Changes in growth and diet of smallmouth bass following invasion of Lake Erie by the round goby

Upon invading the Great Lakes, the round goby (Neogobius melanostomus) was rapidly incorporated in the diet of native predators. The smallmouth bass (Micropterus dolomieu) is an abundant nearshore predator and readily consumes round goby; however, the effects of round goby on growth of smallmouth bass have not been examined for a wide range of smallmouth bass ages. We compared smallmouth bass diets from New York waters of Lake Erie before and after the invasion of round goby and analyzed 19 years (pre-round goby = 1993-1998; post-round goby = 2001-2013) of length-at-age data (ages 2-10) to investigate the effects of round goby on growth of smallmouth bass. Analysis of variance was used to test hypotheses about the effects of sex, age, and round goby presence on length-at-age of smallmouth bass, and von Bertalanffy models were used to identify changes in growth patterns. Crayfish (Decapoda spp.) were the most common prey of smallmouth bass prior to invasion of round goby (observed in 53.5% of diets). Round goby became the dominant prey of smallmouth bass after its invasion (observed in 73.3% of diets), and crayfish were only observed in 5.8% of diets in the post-round goby time period. Length-at-age increased following invasion of round goby and the greatest increases in length (11-15%) were observed for ages 2-4. The von Bertalanffy growth coefficient, K, increased for both male and female smallmouth bass. Results from this study demonstrate how aquatic invaders can rapidly change population characteristics of native predators.