There and back: changes in the size structure of seasonally migrating round goby in Lake Ontario.

Session: Invasive Species (3)

Christopher Pennuto, Buffalo State College, Biology Dept., [email protected]
Knut Mehler, Great Lakes Center at SUNY Buffalo State, [email protected]
Eric Bruestle, SUNY Buffalo State, Great Lakes Center, [email protected]

Abstract

Population size structure is an important feature of migrating organisms with implications for future reproductive success, nutrient translocations, and conservation efforts. The round goby (Neogobius melanostomus) invaded Lake Ontario, USA over 25 years ago and it moves offshore to deeper waters in winter and returns to nearshore waters in the spring. We assessed round goby density and size structure using underwater video to document population conditions when the fall migration commenced and again when it returned in the spring. The departing goby population was dominated (65%) by adult fish >5 cm TL, whereas the returning population was predominately (62%) juvenile fish < 5 cm. We speculate that the loss of larger fish during the winter in offshore waters represents a potentially significant nutrient translocation by round gobies. Possibly, offshore or migratory habitats contain fewer refugia, making larger fish vulnerable to offshore predators in winter or during migration. In support of this possibility, stable isotope and gut content data suggest Lake Sturgeon consume large numbers of round goby and predominately fish in the 4-6 cm size range.