Anderson: DNR fisheries chief addresses walleyes on Mille Lacs

New Minnesota DNR fisheries chief Don Pereira tries to answer the unanswerable: What's wrong with Mille Lacs walleyes?

Q: What's the status of Mille Lacs walleyes?

A: We have an abundance of spawning females. But there's an elevated mortality of young walleyes, and we're not sure why. Walleyes are in the lake in good numbers after the spawn, but they're not surviving in sufficient numbers as yearlings and 2-year-olds. We haven't had a notable year class since 2008, and good year classes before then were too infrequent.

Q: Reasons?

A: Our leading hypothesis is that they are probably dying from elevated predation. Mille Lacs became clearer and clearer beginning in the late 1990s. At the same time, we detected that walleyes were moving offshore at a much smaller size than they historically have. We think that the clearer water, and the predation that it might have encouraged, might have been the reason. Meanwhile, we know that smallmouth bass in the lake have increased dramatically, as have larger walleyes and northern pike, all of which prey at times on small walleyes. That said, we're unsure exactly how these things work together.

Q: When might you figure it out?

A: We had a good predator diet study this year. But fish feed differently, year by year. We'll get an initial look at which predators are consuming young walleye this year, but will certainly firm up this work with additional years of predator diet sampling.

A: It's possible. But I want to stress that Mille Lacs appears to be unique in that regard. We've had similar protective slots on Rainy Lake for 20 years and on Winnie for 10 years. We're still seeing good reproduction on those lakes, without loss of year classes as the fish mature. But regarding Mille Lacs, the mistake we might have made was focusing fishing mortality on walleyes 15-18 inches long. We now know a sustainable fishery should be exploited across a broad age and size range.

Q: On Mille Lacs, harvest quotas for anglers and Chippewa netters are set by poundage. So if you allow more big walleyes to be kept, quotas will be reached more quickly.

A: True. But first we need to focus on getting the system recovered. As we do that, or when we do, we'll have to spread harvest across a broader size of fish. How the bands accomplish that, we don't know. We don't know how we'll do it, either. Again, there's a degree of speculation in what I'm saying, because we haven't completed all of our research.

Q: Do you envision angler regulations changing on Mille Lacs this year, from an 18- to 20-inch harvest slot, with one allowed over 28 inches, and a two-fish bag?

A: We hope to keep it where it is, but nothing is on the table right now. It appears the bite will be slow, because yellow perch are abundant for forage. We will meet with the Mille Lacs advisory committee and discuss it.

A: Fisheries science is complex. Sometimes it's good to have a fresh look. The people at Michigan State, for instance, have studied our Mille Lacs model and have given us feedback. Another expert we're working with is highly knowledgeable in walleye mortality. Another knows zebra mussels and their relation to clearer water, increased plant growth and pike predation. I'm excited about the intellectual power we're bringing to the issue.

Q: What have you told the Chippewa about your assessment of the lake and your plans?

A: We've kept them informed. They're supportive, and and the Federal court is clear that the State can only object to tribal interests for reasons of conservation or health and human safety.

Q: Is there hope for a walleye rebound?

A: I think so. Most vexing are the ecological changes. There's just a lot going on in that lake. Additionally, it was a sort of a perfect storm when the tribal fishery began at the same time the lake began changing.

A: I don't want to speculate about that. We will do everything we can to sustain resorts and area businesses while we figure this thing out. The state tourism people will help by stressing the diversity of attractions in the area while we work on the walleye issue.

Q: Talk about northern pike.

A: Milfoil has expanded dramatically in the lake, out to 18-foot depths. We know pike like plants. Does the plant expansion explain why pike have increased? If we think it does, we may promote the lake's pike fishery.

Q: Are smallmouth bass eating the small walleyes?

A: We won't prosecute a particular fish until we find out it's a problem. There's not a lot of literature that says smallies prey disproportionately on walleyes. Though July, their diet in Mille Lacs is mostly on crayfish.

A: We're taking money from other projects. We're pulling staff from throughout the state. It's a huge problem and it's worthy of a lot of attention.

Q: Finally, do muskies play a role?

A: The lake's muskies are low-density. We manage muskies statewide for one fish per 4 acres. On Mille Lacs, it's one fish per 50 acres. If you're a muskie angler, you won't catch a lot of fish in Mille Lacs. But if you do, chances are good it's longer than 50 inches.

Dennis Anderson danderson@startribune.com