Other times, he notes, gobies dive under the gravel and vanish. Jude has watched hungry bass become flummoxed by the gobies' seemingly erratic activity. However, the predatory fish seem to be wising up. Increasingly, anglers are catching game fish that have stomachs full of gobies-suggesting these larger fish may begin reining in the gobies' territorial dominance. Yet that fuels another concern.
Mussels pick up and store toxic pollutants from the water.
Indeed, once a nonnative species is established, eliminating it becomes almost impossible, argues John Mills, Environment Canada's regional director-general in Toronto. Government officials in Canada and the United States have launched campaigns to help boaters and anglers recognize the goby and prevent its transfer to new waters. In particular, Dermott emphasized, gobies should never be used as bait, transported live, or even returned to the waters from which they were caught. The campaign may help limit the fish's migration to inland lakes in Canada, but U.S. officials face a tougher threat outside Chicago. Roughly a century ago, the Chicago and Calumet River systems were engineered to flow from Lake Michigan toward the Mississippi River.