundance. Understanding the role of habitat coupling in embayment fish community dynamics is important to managing these systems at the watershed scale.