Aquatic Exotics

“Since the 1800s, scientists have identified more than 160 invaders – fish, crustaceans, aquatic plants and species of plankton – that have successfully infiltrated and found a permanent home in the Great Lakes. On average, that is one new species successfully integrating into a delicately balanced ecosystem every 11 months.” - Environment Canada

The threat that invasive species pose to our Great Lakes has been well documented. In recent years, the spotlight has shifted as these aquatic invaders have found new homes in inland lakes and waterways within the province of Ontario:

Currently, Ontario’s lakes and waterways are facing a major threat– the Round Goby. This aggressive bottom-dwelling fish originated from Eastern Europe, and through ballast water introductions was introduced to the St. Clair River in the late 1980’s. Round Gobies have been confirmed in all of the Great Lakes, as well as inland waters in the state of Michigan. In July, in the Trent Severn Waterway at the town of Hastings round gobies were also discovered.

This 3 – 5 inch long fish is currently poised to spread further into inland lakes in Ontario. Why the Concern? Round Gobies can spawn 4 to 6 times a year – rapidly building population size and displacing native bottom dwelling species. Gobies are also well known for their aggressive nature and stealing bait off anglers’ lines. When not feeding on bait, small fish, or fish eggs, adult gobies eat zebra mussels. This fact does not render the round goby a “blessing in disguise”, it in fact poses a serious threat to fish and waterfowl that may feed upon the round goby. While filtering algae from the water, zebra mussels potentially bioaccumulate toxins that are present in the water. By eating the zebra mussels,round gobies are potentially increasing the concentration of toxins available to fish and wildlife that prey upon the goby.

Round Goby Identification Chart

Despite predation by walleye and other predators, gobies have continued to flourish, and in the St. Clair River, have been attributed to the decline of both the native logperch and the mottled sculpin.

As a resort, cottage or camp owner, recreational boater, angler, camper, or outdoor enthusiast, you can stop the spread of these invasive species. Never use non-native fish species as bait, and always wash equipment before moving between water bodies with either hot water (>40°C), high-pressure water (>250 psi), or dry your equipment for at least 5 days. Residual lake water can contain plankton species, stem fragments, or fish eggs from infested waters that can spread to other lakes.

The scallop shaped fin on the underside of the fish and black spot on the dorsal fin can be used to distinguish the goby from native species that look similar. If you catch a goby while fishing, preserve it in alcohol or freeze it. Do not throw round gobies back alive. It is illegal to release baitfish from one lake to another, and to use round gobies as baitfish.

For more information on the round goby or other aquatic invasive species, or to report a sighting, contact the Invading Species Hotline at 1-800-563-7711, or visit us online at 

This article was originally released in October 2003 and has been reprinted with thanks to the Ontario Federation of Anglers & Hunters.
Ontario Federation of Anglers & Hunters Logo


NOTO 386 Algonquin Avenue, North Bay, ON P1B 4W3 • T 705.472.5552 • F 705.472.0621 •
Website designed by Sofa Communications