What do Round Gobies look like?Round Gobies are bottom-dwelling fish that were introduced to the Great Lakes from central Eurasia via the ballast water of large, ocean-going cargo ships.
Why are Round Gobies considered a nuisance?With their introduction into the Great Lakes, Gobies have created significant economic and ecological impacts. The four areas below explain these impacts.
- Food Chain Impacts: Fishery managers have found that Gobies have been able to compete successfully with native, bottom dwelling fish such as sculpins and darters. Fishery managers have found substantial reductions in local populations of sculpins in areas in where gobies have become established. The Goby invasion has impacted the food chain of recreationally important fish such as smallmouth bass and walleye.
- Direct Predation: While gobies may compete with sculpins for food or drive them from their preferred habitat and spawning area, laboratory experiments have shown that gobies will eat darters and other small fish. This finding is of concern, because gobies have also been shown to feed on the eggs and fry of lake trout, which has been observed in laboratory experiments. Combine this with the already limited reproduction of the lake trout in the Great Lakes and the potential collapse of an economically significant fishery is possible.
- Contaminants Transfer: On the positive side, round gobies eat large quantities of zebra mussels, another invader that is causing an increasingly large number of problems because of its huge reproductive output. As filter feeders, Zebra mussels, consume toxins that are found throughout the Great Lakes. Zebra mussels are an important component of the gobies' diet in their native range; and, in laboratory studies in North America, a single round goby can eat up to 78 zebra mussels a day. However, it is unlikely that gobies alone will have a detectable impact on zebra mussels. The round goby is expected to be one of several species (including ducks, crayfish, diseases, and other fish species) that eventually will reduce the abundance of zebra mussels. The concern about this fact is that Gobies are preyed upon by several sportfish species (e.g., smallmouth and rock bass, walleyes, yellow perch, and brown trout). Because the diet of round gobies consists predominately of zebra mussels, there may be a direct transfer of contaminants from gobies to sport fish, which could increase the health concerns about eating fish.
- Nuisance Competition: One of the more annoying impacts of Gobies is their aggressiveness with regard to recreational fishing. These fish aggressively take bait from hooks. Anglers in the Detroit area have reported that, at times, they can catch only gobies when they are fishing for walleye.
How do Gobies affect recreational users?Anglers – Recreational anglers are most affected the most by Round Gobies. Specifically, gobies compete with popular gamefish and aggressively take bait from hooks.
Where are Round Gobies currently found?In 1990, round gobies were found only in the areas adjacent to the St. Clair River: Lake St. Clair and in the first 2 km of the upper Detroit River. By 1995, they had spread to Duluth-Superior Harbor, in Duluth, Minnesota (Lake Superior), Montrose Harbor north of Chicago (Lake Michigan), and Ashtabula River in Ohio (Lake Eric).
What is the potential for Round Gobies to spread elsewhere in U.S.?Because the gobies have entered into the Mississippi River drainage, their range will naturally expand beyond the Great Lakes. However, anglers need to learn how to identify Round Gobies and not use it as bait. Preventing this practice will help to reduce the spread of gobies.
Short term benefits of round gobies don’t override long term impacts
- Zebra Mussel Predator - Round gobies eat large quantities of zebra mussels, another hitchhikers that is causing problems because of its huge reproductive output. Zebra mussels are an important component of the gobies' diet in their native range; and, in laboratory studies in North America, a single round goby can eat up to 78 zebra mussels a day. However, it is unlikely that gobies alone will have a detectable impact on zebra mussels.
- Game fish Prey - While gobies are preyed upon by several sport fish species (e.g., smallmouth and rock bass, walleyes, yellow perch, and brown trout), there may be a perception that gobies are beneficial for fishing. However, because their diet consists predominately of zebra mussels, there may be a direct transfer of contaminants from gobies to sport fish, which could ultimately harm humans who consume their catch.
How can I prevent the spread of Round Gobies?Learn to identify gobies. To enable biologists to track the spread of round gobies, up-to-date information on new sightings is needed. Your assistance is extremely important. If you catch a round goby outside the areas noted on the map indicating goby range, preserve the fish either in alcohol (grocery store rubbing alcohol is fine) or by freezing it. Then contact your state fisheries management agency or a Sea Grant institute. Be prepared to describe when and where you caught the fish (the name of the lake or stream, and the nearest town). New sightings can be confirmed only by identification of a captured fish. Verbal reports cannot be used because sculpins can be easily mistaken for gobies.
What else can I do?
- Follow procedures to eliminate the spread of all nuisance species.
- Help inform others.
- Get involved in policy and legislative solutions.