Seasonal abundance, diet, and energy consumption of round gobies (Neogobius melanostomus) in Lake Erie tributary streams

The invasive round goby (Neogobius melanostomus) is a benthic invertivore that has become established in many lake and river systems of Europe and the United States, especially within the Great Lakes basin. Multiple reports document its negative impact on benthic macroinvertebrates and fishes in lakes and recent studies show fish and invertebrate communities in streams are equally at risk. We assessed the seasonal abundance of round gobies and their summer diet composition in tributary streams to Lake Erie. Populations of round gobies in the lower reaches of two tributary streams peaked in abundance in early fall, were absent in late winter, and reappeared in early spring, suggesting a possible out-migration to the lake in winter. Population size distributions show a peak recruitment of young round gobies in July and low-level recruitment through October. In this study, round gobies obtained most of their energy from amphipods, chironomids, and caddisflies compared to other invertebrates, and midges were consumed in greater proportion than their availability suggesting a preference for these prey. As the stream lacked molluscs, large round gobies remained generalist invertivores without a diet shift to molluscivory as has been reported in lake studies. The observations on recruitment and abundance, and possible out-migration suggest the lower reaches of tributary streams may act as source populations for lake-bound round gobies. It may be possible to take advantage of this out-migration behaviour as a control strategy to capture large numbers of round gobies each winter.