"By interfering with mottled sculpin reproduction, the round goby may have a negative impact on the food supply of yellow perch, an important sport fish in Lake Michigan.

Until recently, the mottled sculpin was the second-most abundant fish in the St. Clair River. Now it ranks 13th. And the goby population is soaring.

The round goby, a Eurasian fish that has invaded the Great Lakes, is causing the decline of the mottled sculpin by displacing the native from its spawning sites.

"By interfering with mottled sculpin reproduction, the round goby may have a negative impact on the food supply of yellow perch, an important sport fish in Lake Michigan.

And in Calumet Harbor, the U.S. Geological Service has reported the absence of mottled sculpin nests since the round goby was established in that part of Lake Superior in 1994.

Meanwhile, the native goby - called a sculpin - has two separate pelvic fins, its body has a mottled color pattern with a cream-colored belly, and has no scales.