Round gobies are thriving in the Great Lakes Basin because they are aggressive, voracious feeders that can forage in total darkness. The round goby takes over prime spawning sites traditionally used by native species competing with native fish for habitat and changing the balance of the ecosystem. Although gobies belong to a family of fish with a worldwide distribution in both salt and fresh water, they had not been found in the Great Lakes prior to 1990. Presumably, the fish arrived in ballast water discharged by trans-oceanic ships. It can be difficult to distinguish between round gobies and sculpins, but the goby's fused pelvic fin is the best way to tell them apart.
Gobies also are capable of rapid population growth.
They spawn repeatedly during the summer months, and each time, a female can produce up to 5,000 eggs. The males die after spawning. In the United States, studies have revealed that the diet of round gobies includes insect larvae and zebra mussels.