Exotic fish such as the round goby can lead to the extinction of native species through competition and predation. Round gobies were first reported by anglers in the St. Clair River in 1990. Since then, round gobies have successfully colonized all five Great Lakes. The fish were thought to have been brought to the Great Lakes in ballast water of ships originating in southern Europe. Several researchers in Canada and the United States are attempting to assess the impact of round gobies on the Great Lakes ecosystem.

The aggressive round goby has already lead to the decline of native mottled sculpins. Round gobies also may affect sport and commercial fishes. Gobies eat eggs of lake trout and sturgeon.

Round gobies are small (8-12 cm), bottom-dwelling fish characterized by a fused pelvic (bottom) fin, frog-like eyes, and a black spot on the dorsal fin. They are found on hard substrates along with zebra mussels, which form much of their diet. Round gobies are aggressive, multiple spawners with an extended reproductive season. Thus, there is the potential for round gobies to produce large numbers of offspring each year. Breeding round goby males have characteristic black colouration in contrast to the usual gray mottled pattern of other gobies. Males guard nests in which eggs of several females are deposited. Round gobies nest in a cavity with a single opening. The guarding male positions himself with his head at the entrance and the fish nips at intruders.

The persistence of round gobies will depend on the existence of local populations. In the summer of 1997, SCUBA divers observed several round gobies reproducing on shipwrecks in Lake Erie. Although round gobies typically reproduce in shallow water, reproducing populations were found on shipwrecks at depths of 10 m or more.

There are over 4,500 shipwrecks in Lake Erie and Lake Huron and more than 200 wrecks in the Pelee Passage of Lake Erie. Since round gobies prefer rocky habitats, shipwrecks and natural reefs are likely spots for breeding populations.

The information that volunteers collect on the distribution of round gobies will help lead to the control of local populations. Anglers and divers can help document the spread of round gobies by participating in the round goby count.

Round Goby Spawning Videos
The following videos were taken in at the University of Windsor during a spawning event we observed in March 2008. The male and female are seen inverting several times, while the female is also seen depositing eggs on the top of the nest.

How To Identify A Round Goby:
Key features of this fish:
- Single pelvic fin
- Young are solid slate gray
- Usually 3"-6" long, but my be up to 10" long
- Bottom dwelling fish

Please report any sightings of this invasive fish!

Dr. Lynda Corkum
Unversity Of Windsor
401 Sunset Ave,
Windsor, Ontario
N9B 3P4
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