Muskie research findings illuminate the specie's impact and future

Minnesota muskies have been known at times to devour extra-large prey, like the 18.9-inch white sucker that researchers retrieved this spring from the stomach of a 50-inch muskie on Shamineau Lake south of Motley.

Other surprises found in the fish diet study headed by Department of Natural Resources research scientist Brian Herwig have included a gull, muskrats and a couple of large bullheads. And in the stomach of a largemouth bass, Herwig's team found a baby snapping turtle.

Starting this year, the DNR is adding a second layer to its muskie research with a parallel project that will estimate populations in three lakes that muskies share with walleyes, northern pike and bass. Combining the data will provide a picture of not only what each species is eating but how much.

It's part of the DNR's plan to deepen muskie research before again writing a long-range muskie management plan. The last plan, which aimed to introduce muskies in new waters, was thwarted by age-old public sentiment that muskellunge destroy walleyes, crappies and other game fish.

"There's the perception that muskies eat everything in the lake," Herwig said. "But overall, their consumption can be much less than other species."

He said his research so far has shown that walleyes are not an important food source for muskies. "It's not zero, but it's close to that." Herwig said.

Minnesota Fisheries Chief Brad Parsons said the DNR remains committed to providing trophy opportunities for passionate muskie anglers. Later this year his staff will begin writing a new management plan, including a review of stocking efforts to deem what approaches are most efficient. Up for discussion again is whether muskies should be introduced to new lakes.

"Our goal is to manage with the best science," Parsons said. "We don't have any information that muskies are detrimental."

Shamineau Lake has been stocked for years with muskies and walleyes and isn't connected to other lakes or to a river. It's waters are too clear for it to be a prime walleye lake, but a research team led this spring by DNR's Tyler Ahrenstorff estimated that Shamineau holds 2,000 spawning sized adult walleyes.

There's nothing new about fish population estimates, but Ahrenstorrf's team broke new ground at the DNR this spring by conducting estimates for four different species at the same time, on the same lake. The effort required days of capturing muskies, walleyes, northern pikes and bass. Those fish were marked on the fin and released. In the second round of netting and electro-fishing, researchers noted how many fish of each species were recaptured. The adult fish population estimate for each species in the lake was based on the ratio of marked to unmarked fish.

"You have to get your hands on as many fish as you can," Ahrenstorff said. "We started April 7 and went for six weeks … it's a huge effort."

The preliminary results? There's approximately 150 muskellunge, 2,000 walleye, 3,700 northern pike, and 5,100 largemouth bass of spawning size in Shamineau Lake.

Eric Altena, DNR area fisheries manager in Little Falls, said early comparisons from Shamineau show that muskies are losing ground and walleyes have a little more abundance than previously thought. In a 2003 population estimate, the lake was holding an estimated 445 spawning-sized adult muskies. Because overall body conditions of those fish were on the skinny side, fisheries managers believe the ideal muskie population on Shamineau would be somewhere in the mid-200s. To get there, managers probably will tweak the stocking program, he said.

When the diet researchers complete their work this year, the two research teams will combine information and calculate yearly food intake for each species, also noting what types of prey they have in common.

In the study, DNR is using stable isotope analysis of certain tissues on the fish they catch to identify the chemical fingerprints of what each species has been eating. "It's like 'CSI Fisheries,' " Altena said. "It's great to get confirmation of what's eating what."

Herwig said the general patterns confirmed in other lakes so far show that perch and ciscoes are very important prey across the board. When ciscoes aren't available for muskies, they feed more heavily on bass and sunfish. Crappie predation is less common, and muskies will occasionally prey on northern pike, "but it's not super-duper common," Herwig said.

By combining the diet study with the population estimates, the scientists will learn, for instance, how many pounds of bluegills the muskie population in Shamineau is eating. Or, what percent of food that's in the lake are eaten by muskies vs. the percentage eaten by walleyes, northern pikes or bass. "Hopefully this study will give perspective," Ahrenstorff said.

But even if the answers reinforce existing research that muskies can live in balance with other fish populations, the DNR fisheries managers doubt studies will erase anti-muskie sentiment.

"It's like wolves. There's an emotion set with muskies," Altena said. "It's hard to get people around that emotion."