Nest defense by the non-indigenous fish, the Round Goby, Neogobius melanostomus (Gobiidae), on a shipwreck in western Lake Erie

This is the first documentation of nest defense by a male Round Goby (a non -indigenous fish) on an exposed nest in North America. Our observation of R ound Goby nesting behaviour on a shipwreck in the western basin of Lake Eri e using a video camera indicate that these fish spawn at much greater depth s (7-11 m) than previously reported (less than or equal to 2 m). Of species that approached the nest (Rock Bass, Ambloplites rupestris; Smallmouth Bas s, Micropterus dolomieu; Yellow Perch, Perca flavescens; Logperch, Percina caprodes; Round Gobies, Neogabius melanostomus), most behavioural interacti ons occurred between the guarding male and other Round Gobies. During 12 mi n of observation, there were 63 instances in which a Round Goby approached the nest and in four cases, intruders fed on eggs at the periphery of the n est. In response, the guarding male approached (34 times), chased(18 times) and hit (4 times) Round Goby intruders. Response by the resident goby to t he presence of Rock Bass tone swam by and seven approached) resulted in six approaches, four chases and one kit. The resident male responded to juveni le Smallmouth Bass (three swam by and seven approached) only once by approa ching the intruder. The guarding male did not respond to either Logpersh or Yellow Perch, but tao few events were observed to suggest that the absence of a response by a male was typical. We anticipate that recruitment of Rou nd Gobies will increase substantially in Lake Erie owing to the presence of artificial reefs (shipwrecks) and the ability of guarding mates to defend nests effectively.