Studies reveal what muskies eat, impacts other fish populations

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Studies reveal what muskies eat, impacts other fish populations
(Released August 26, 2010)



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.


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:

No significant population changes (increases or decreases) were detected for tullibee, white sucker, or yellow perch across the 41 lakes.
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.Burri said despite strong walleye populations in some of the Wisconsin study lakes, walleye were not an important food for muskellunge.

“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.

“When walleye and muskie are in shallow water at night the walleye’s night vision might help them avoid predation,” Burri said.

Goeman said study findings are particularly relevant right now because the Minnesota DNR is considering introducing muskie into five new water bodies starting in 2011. Lakes under consideration for muskie stocking include Roosevelt in Crow Wing and Cass counties, Upper South Long and Lower South Long in Crow Wing County, Tetonka in Le Sueur County, and the Sauk River chain in Stearns County.

“The proposals reflect a growing interest in muskie fishing, as well as confidence that introducing muskie into these waters will not have detrimental effect on other fish populations,” Goeman said.

The DNR will hold six public input meetings around the state on Thursday, Sept. 2, for people to comment on the stocking proposals. Meeting times, locations and other information is available at mndnr.gov/muskie.

[dakids]

On waconia my grandpa used to catch bullheads by the bucket full before muskies.  Now you can't catch one to save your life.  I hate the bullhead.  Stepped on one as a kid.

[DDSBYDAY]

    Very interesting article.  Thanks for sharing.  I primarily fish Roosevelt in Cass county so my lake is on the list.   I was not sure I was for stocking  muskies  but this lake is hard to fish (my personal theory is it is so full of baitfish), so maybe it would be a good thing.