The round goby, first detected in the St. Clair River in 1990, is a small, pugnacious species that feeds on the fry and eggs of native Great Lakes fish. It aggressively defends its spawning sites in rocky habitats, denying access to native species to prime areas for reproduction. And it forces from their habitat native sculpins and darters, important species in the food chain.

The zebra mussel, which arrived in North American waters in 1985, and the round goby have evolved together in other areas of the world. Both originated in the Black and Caspian Seas area and both are thought to have been brought to this continent in the ballast of foreign freighters.

Round Gobies

Gobies, normally three-to-six inches long, can grow up to 10 inches. They resemble the Great Lakes native sculpin fish but have a distinctive fused pelvic (bottom) fin. The sculpin has two separate pelvic fins and, commonly, a dark spot on the dorsal fin.

Gobies have a well-developed sensory system that enhances their ability to detect water movement, allowing them to feed in complete darkness. This creates a major competitive advantage over native fish in the same habitat.

Gobies prefer a rocky or gravel habitat, generally inhabit the nearshore area but will migrate to deeper water in winter. They can also survive under degraded water quality conditions. This characteristic, coupled with an ability to swim into holes and other crevices, likely allowed gobies to enter and survive in the ballast water of North America-bound ships.

The goby spawns over the summer months, taking advantage of temperature and food conditions. A single female produces 300 to 5,000 eggs, deposited in nests on tops or undersides of rocks, logs or cans, which are then guarded by males.

Zebra mussels

Zebra mussels reproduce rapidly and cause their greatest damage to industry by clogging water intake pipes. Over the past 10 years, estimated zebra mussel costs have totaled $5 billion, with ongoing annual costs to industry of $20,000 to $350,000 per facility. The figures do not include the cost to cottagers: clogged water pipes, and ruined motor boats and beaches.

The mussels have made a dramatic change in the ecosystem because they filter plankton from the water and reduce the amount of energy available for fish. Some parts of the Great Lakes system, such as the Bay of Quinte, have become very clear as a result, sending walleye to deeper waters.

Zebra mussels filter almost everything from their habitat. Organic pollutants get stored in the zebra mussels’ tissue. Before zebra mussels infested the Lakes, most material of that kind would either be absorbed by zooplankton or settle into sediments.

Lake Ontario’s Fishing Industry

A 1995 Canadian federal survey showed sport fishing on Lake Ontario contributed more than $53.2 million to the provincial economy. In 1997, anglers in Canada spent more than 500,000 hours fishing Lake Ontario and caught more than 70,000 salmon and trout.

A 1996 U.S. survey reported an estimated US $56.5 million (C$83.62 million) spent by Lake Ontario anglers.

Estimated value in both countries of the Lake Ontario sport fishing industry: C$136.8 million.

Lake Ontario supports a small commercial fishing industry in Canada (1 million pounds of fish valued at nearly $1 million) harvested primarily from eastern Lake Ontario and the Bay of Quinte. The Canadian portion of the St. Lawrence River also supports a commercial fish harvest: 350,000 pounds valued at $400,000 (1997 figures).

U.S. waters produced a reported $69,000 worth of fish harvested commercially (a figure currently under legal investigation).