Susceptibility of tethered round gobies (Neogobius melanostomus) to predation in habitats with and without shelters

We determined the susceptibility of the nonindigenous round goby (Neogobius melanostomus) to predation in sandy habitats with and without shelters in Lake St. Clair. Six round gobies were tethered in a 1 m(2) area and videotaped in three habitat types: sand without shelters, sand with shelters (flowerpots), and sand without shelters within an enclosure (control). Daytime trials lasted 90 min; there were 20 replicates per treatment. More round gobies were missing from sand habitats without shelters (17/120) than from sand habitats with shelters (7/120) or control (0/120) habitats (X(2) = 18.25, P < 0.005), indicating that there is a greater potential risk of predation in open habitats than in habitats with cover. Round gobies that were missing from tethers versus those that remained differed significantly in mean (+/- SE) total length (72 +/- 4 mm versus 89 +/- 1 mm) and weight (5.2 +/- 0.8 g versus 9.1 +/- 0.3 g). Round gobies removed from tethers were smaller than those that remained. Small mouth bass (Micropterus dolomieu) were videotaped in the habitats where tethered fish were missing. Seven yellow perch (Perca flavescens) were retrieved that were entwined in tethers and in each case a perch had a round goby in its mouth. Predation risk to a small round goby is high in sandy habitats without shelters.