Anderson: Mille Lacs study of walleye population on thin ice

  • Article by: DENNIS ANDERSON , Star Tribune
  • Updated: May 17, 2013 - 12:23 AM

Because of the late ice this spring, a DNR study of the walleye population has tagged only 6,000 fish.

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Lake Mille Lacs still was covered in ice in early May. This photo was taken near Garrison on the northwest side of the lake.

Photo: DNR photo by Tom Landwehr, Dml -

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So far this spring, little has gone as planned on Mille Lacs, starting with the late ice-out, which — if it didn’t occur Thursday afternoon or evening — likely will happen Friday.

In addition to millions of dollars of revenue lost by resorts, bait shops and other businesses so far this fishing season, lost — or at least diminished — in the delayed transition from hard water to soft has been a long-planned assessment of the lake’s walleye population by the Department of Natural Resources.

Lost as well to the eight bands of Chippewa that net and spear the lake in spring is anything near their quota of walleyes, which was 72,250 pounds this year.

As of Wednesday, the bands had collected only 13,500 pounds. And most tribal netting and spearing is likely complete for the spring because the lake’s walleyes are done, or nearly done, spawning.

How could spawning be complete when most of the lake has been ice-covered until the last day or so?

Easy: The fish began their reproduction process under the ice, triggered by the length of the day, if not by water temperature, which this month generally has remained below 40 degrees Fahrenheit throughout much of Mille Lacs.

“But when you get a sunny day and have a little open water along the shore, those areas can warm up into the 40s,” said Rick Bruesewitz, DNR area fisheries supervisor. “And fish can move in to spawn.”

Unfortunately for the DNR, its electroshocking and netting crews couldn’t reach the same shoreline waters in their attempts to assess the lake’s walleye population by tagging thousands of fish.

Recent DNR studies have suggested Mille Lacs walleyes are at a 40-year low, and fisheries managers had hoped to refine that population estimate, while also determining which walleyes are particularly vulnerable to sport fishing.

To that end, the DNR had planned for its crews to catch and tag 20,000 walleyes during the spawn. Some would be corralled in hoop nets placed in the lake’s shallows. Others would be temporarily stunned and floated to the surface by DNR electrofishing crews.

“But we couldn’t get our crews into the small areas along the lake that were free of ice,” Bruesewitz said.

Consequently, as of Thursday, perhaps only 6,000 walleyes had been caught and tagged. That relatively low number, Bruesewitz said, will create “confidence levels in our population estimate that are much wider than we would like to see.”

One option is to redo the study next spring. Another is to redouble the agency’s plan in a couple of weeks to capture walleyes after they have dispersed throughout the lake.

This second effort would create a ratio of tagged walleyes to untagged walleyes, which would help form the basis of a new walleye population estimate.

But because only about 6,000 walleyes are wearing tags, fisheries technicians would have to capture as many as 15,000 fish in the second go-round to get a reliable handle on the lake’s walleye numbers.

Capturing that many walleyes in the open lake could be problematic, Bruesewitz said, because DNR technicians use gill nets in the second attempt, not hoop nets, and the former pose a greater threat to caught fish.

Additionally, the staffing required to catch that many walleyes, considering that DNR crews leave gill nets in the water only 20 minutes or so at a time, would be considerable.

The tagged walleyes also were intended to help the DNR further understand the distribution of male and female fish in anglers’ catches.

Mille Lacs anglers who catch tagged walleyes this spring and summer are being asked to return the tags to the DNR, or at least inform the agency of tag numbers, so the sex, size and other information of caught fish can be recorded.

The fact that only 6,000 or so tagged walleyes are swimming in Mille Lacs, compared to the planned 20,000, will make the study less complete than planned.

How valuable are the two Mille Lacs projects?

“Extremely valuable,” Bruesewitz said. “If fishing is really good this summer, and we get a sufficient number of tags returned, we can see which fish anglers are catching. And if the recapture [by gill net] goes well, we could get a reasonable look at the lake’s overall walleye population.”

Anglers who turn in tags, or report them, receive a fishing lure from the DNR as a reward.

“I’ve been trapping fish on this lake since 1991,” Bruesewitz said, “and we’ve done these types of studies before. But we’re already nine days past the latest date we’ve ever tried to net Mille Lacs walleyes.”

 

Dennis Anderson danderson@startribune.com

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