Killer Gobies Invade Great Lakes

Scientists are warning that a foreign fish introduced into the Great Lakes is boosting toxin levels in game fish and could pose a serious health risk to humans, as well as threaten the sturgeon population.

Round gobies, bottom dwellers that grow to about the size of perch, are aggressive and feast on the eggs of other fish such as sturgeon -- a threatened species in Michigan. Fishermen call them scavengers, and they can survive in poor water conditions, the Detroit News reported.

Experts believe that gobies could pose a health hazard to humans as toxins are passed through the Great Lakes food chain. "Gobies pick up contaminants and could contaminate sport fish which eat gobies," said Lynda Corkum, a biology professor from the University of Windsor who has been studying the goby from Lake Huron to Lake Erie.

The U.S. Environmental Protection Agency has issued an advisory recommending that people not eat more than one meal per week of species caught in the Great Lakes. Pregnant women are advised to eat even less.

Biologists are so concerned about the impact of the round goby that Michigan fisherman now are prohibited from transporting the species in bait buckets, and tests are being conducted using electrical currents to stop the interloper from spreading even farther.

Studies last year showed that gobies have been foraging on the sturgeon roe in the St. Clair River, the only known spawning grounds for the game fish in southeast Michigan, said Robert Haas, a Michigan Department of Natural Resources biologist.

"...We found sturgeon eggs in their stomachs," Haas said. "We know sturgeon eggs were abundant on the spawning grounds and over a period of days, they disappeared. We're looking at it intensely."

Haas plans to conduct a study using underwater video cameras this spring to determine how extensive the impact is on sturgeon, a species whose ancestry dates to prehistoric times.

The round goby also is threatening other native fish as its population has exploded throughout the Detroit River, Lake St. Clair, all the Great Lakes and several inland lakes, the Detroit News reported.

The gobies are native to the Black Sea and Caspian Sea, and were accidentally discharged into the St. Clair River more than a decade ago after a foreign freighter emptied its ballast water.