Large-Scale Lake Michigan Round Goby Trophic Behavior Variability: Are There Seasonal, Spatial, Habitat-Based, and Depth-Related Differences?

Invasive species have dramatically restructured the Lake Michigan ecosystem over the past 100 years and will likely continue to disrupt this system well into the future. Understanding trophic interactions among native and non-native species is key to elucidating potential impacts of current and potential future invaders. Round Goby were first detected in Lake Michigan in 1994, and have since increased dramatically in abundance. While past studies of round goby in Lake Michigan have primarily focused on specific regions and habitats, Lake Michigan is a large, diverse system and round goby trophic interactions may vary across regions and over time. During 2010, we collected round goby and their potential prey at ten sites throughout Lake Michigan, including hard bottom and soft bottom habitats. At each site, gobies were collected during May, July, and September at three depths (3m, 7-9m, and 14-16m) via 2-hr bottom set, micromesh gillnets. In the laboratory, diet items were examined to the lowest taxonomic level and compared to available prey. Diet selectivity and multivariate analyses will be used to quantify diet content variability and relationships to environmental conditions (prey availability, substrate type, depth, and season). Results should provide a more holistic representation of the predatory effects of round goby throughout nearshore Lake Michigan.