Walleye Foraging Ecology in an Interconnected Chain of Lakes Influenced By Non-Native Species

The introduction of non-native species into the Great Lakes has altered the forage ecology and population demographics of native predators.  The Great Lakes are a source of non-natives species for inland lakes throughout the region; however, there has been little study of the foraging ecology of predators in smaller systems invaded by non-native species. We used diet and stable isotope analysis to describe the contribution of native and non-native forage species to Walleye (Sander vitreus) within a lake chain invaded by multiple non-native species. Our a priori hypothesis was that Walleye diet would be linked to the relative amount of prey in open-water habitats and to the dominant habitat type. We found that Walleye in smaller lakes exhibited flexibility in their response to non-native prey species. Similar to predators in the Great Lakes, Walleye in our study integrated littoral non-native species into their diet. However, Walleye unexpectedly showed limited usage of accessible non-native pelagic forage. We suggest that predator response to species introductions is likely context dependent, and warrants further investigation for multiple systems and predators to determine the full extent of how non-native species are integrated into the food web and their influence on native populations.