Stocking Mille Lacs with new walleyes seems like a neat fix for a broken lake that is one of the natural touchstones that makes Minnesota — Minnesota.

It worked for Leech Lake. It worked spectacularly for Red Lake, when its walleye population collapsed in the 1990s.

But artificially adding fish to Mille Lacs next spring would probably quell only the human problem that’s arisen from a painful blow to the state’s fishing culture. The natural ones that lie below the lake’s notoriously rough surface are far more complicated, say fish biologists.

Minnesota’s most popular fishing lake, they say, has changed fundamentally in ways not well understood, but which could be permanent. Mille Lacs has plenty of little fish — they just aren’t winning the war of survival.

When the Minnesota Department of Natural Resources (DNR) announced that walleye fishing would abruptly halt on Mille Lacs last week, it triggered the fury of many resort owners and local residents who say the agency and Indian bands have mismanaged the fishery for years.

Many find themselves in mourning for a deeply held Minnesota tradition that may now be on the wane.

“It’s part of the culture,” said Steve Fellegy, a fishing guide who grew up at his parents’ resort on Mille Lacs, a lake he described as the state’s crown jewel. For a generation it was the premier destination on the day of the fishing opener. And it was everyone’s lake. Anglers from the Twin Cities could hook up their boats at dawn on a Saturday morning and be home that night with walleye for dinner.

“You bring home a meal of walleye and celebrate the memories you got while catching the fish,” Fellegy said. “People cherish those.”

But Minnesotans who blame the DNR or the tribes for mismanaging walleyes are missing the larger picture, said James Zorn, executive administrator for the Great Lakes Indian Fish and Wildlife Commission.

“There are factors here that are beyond the control of harvest — invasive species, water temperatures, all those bigger issues that should make us wake up,” he said. And tribal members are just as worried as anyone else, he said.

Red Lake experiment

This is not the first time that Minnesota has faced a crisis in the lakes that naturally produce walleyes — big, windy ones such as Leech and Winnibigoshish, where the water movement and gravelly bottoms create good spawning grounds.

Red Lake, the state’s largest, is one of the most famous examples. The walleyes were, quite simply, fished out in the 1990s. It was a lethal combination of sport fishing, tribal netting for subsistence and commercial sales, and poaching.

In the mid-1990s, the Red Lake Band of Ojibway, which owns all of Lower Red Lake and much of Upper Red Lake, banned commercial fishing and netting. A year later, the DNR closed the lake to walleye sport fishing.

Then they came up with a plan to fix it.

“We had an equal role,” said Don Pereira, head of fisheries for the DNR, who studied Red Lake for his graduate school research project.

The joint committee formed to manage the lake made the difficult decision to stock it with walleye fry from the Lake Vermilion system. The tactic risked destroying the Red Lake walleye genetics that evolved to make them uniquely able to thrive in that particular lake ecosystem.

But waiting to see whether the few remaining Red Lake walleyes would recover on their own would take a decade or more.

So they stocked it with 33 million to 40 million fry in 1999, 2001 and 2004.

“The success was so spectacular, it didn’t take 10 years,” Pereira said. “Only seven.”

Today, Red Lake is teeming with walleyes, and quotas are carefully managed by the tribe and the DNR.

‘Walleye are just hungry’

What worked on Red Lake, however, won’t necessarily work on its neighbor to the south.

Red Lake is pristine, without a single invasive species. Mille Lacs, on the other hand, is now home to three invasive species that, combined with other significant environmental shifts, are rapidly changing the dynamics of the lake below the surface.

Climate change, for example, could be threatening one of the walleyes’ primary food sources, tullibees. That species, also known as cisco, is a cold-water fish trying to survive in a shallow lake that, on average, is getting warmer. Tullibee numbers fluctuate from year to year along with average water temperatures, but have generally trended downward in Mille Lacs and many other Minnesota lakes.

Without tullibee to eat, walleyes instead eat each other, said Paul Venturelli, a fish biologist at the University of Minnesota, who last year headed a panel of scientists that reviewed the walleye problem for the DNR.

“This is a situation where walleye are just hungry,” he said.

Walleyes also eat perch, but they too appear to be declining in Mille Lacs.

Pike and bass — which like to eat young walleyes, too — are on the rise, perhaps because they fare better in clear lakes that also have a lot of vegetation like milfoil.

Clarity in Mille Lacs varies from year to year, depending on wind and the date of ice out, said Pereira, but in general it’s been getting better.

But clarity is not good for walleyes. The younger ones that hang out in shallower water go deeper to avoid the light, he said. But down in the depths, the pike hang out in the milfoil, ready to strike at any fish that wanders by.

Meanwhile, zebra mussels, which also make water clearer, and spiny water flea are taking layers out of the bottom of the food chain, which could be rippling through the entire ecosystem in unseen ways.

“You add that up — warming, clearing and invasives — and it’s not looking good,” said Venturelli. “We don’t know how this is going to play out.”

And then there is the human predator.

Every January, the DNR and the tribes with treaty rights sit down to decide how many walleyes can be harvested — the outcome of a series of court decisions that upheld a 19th-century treaty giving Indians the right to fish and hunt in northeast Minnesota. They base the “quota” on population estimates derived from gill netting samples and computer models.

This year the harvest was set at a paltry 40,000 pounds — 11,400 for the tribes, and the rest for anglers — far less than the half-million pounds from just a few years ago.

Critics of DNR’s management say that since the court decision, the state has had a dilemma. It had to try to make sure the state’s sport fishing quota, measured in pounds, lasts through the year. So regulations were set to allow anglers to keep only medium-sized fish — not the big, heavy ones.

But that left only big walleyes in the lake — big enough to spawn every year, and big enough to eat a lot of little walleyes.

There were times out in the boat, Fellegy said, when those hungry big walleyes would get caught repeatedly the same day, only to be thrown back again.

“The DNR was caught between a rock and a hard place,” he said. “How else do you stay under a quota?”

Plenty of babies

Today, there are as many opinions on how to fix Mille Lacs as there are fishing licenses in the state.

Gov. Mark Dayton announced last week that the DNR would start stocking the lake next spring. Some think that might help, if the fish are big enough.

“If you put 7- or 8-inch walleye in the lake, then they have less of a predation problem,” Fellegy said.

Biologists, including those at the DNR, say it’s not going to help. They say Mille Lacs has plenty of mature females producing plenty of little walleyes. “We know there are a lot there to produce young walleye,” Venturelli said.

Venturelli said a better strategy is to shut down fishing — as the DNR has done — and try to discover what’s going on in the ecosystem.

“Let’s err on the side of caution and protect what’s here,” he said. “And see if there is a way we can fix it.”

Fellegy said there’s not much left in the lake to work with, but there’s hope if people can hang on.

“This is a seven-year fix,” he said.

He still lives on Mille Lacs. But he’s moved his guiding service to Leech Lake.