The Round Goby (Neogobius melanostomus) is one of the most recent invasive species to become established in Oneida Lake, and its impacts on young piscivores are still unclear. Round Goby invasions have had both positive and negative ecological impacts in other lakes because they increase food availability for piscivores while also competing with native prey-fish species. Growth and survival of young-of-year (YOY) piscivores in Oneida Lake are strongly correlated with the ir piscivory rates, so diet analysis is a useful tool for assessing the potential impacts of ecosystem changes. To determine the effect of gobies on bass, we examined the stomach contents and growth of YOY Largemouth Bass (Micropterus salmoides) and Smallmouth Bass (M. dolomieu) before and after the goby arrival. Archived bass specimens, originally collected using seines, trawls, or fyke nets, were assigned to a ‘pre-goby’ (2010-2013) or a ‘post-goby’ (2015-2017) group depending on the year of collection. Piscivory rate was calculated as the percentage of bass containing fish with respect to the total number of bass containing food. To investigate the goby’s impact on YOY Largemouth and Smallmouth Bass diets and growth rates, we compared the piscivory rates and mean lengths of pre- and post-goby bass.
In pre-goby samples, 95% of Largemouth and 53% of Smallmouth Bass contained fish; in post-goby samples, 87% of Largemouth and 47.5% of Smallmouth Bass contained fish. Mean bass lengths increased from pre- to post-goby datasets, from 93mm to 98mm (Largemouth) and 88mm to 109mm (Smallmouth). In 2015-2016, goby comprised 20% and 81% of identifiable fish consumed by Largemouth Bass and Smallmouth Bass, respectively. While there was no significant change in total piscivory rate, Smallmouth Bass showed a significant increase in growth rate after the Round Goby arrival (p =.013). Additionally, Largemouth Bass appear to begin eating fish earlier since the arrival of Round Goby. Increased piscivory by Largemouth and Smallmouth Bass may increase survival to adulthood, and thereby lead to higher catch rates and weights for recreational anglers. In conclusion, the Round Goby has recently become an important food source for YOY bass in Oneida Lake, leading to increased YOY growth and survival rates and potentially having a net positive impact on local bass populations.