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DNR study reveals what muskies eat

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DNR study reveals what muskies eat
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Anglers and lakeshore owners often wonder what muskellunge eat and how this top predator affects other fish populations once it has been introduced into a new body of water.

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Answers to those questions can be found in studies conducted by the Minnesota and Wisconsin departments of natural resources.

"Today, we know more about the muskie's diet and its impact on other fish populations than ever before," said Tim Goeman, Minnesota Department of Natural Resources (DNR) regional fisheries manager. "And that knowledge indicates muskies do not have a detrimental effect on other fish species when stocked at relatively low levels in water bodies with the right characteristics."

The Minnesota DNR conducted an in-depth examination of fish population impacts in 2007. That's when Mike Knapp, a DNR fisheries biologist, and other fisheries staff did an extensive analysis of fish populations in 41 lakes that had been stocked with the Leech Lake strain of muskellunge. Knapp, who co-authored a report on this work, said the analysis across all 41 lakes and smaller groups of similar lakes did not show a significant decrease in any fish species after muskellunge had been stocked.

"If muskie stocking resulted in a negative impact on other fish populations, we would have seen a pattern emerge," said Knapp. "But that didn't happen. Instead, we found great variability. When looking at individual species in individual lakes, our nets caught significantly more fish in 16 cases and significantly fewer fish in nine cases. Our nets caught essentially the same number of fish in the other 194 cases. The lack of consistent negative changes suggests muskie and other species generally coexist quite well."

In Minnesota, muskellunge typically prey on whitefish, tullibee, suckers, redhorse and yellow perch. Knapp said study findings related to these prey items were:

n No significant population changes (increases or decreases) were detected for tullibee, white sucker, or yellow perch across the 41 lakes.

n Lakes that did not contain tullibee (a preferred prey species) did not have negative fish population impacts after muskellunge had been stocked.

Knapp said the study findings are in line with a Wisconsin DNR study conducted from 1991 to 1994. That study examined the stomach contents of 1,092 muskellunge from about nine to 46 inches in length. Wisconsin researchers found 31 different species of fish in the stomachs of muskellunge, primarily perch and white sucker.

Tom Burri, a Minnesota DNR biologist who worked on this study while previously employed in Wisconsin, said the diet study was enlightening.

"We found only five walleye in the stomachs of 1,092 muskellunge," said Burri. "Muskie actually ate more muskie than walleye. We found six muskies inside of muskies."

Burri said the Wisconsin diet study indicated that 98 percent of a muskie's diet, by volume, was comprised of fish. The other two percent, he said, included crayfish, insects, mudpuppies, tadpoles and one mouse. Walleye, bass and northern pike ranked low in the muskie diet.

"When we used electro-fishing boats to sample fish populations at night, we often found walleye and muskie in close proximity yet the muskellunge stomachs rarely contained walleye," said Burri.

He said this information suggests that walleyes are either not a preferred species by muskellunge or walleyes are adept at avoiding predation. The latter may be related to the walleye's eye, which is designed for excellent night vision.

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