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ISLE, MINN. – Whatever else can be said of the court-ordered co-management by the Department of Natural Resources and eight Chippewa bands of Lake Mille Lacs fisheries, the giant body of water that extends some 18 miles across from this east-central Minnesota town of 800 possesses one of the most studied walleye populations in the world.
Those fish have increased in size and number sufficiently in recent years, DNR officials told a stakeholders group Tuesday evening at Appeldoorn's Sunset Bay Resort on Mille Lacs, that beginning in May a limited harvest of these fish is possible.
In the past three seasons, only catch-and-release open-water walleye fishing has been allowed on the big lake. Twice during those years, Mille Lacs walleye-fishing shutdowns — one planned, one a surprise — occurred to keep sport anglers from exceeding the hook-and-line harvest quota the state agreed to with the bands.
This year, DNR and tribal fisheries managers say 150,000 pounds of Mille Lacs walleyes can be safely taken from the lake. The share awarded anglers is 87,800 pounds, with an allowed 10 percent overage.
DNR fisheries chief Brad Parsons and Mille Lacs area fisheries supervisor Tom Heinrich told the Mille Lacs Fisheries Advisory Committee on Tuesday that about 700,000 walleyes 14 inches and longer now swim in Mille Lacs, up from 250,000 as recently as 2014, but significantly below the 1.1 million number from 2002.
A majority of the lake's current 14-inch-plus walleyes were hatched in 2013, a "year class'' that is old enough now to be "exploited.''
Yet these fish also must continue to be protected because they represent the bulk of the lake's mature, spawning walleyes, Parsons and Heinrich said. Therefore, the three open-water walleye-harvest options the DNR gave the advisory group Tuesday to consider would allow anglers only one walleye between 21 and 23 inches, and only during certain periods of the summer and possibly fall.
The proposed options are:
• A May 11-31 and fall Mille Lacs walleye harvest season. Otherwise, catch-and-release walleye fishing only. Chance of an unplanned walleye closure: 15 to 20 percent.
• A May 11-June 15 harvest season, with catch-and-release fishing otherwise and no fall harvest. Unplanned closure chance: 15 to 30 percent.
• A May 11 to June 15 harvest season, with a planned closure sometime in July and August perhaps lasting four weeks. Unplanned closure possibility: 10 to 20 percent.
Mille Lacs walleyes 21-23 inches long represent the upper size range of the 2013 year class.
As large as that year class is, the DNR likely wouldn't have allowed even a limited harvest of it if two of the lake's subsequent year classes — the 2015 and 2016 — didn't show promise they will survive in sufficient numbers to add eventually to the lake's walleye spawners.
"My guess is with the regulation options we're presenting, about 5 to 10 percent of the 2013 year class will be vulnerable to harvest this year,'' Heinrich said. "If we don't protect these fish by limiting the size that can be harvested and limiting also the times in summer and fall when they can be kept, we could impact these fish very quickly.''
Parsons noted Tuesday that the winter walleye bite on Mille Lacs has been good and that angler success is likely to continue this summer.
One reason is that the lake is home to relatively few yellow perch, a prime walleye forage fish. The decline is the result, perhaps, of a corresponding falloff of the lake's zooplankton.
Zooplankton, generally, are tiny, even microscopic animals such as copepods that newly hatched walleyes and other fish feed on.
"We suspect the zooplankton decline is related to the arrival of zebra mussels and spiny waterfleas in Mille Lacs,'' Heinrich said. "Overall, since their arrival, there's been a decline in productivity in the lake, which might make it difficult to reach the really high Mille Lacs walleye populations we once had.''
Heinrich stressed, however, that Mille Lacs zebra mussels have declined to about half of their peak abundance of a few years ago, and that each lake responds differently to the arrival of invasive species.
Lake Erie, for example, changed similarly to Mille Lacs when zebra mussels were introduced there, with walleyes falling off and smallmouth bass increasing. Wisconsin's Lake Winnebago, by contrast, Heinrich said, maintained its walleyes under similar circumstances.
"We know zebra mussels reduce a lake's carrying capacity,'' Heinrich said. "But by how much, we're not sure. It's probably very lake-dependent.''
Advisory committee members told Parsons, Heinrich and other DNR fisheries staff Tuesday that whichever harvest option is chosen, most important is that Mille Lacs walleye fishing isn't shut down to harvest or at least catch-and-release angling during the open-water season.
Such shutdowns are business killers, the group said.
The DNR will announce a Mille Lacs walleye harvest decision next month.
Dennis Anderson • danderson@startribune.com
