Published July 22, 2012, 12:00 AM

Lake Michigan's salmon populations still fluctuate

Lake Michigan’s salmon fishery is a two-pronged success story. Salmon not only provide a popular fishery for thousands of anglers; the fish also control the population of non-native alewives, a forage species, in the lake.

By: Sam Cook, Duluth News Tribune

Lake Michigan’s salmon fishery is a two-pronged success story. Salmon not only provide a popular fishery for thousands of anglers; the fish also control the population of non-native alewives, a forage species, in the lake.

But finding the right ratio of salmon to the forage fish they feed on hasn’t always been easy, biologists say.

Chinook (or king) salmon and coho salmon were first introduced to the lake in the 1960s, said Steve Hogler, a fisheries biologist with the Wisconsin Department of Natural Resources at Green Bay. The population took hold, and by the 1980s, salmon fishing was a phenomenon. The alewife population was held in check. Life was good.

“But by the 1990s, we were having nutritionally stressed salmon,” Hogler said. “We were stocking more salmon into Lake Michigan than there was food out there to feed them.”

In addition, an outbreak of bacterial kidney disease killed thousands of salmon in the late 1980s.

It was 2006 before stocking numbers were reduced, Hogler said.

“We stocked fewer fish, and the fishing turned around fairly rapidly,” he said.

Now, about half of Lake Michigan’s salmon are naturally produced, mostly in a few Michigan streams. About 4 million salmon are stocked annually by Wisconsin, Illinois, Indiana and Michigan. Wisconsin stocks about 1.12 million per year.

Salmon fishing has declined slightly in the past three or four years, but before that, catch rates for salmon were as high as they had ever been on the lake, Hogler said. The DNR still is trying to figure out how many fish can be stocked without adversely affecting the alewife population.

The size of Lake Michigan Chinooks has declined somewhat, Hogler said.

“We may be seeing the impacts of lowering forage numbers,” he said. “The winners of fishing contests this year have been between 20 and 24 pounds. A few years ago, we were seeing some up to 30 pounds. That was probably due to a strong alewife year class that’s since been eaten away.”

There also is concern that invasive quagga mussels may be filtering some organisms that alewives need to survive.

Meanwhile, the number of salmon anglers on Lake Michigan is declining, Hogler said. He cited several reasons for that.

“Like other states, we’ve seen a decline in people fishing,” he said. “There are scares about contaminants in the fish and about fewer being stocked. And there are other factors, like gas prices.”

Lake Michigan’s salmon, although they live for only four or five years, do carry contaminants, namely PCBs (poly-chlorinated biphenyls) and mercury. People are advised to limit the number of salmon meals they eat.

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