Since the early 1800s, over 140 exotic species have invaded or been introduced into the waters of the Great Lakes basin. In most cases, these introductions have occurred as a result of human activities including shipping, building of canals, and deliberate releases. Several of these species have had substantial impacts on the Great Lakes resource. For example, the sea lamprey was responsible for the disappearance of Lake Michigan's lake trout populations, which now are maintained in the lake only through stocking. Millions of dollars are required annually to manage, control, and reverse the impacts of nonindigenous aquatic nuisance species in the Great Lakes.
The round goby (Neogobius melanostomus Pallas).
Many of these species first introduced into the Great Lakes have been transferred to inland lakes, rivers, and streams both near to and far from the Great Lakes. Often this transfer is a direct result of human activity such as the building of canals. The Chicago area canals built to allow reversal of the flow of the Chicago River have enabled two recent invaders, the round goby and the zebra mussel, to move downstream from Lake Michigan into the Illinois and Mississippi rivers, respectively. The Illinois Natural History Survey is working with a panel of municipal, state, and federal entities in the design of an experimental barrier intended to curtail the downstream movement of species from Lake Michigan into the Illinois River (and vice-versa). The first phase of this barrier will be installed by the Army Corps of Engineers in the summer of 2000. Subsequently, researchers at the Survey's Lake Michigan Biological Station will begin studying the ability of fish to move across the barrier, which will provide insight into the feasibility of barriers as deterrents to the spread of exotics.
Recreational boating and fishing are other mechanisms by which exotics are spreading to inland waters. For example, six lakes in the greater Chicago area have been confirmed as infested with zebra mussels, which most likely were introduced into these lakes on boats or boat trailers used previously in infested waters (e.g., Lake Michigan). Likewise, the round goby has been introduced from the Great Lakes into two inland rivers in Michigan, most likely as a result of an angler using them as bait. These exotics can cause a myriad of problems (e.g., food web disruption, reduced biodiversity, clogging of water intakes, increased weed growth), and cannot be eliminated from a system without causing increased harm.
A statewide survey of boaters and anglers to determine their knowledge and attitudes regarding exotic species indicated that this group lacked information on the potential spread of exotics via fishing and boating activities and equipment. Therefore, with funding from the Illinois-Indiana Sea Grant College Program and the Great Lakes National Program Office of U.S. EPA, we have initiated several outreach projects targeted at boaters and anglers. Also, we have produced large metal "Exotic Species Advisory" signs for placement at boat landings around the Illinois shoreline of Lake Michigan.
These signs caution boaters about the potential impacts of exotics, and encourage boaters to take the necessary steps (e.g., washing the boat before traveling to another waterway) to prevent accidental spread of these species. We have produced a brochure for boaters containing background information on exotic species and steps for preventing their spread. We then made these brochures widely available to the boating public through venues such as boat shows and safe-boating classes sponsored by the Illinois Department of Natural Resources. We have also developed displays for baitshops that assist anglers in identifying the round goby. A preliminary survey of anglers in the Chicago metropolitan area indicated that 45% of anglers cannot distinguish the round goby from a common native species. This confusion could contribute to anglers unknowingly spreading the round goby. Sea Grant also has funded a project that involves providing baitshops with baitbucket stickers. These stickers will remind anglers not to release unused bait into a lake or river, because that can result in non-native species (e.g., Eurasian watermilfoil) becoming established. We hope that these outreach projects combined with the experimental dispersal barrier will advance the campaign to prevent the spread of exotic species from Lake Michigan to inland Illinois.
Patrice M. Charlebois, Center for Aquatic Ecology
Charlie Warwick, editor