The relative abundance of Neogobius melanostomus (Round Goby) in the Pennsylvanian waters of Lake Erie, has increased dramatically since 1996. Associated with this increase, all benthic species in the main portion of the lake, except Percopsis omiscomaycus (Trout-perch), decreased in occurrence or were extirpated. Proterorhinus semilunaris (Tubenose Goby), which has established a reproducing population in Presque Isle Bay, Lake Erie, coexists with the Round Goby and Etheostoma exile (Iowa Darter), a candidate species for rarity listing by the Pennsylvania Fish and Boat Commission. Conversely, the decline in potadromous populations of Percina caprodes (Logperch) may be exacerbated by direct competition in the lake, and the presence of Round Gobies in the breeding grounds of tributaries (e.g., Twentymile Creek). In Elk Creek, the presence of Round Goby is associated with dietary shifts of Etheostoma caeruleum (Rainbow Darter), although Rainbow Darters co-exist with the Round Goby. The Round Goby has established a reproducing population in LeBoef Creek, a tributary of French Creek (Allegheny River), and we documented its presence in the main channel of French Creek. We suggest that natural barriers (e.g., waterfalls) may prevent the upstream migration of gobies. Furthermore, providing substrate to facilitate spawning and recruitment of native benthic species may impede the spread of invasive species throughout the tributaries of Lake Erie.