The round goby has not yet been sighted in Iowa waters, but this fish is becoming increasingly common in the Great Lakes. This species is native to the Black and Caspian Seas and in all likelihood entered the United States from the discharge of ballast water released from transoceanic vessels. The goby has the potential to enter the Mississippi River through the Chicago Ship and Sanitary Canal and down the Illinois River.

The largest round goby specimens found in the Great Lakes have been about 180mm (7 inches), but they get larger in their native range. Females mature at one year of age, as small as 58mm, and spawn every 20 days, up to six times, during the spring. Total fecundity is about 5000 eggs.

Impacts of a goby invasion in Iowa are uncertain; however, we would prefer that they would not make it to our state's borders. In other regions where the goby has been established, such as the Great Lakes, they have had a severely negative impact on native fish populations. Populations of mottled sculpins (Cottus bairdi) are already dwindling, and may be driven into extinction from round gobi competition. Other species that may be affected include logperch and lake sturgeon- a species that is already endangered in Iowa. If round gobies colonize the Mississippi River, there is concern over the impacts they may have on darters, several of which are listed on the Federal Threatened and Endangered Species List.

Gobies are larger than most species they compete with, and feed in total darkness using their highly sensitive lateral line to detect prey. They are known to be aggressive defenders of their territory and displace native fish, and are tolerant of poor water quality. These factors give them a competitive advantage over native species. They also feed heavily on small bottom dwelling fishes, such as sculpins and darters. These small species are heavily utilized by our native game fish species, and the impacts of a round goby infestation are more than likely to be detrimental to sport fishing.

If you think you have caught a round goby please contact your local Iowa DNR fisheries biologist.