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Ecological Impacts of Introduced Rainbow Darters (Etheostoma caeruleum) in the Mohawk River Watershed

The Rainbow Darter (Etheostoma caeruleum) is a small, brightly colored, bottom-dwelling fish that is native to the Lake Erie, western Lake Ontario, and Allegheny River watersheds in western New York. In 2009, this species was discovered in Fox Creek, a tributary of Schoharie Creek, in the Mohawk River watershed, but was not known from other sites in the basin. In 2013, during routine surveys in the area, we discovered Rainbow Darters in the Switzkill, which is a tributary of Fox Creek, but also in the Plotter Kill, a tributary of the main stem Mohawk River, indicating possible dispersal and range expansion through Schoharie Creek and the Mohawk River. In 2014, we began broad scale surveys of the Schoharie Creek and eastern Mohawk basins and have documented Rainbow Darters at 10 additional sites throughout these drainages, often at very high population densities, indicating that the species has become established in these parts of the watershed. Surveys continue to document the full extent of this species’ colonization and expansion in the Mohawk watershed, along with examinations of past museum collections from these sites. The specimens contained in these museum collections, when compared to more recent survey results, will help to identify other species that may have decreased in abundance since this darter’s introduction. We are complementing these surveys and historical examinations with dietary studies, in order to identify those species that show overlap with the Rainbow Darter and which may have been, or continue to be, negatively affected by this introduced species.