The presence of round gobies (Neogobius melanostomus) in Oneida Lake, NY, has had widespread effects on other species. Benthic macroinvertebrates have important intermediate positions in aquatic food webs and influence the entire ecosystem. The arrival of dreissenids (zebra mussels in 1992 and quagga mussels in 2006) to North American lakes increased benthic invertebrate abundance along with water clarity, allowing more production on the lake bottom and more efficient foraging by fish. In 2014, round gobies invaded Oneida Lake; the fish are known predators of mussels and also feed on amphipods, chironomids, and fish eggs. A long-term data set on benthic macroinvertebrate populations begun in 1960 was compared to measurements of round goby abundance. Long-term data were collected at three sites in the lake with Ekman grabs every second week. Further benthos samples were collected between June 22 and July 12, 2017, at 38 sites of varying depths and substrates. Three Ekman grabs were taken at each site, and all benthic macroinvertebrates of interest were identified and counted. Mussel lengths were measured using ImageJ. Goby abundance at the same sites was estimated with an underwater video camera for comparison.
Results/Conclusions
By 2015, the round goby was the dominant benthic fish species in Oneida Lake. Long-term data show a decline in all benthic invertebrate groups, including mussels, after the arrival of round gobies. On the local scale, total abundance of benthic macroinvertebrates was negatively correlated with round goby densities, but only when excluding zebra and quagga mussels, the latter of which were far more prevalent in benthos samples than the former. No relationship was found between goby density and mussel length, but there was a positive relationship between goby density and mussel area coverage of the lake floor. These results indicate that gobies may be attracted to areas with higher mussel density and thereby contribute to declines in other macroinvertebrates in those areas. When considering only sites without gobies, total benthic abundance increased as site depth decreased, as benthic macroinvertebrates favor shallow, sandy and rocky substrates. Knowledge of how benthic communities have changed over time and in local sites after the introduction and proliferation of round gobies is essential to understanding the lake’s ecosystem’s response to this invasive species.