“There's definitely going to be some this year,” he said. “That's a 27-pound fish, and there's going to be a lot of them. I think we'll see 150-200 of them this year, but there were two or three years where we didn't have any.”

The anecdotal evidence from Lake Michigan’s charter captains seems to support a recovery of the shrinking Chinook, or king, salmon the lake has seen over the past several years. And while that’s a positive sign, the scientists and fisheries managers whose business is Lake Michigan aren’t yet convinced that Lake Michigan’s troubles are over.

Lake Michigan supports a billion-dollar sportfishing industry out of dozens of ports up and down the coasts of Michigan, Indiana, Illinois and Wisconsin. It isn’t just the charter captains whose livelihoods depend on a healthy lake. It’s also the people who fuel the boats, sell bait and house and feed the tourists, from Sturgeon Bay to Chicago to Petoskey and hundreds of places in between.

But not everything is sunshine and beaches on Lake Michigan, the only Great Lake entirely within the United States. Thanks to invasive species, zebra and quagga mussels in particular, creatures at the lower end of Lake Michigan’s food web are struggling to survive. The situation is similar to that of Lake Huron, which six years ago saw the collapse of the alewife, a non-native fish that had become the most important food source for Lake Huron’s predators.

Squeezed by a lack of food, increased predation and harsh winters, the alewives died off. Without alewives, Chinook salmon either starved or left Lake Huron’s main basin in search of food. The loss of both species in Lake Huron’s dominant food-web dynamic converted Lake Huron into an entirely new and still-evolving ecosystem virtually overnight.

And while Lake Michigan has some safeguards that are built in and others that are human-assisted, researchers worry that a similar predator-prey imbalance exists in Lake Michigan, where a loss of the salmon population would be nothing less than devastating.

“Those port towns are driven by salmon fishing and to the extent we can minimize the fluctuations between predator and prey, I’m hoping we can promote better balance,” said Randy Claramunt, a Michigan Department of Natural Resources biologist. “
Complicating matters further is tension between management agencies who disagree over what their priorities should be. Some believe the economic benefits of a salmon-based fishery should trump all; others believe the restoration of native lake trout is most important. In the face of what everyone agrees is a shrinking prey base, the outcome of that debate could shape Lake Michigan for decades.

Where’s the food?

Much like Lake Huron, Lake Michigan has seen a tremendous dropoff in productivity – the amount of food energy in the system – since the arrival of quagga mussels in the late 1990s. Where zebra mussels cleared the water in shallow, near-shore areas, quaggas colonized the deeper parts of Lake Michigan.

Zebra mussels (left) live in the near-shore waters of the Great Lakes, but quagga mussels (right) have colonized the deeper waters of lakes Huron and Michigan, causing dramatic changes in the food web. (USGS photo)

“Some people view the sea lamprey as probably the worst thing that has happened to us,” said Paul Peeters, the Wisconsin DNR’s coordinator for northern Lake Michigan. “I say it’s quagga mussels. Lampreys took out predators, but we can manage and restock predators. Quaggas have changed the food web so dramatically that it’s probably not something we can manage.” Quaggas filter the open lake of tiny plant and animal matter that was food for small crustaceans like daphnia, misis and diporeia. Those creatures were important in the food web because they rose off the lake bottom at night to feed in the open water, where fish like alewives, whitefish and baby lake trout would feed on them.

But the mussels took away their food, and without food, misis and diporeia have dropped off considerably and in some cases disappeared. Without them migrating upward, the lake’s nutrients are trapped on the bottom where most fish can’t get to them.

“Before dreissenid (zebra and quagga) mussels, a lot of that energy came up and ended up in fish muscles,” Peeters said. “(The mussels) have tied it up. It’s not available to anything else. Now it’s locked up in mussel flesh.”

That “nutrient sink” effect has taken its toll on all of Lake Michigan’s prey fish, from bottom-hugging sculpin to open-water alewives.

“Preyfish biomass has never been lower, and we’re saying that for the third straight year,” United States Geological Survey researcher David Bunnell told the Great Lakes Fishery Commission at its meeting in March.

Bunnell and his colleagues concluded in their Lake Michigan report that predation could not be solely responsible for the dearth of prey fish, mainly because it also involved species that salmon don’t eat.

The alewives’ biomass – the raw tonnage of alewife fish meat – is down significantly, but there has not been a wholesale collapse like that seen in Lake Huron. In fact, alewives still seem to be multiplying vigorously.

That’s partially because southern Lake Michigan is deeper and warmer than Lake Huron, giving the weather-sensitive alewives a haven from winter. The thing biologists are concerned about is that fact that alewives can’t seem to reach adulthood, probably because the decline in overall prey puts them at a higher demand.

According to Peeters and Claramunt, a population that consists only of young fish is in a perilous position.

“It would be a lot better if some of the little alewives could become bigger fish,” Peeters said. “I would argue that this is the symptom of a system that’s very unstable. Alewives are very susceptible to weather. If you’re counting on the little fish to provide a year class, you could find yourself in a situation where you don’t have any alewives.”

Action and reaction

Informed in part by what happened in Lake Huron, fisheries managers have made significant cutbacks to Chinook stocking in an effort to better match the predators with the available food. The four states involved in managing the lake had been putting 4.3 million salmon into Lake Michigan every year. In 2006 that number was reduced to 3.2 million, and early returns from this fishing season seem to indicate the reduction is working.

Overall the Chinook salmon are still smaller than they were five or 10 years ago. But they appear to be healthy, and average fish weight and length ticked up last year over 2007. A significant portion of Lake Michigan’s Chinook salmon come from natural reproduction above and beyond stocking – the number could be more than half – but Lake Michigan is not producing the emaciated, starving fish Lake Huron did five years ago.

The prey base is still down, leading some to wonder whether the stocking cuts were enough.

“A lot of us wanted to cut back faster and deeper than we did, but it’s counterintuitive to tell sport fishermen that we’re going to give them better fishing by stocking fewer fish,” Peeters said. “Some of us are still very worried that we didn’t go far enough fast enough because we don’t want to go where Lake Huron is.”

Because the Lake Huron episode showed just how quickly things can change, Claramunt said it’s crucial that fisheries managers recognize and anticipate places where they can make a difference.

“If we do want to make changes, you don’t want to wait until two or three years down the road,” he said. “We need to look at it and pay attention and to the extent we can mitigate these disturbances we should.”

One of the great challenges of managing Lake Michigan is the number of players involved, Peeters said. DNRs from Wisconsin, Illinois, Indiana and Michigan, plus the Ottawa-Chippewa Resources Authority, all have a say in Lake Michigan fishery decisions.

“It’s very frustrating when you have a system like Lake Michigan, and the four states and the tribes have to agree on everything we do going forward and you can’t get a consensus,” Peeters said.

Another key player is the U.S. Fish and Wildlife Service, which still stocks 2 million lake trout per year in Lake Michigan, a strategy not everyone agrees with.

“Some people want to go full force with that, even if it means co-opting the entire forage base,” Peeters said. “The forage base is low by anyone’s measure, but they’re talking about stocking more lake trout, not fewer.”

Any perceived imbalance is watched closely by biologists around the region, who learned from LAke Huron just how quickly and dramatically things can change.

"(Lake Michigan) is a billion-dollar fishery," said Jim Johnson, a Michigan DNR biologist who is studying Lake Huron's ecosystem overhaul. "Lake Huron is small potatoes compared to Lake Michigan. Everybody

Part I : Lake Huron's new food web
Part II: Lake Huron: Seeking new balance