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Great Lakes Article:

Exotic fish species discovered in Lake Superior

Article courtesy of Environmental News Network
October 19, 2001

Wisconsin fisheries biologists have detected a new species of nonnative fish in Duluth/Superior harbor on western Lake Superior.

They suspect the single tubenose goby discovered during a routine survey in late September was a stowaway on a vessel from the St. Clair River, which connects lakes Huron and Erie.

The discovery of the tubenose goby represents its first occurrence outside of the Western Erie/St. Clair River area, according to Dennis Pratt, a fisheries biologist with the Wisconsin Department of Natural Resources. It adds to the growing list of nonnative species introduced by ships and smaller vessels transporting cargo globally and within the Great Lakes.

The tubenose goby is a Eurasian fish species native to the Black and Caspian seas. It was first discovered in 1990 in Michigan waters of the St. Clair River and has since been found in northwestern Lake Erie.

"Duluth/Superior harbor is one of the largest shipping ports on the Great Lakes, and more than one-quarter of the fish species now found in the harbor are not native to Wisconsin," Pratt said. "Many of them were likely carried here in the ballast water of ships, and that may be the case for the tubenose goby."

The fish is about one-and-three-quarters inches long and less than a year old. Biologists don't know whether the single specimen is the result of natural reproduction within the harbor or was an individual transported as a very young fish this summer directly from the lower Great Lakes.

Michigan biologists have found that tubenose goby populations grew after their initial discovery but today are still considered a rare species in the St. Clair River area.

Their population pattern is different from that of the exotic round goby, which was discovered in Lake St. Clair during the same time period. The round goby has expanded its range to all five of the Great Lakes, developing abundant populations at some locations. Biologists anticipate that the round goby may have serious impacts on native fish communities.

Biologists are struggling to control a variety of exotic species that have invaded the Great Lakes. Since 1986, public and scientific attention has been focused on another aquatic invader in the Great Lakes, the zebra mussel. These tiny striped mussels who clog water intake pipes and crowd out native species are relative newcomers in a long history of invaders, from rainbow smelt, alewife, and lamprey to the recently introduced ruffe and spiny water flea.

Gobies are considered undesirable because they can compete with native fishes for habitat and change the balance of the ecosystem. They are already causing problems for other bottom-dwelling Great Lakes natives, especially sculpins. Gobies eat fish eggs and young, take over optimal habitat, spawn multiple times a season, and can survive poor water-quality conditions.

On the positive side, round gobies eat large quantities of zebra mussels, which are causing an increasingly large number of problems because of their huge reproductive output.

Pratt and other fisheries biologists don't know what effects the tubenose goby will have on the ecosystem, but they suspect the impacts won't be as severe as those caused by the round goby.

Noting that ecological impacts can vary substantially from area to area, Pratt said, "It's too early to speculate the potential impacts of this new fish in Wisconsin."

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