Changes In Great Lakes Threaten Transplanted Fish

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Forty years ago, fisheries biologists in Michigan dazzled the nation when they took salmon from the Pacific Ocean and planted them in the Great Lakes. Their success transformed the lakes into a sport-fishing paradise and created a multi-billion dollar industry. But now invasive species have changed the food web in the lakes. Salmon are struggling to find food, and the state might end one of its stocking programs.

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Forty-five years ago, biologists in Michigan dazzled the nation. They took salmon that were native to the Pacific Ocean and transplanted them to the Great Lakes, turning the region into a sport fishing paradise.

But Peter Payette of Interlochen Public Radio reports that the grand experiment may be coming to an end, as changes in the lakes threaten the salmon fishery.

PETER PAYETTE: There's a historical marker at the Platte River State Fish Hatchery. It was here in 1966 that salmon, hatched from eggs taken from Oregon, were first successfully introduced into Lake Michigan. At this hatchery, a few miles from the lake, millions of tiny salmon are swimming in long cement tanks. Water from a nearby creek pours through a series of bath fills, simulating the current of a stream.

(Soundbite of rushing water)

PAYETTE: Hatchery biologist Aaron Schweitzer says two million three-inch long fish are almost ready to be released.

Mr. AARON SCHWEITZER (Biologist, Platte River State Fish Hatchery): They are going to get loaded on to trucks and shipped out to different ports across the state, both on Lake Huron and Lake Michigan.

PAYETTE: But these lakes are not as hospitable to the salmon as they once were. That's particularly true for Lake Huron, where Ed Retherford is a charter boat captain. He says in the old days, on a weekend in Rockport, he'd see cars with boat trailers backed up for a mile or two just waiting to launch. But no more.

Captain ED RETHERFORD (Sport Fishing Charter Boat): You'd be lucky, except maybe for the Brown Trout Festival, to see 20 boats there, you know, on a weekend. That's, I mean, it just decimated that area.

PAYETTE: The most popular salmon, Chinook or king salmon, largely disappeared from Lake Huron seven years ago. The salmon's demise in Huron followed the disappearance of its favorite food - little fish called alewives. Scientists say there were too many salmon eating the alewives, as well as problems lower down on the food chain caused by invasive mussels.

State fisheries biologist Jim Johnson says salmon didn't adapt and eat something else.

Mr. JIM JOHNSON: They didn't have enough to eat. They wouldn't switch to eating round gobies, and they died of malnutrition.

PAYETTE: The changes in Lake Huron have been significant. In some ways it's more like the ecosystem it was before humans started engineering it. Since neither salmon nor alewives are native to the lake, with them out of the way, native fish like walleye have returned.

Fishery managers continued to stock one and a half million Chinook salmon in Lake Huron every year. But biologist Jim Johnson says the walleye eat most of them, and he says Lake Huron can't support a big salmon fishery anymore.

Mr. JOHNSON: It's just not realistic. The lake doesn't offer that, and there's nothing the DNR can do to change that.

PAYETTE: The question now is whether to stock any Chinook salmon in Huron at all. Giving up on the most popular sport fish in the Great Lakes is hard to swallow for officials and anglers, but most see the writing on the wall.

On the western side of the state, there are now worrying signs the same fate might be in store for Lake Michigan. There are still lots salmon in Lake Michigan, but charter boat captain Denny Grinold says something clearly went wrong last fall. He says the big salmon, the four-year-old fish that come up into the rivers to spawn in August, never showed up.

Mr. DENNY GRINOLD: You keep looking for them. You keep looking for them. You go out and you fish the patterns that you've fished in the past where the Chinook, those large Chinook should be there, and they just weren't there.

PAYETTE: Even if last year was a fluke, research provides little comfort for the future. The state carefully tracks conditions for salmon in Lake Michigan, things like how much food is available, the weight of fish and how many are being caught.

Jim Dexter manages the lake for the Department of Natural Resources. He says the trends for salmon are not good.

Mr. JIM DEXTER (Department of Natural Resources): It's not a happy place. I mean, the lake is very perturbed. It's certainly not a stable, quality ecosystem. I mean, it's working right now. It's producing a fishery. People are happy, but it's tenuous.

PAYETTE: And there's not much the state can do to change that. If salmon go from Lake Michigan, that would be the end of what might be the world's largest fish farm.

For NPR News, I'm Peter Payette.

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