by Peter Payette for The Environment Report
The people who manage salmon in Lake Michigan will have to decide soon how many fish to put into the lake. The salmon fishery is a manmade industry in the Great Lakes. It’s produced by planting millions and millions of fish in the lakes. But keeping the salmon population in balance with the food supply is a challenge these days. And some scientists are raising new questions about the salmon’s demise in Lake Huron and whether that can be stopped in Lake Michigan.
Salmon were brought in from the Pacific Ocean.
Some fish have learned to breed in the wild but historically, if you caught a salmon in the Great Lakes, it was born in a tank.
But by 2002, that was no longer true in Lake Huron. That year, researchers observed something they didn’t believe, at first. Four out of every five salmon were wild.
Jim Johnson is a state fisheries biologist based in Alpena. He says they assumed there was something wrong with the data.
“And we thought maybe it was a tick that would stabilize later on. But every year since then it’s been about 80 percent. It wasn’t just a flash in the pan it was a permanent change.”
The change might sound like good news: more fish.
But there were too many, far too many.
They ran out of food and died off.
Today, the once famous salmon fishery in Lake Huron is pretty much gone.
And Jim Johnson says it all happened rather suddenly.
“The Great Lakes are big waters; you think of things happening slowly in such big waters. This was relatively rapid.”
What happened in Lake Huron was the fish adapted well to some rivers in Georgian Bay.
Johnson estimates that while the state was putting three million fish in the lake each year, as many as 14 million wild fish would be born in Georgian Bay.
That overwhelmed the food supply of the whole lake.
You might say that the salmon, an exotic fish, became an invasive species in Lake Huron and wrecked the food web.
Recently, scientists have begun to talk about the fact that Lakes Huron and Michigan are connected by the Straits of Mackinac.
They know fish pass through the Straits but have generally believed it’s a minor factor.
But one scientist in particular is now questioning that assumption.
Rick Clark does research through Michigan State University. Clark noticed something unusual about fishing in Lake Michigan during the past decade.
He says the fishing has been nearly as good as it was back in the eighties: the best fishing ever on Lake Michigan.
But anglers spend about half as much time fishing as they did back then.
“So that meant that half the number of fishermen were catching just as many fish. Which is hard to explain except that there must’ve been more fish out in the lake.”
His hypothesis is that lots of fish born in Lake Huron are coming over to feed in Lake Michigan.
It’s a just a hypothesis, but it’s a troubling one.
Clark says if millions of wild salmon are coming over from Georgian Bay, the salmon fishery in Lake Michigan could collapse too.
But Mark Ebener doesn’t think that’s happening.
He’s a fisheries biologist for the Chippewa Ottawa Resource Authority.
Ebener says the salmon fishing is horrible in Lake Huron right now.
“If there really was (sic) that many wild fish being produced in Lake Huron and particularly in Georgian Bay and moving into Lake Michigan, we would see substantial better fisheries than what we see… they’re not going to make a beeline for Georgian Bay into Lake Michigan.”
Ebener says it would take centuries for the salmon to develop such a specific migration pattern.
But the managers of Lake Michigan are anxious about this very possibility.
And it is something of a wildcard as they decide how to maintain the state’s prized salmon fishery.
You can listen to this Environment Report series: The Collapse of the Salmon Economy to learn more.