St. Paul — The headlines in 2018 weren’t subtle. They filled newspapers, online news sites, and other media outlets.

“Minnesota Legislature declares war on muskies: The proposed anti-muskie law would blow up the long-range muskie management plan of the DNR.”

Another: “Minnesota muskies: exciting catch or monster nuisance?”

One of the largest and most elusive fish in Minnesota, the muskie – or muskellunge – is an apex predator extraordinaire with a seemingly insatiable appetite. But in 2018, the hunter became the hunted.

Blood was in the water. Some politicians, guides, lake association members and even regular anglers – most devotees to the state fish, the revered walleye – wanted to, more or less, kill state muskie management. Their collective belief was that muskies adversely were affecting resident fish populations, especially walleye populations, in waters where they were managed and stocked by the Minnesota DNR. That, despite a stubborn body of scientific evidence suggesting otherwise.

“Muskies have a polarizing history in Minnesota,” said Brian Herwig, Minnesota DNR fisheries research scientist in Bemidji.

“Minnesota is a walleye state, full of walleye anglers. While the original bill in the Legislature didn’t go anywhere, there was clearly a need for some additional research and new data on the muskie question.”

Herwig said interested stakeholders wanted answers to two questions. One: What are muskies eating in Minnesota waters? Two: How do muskie diets compare with those of walleyes, northern pike, and largemouth bass – popular sportfish hailed by Minnesota anglers?

The field work to answer those questions began in 2019 as part of a multi-year study. One part of the project analyzed the stomach contents of the four fish species in several Minnesota lakes.

The second part, aided by researchers from the University of St. Thomas and Bemidji State University, used so-called stable isotope analysis, a technique that utilizes tissue samples to determine a fish’s diet. The two approaches complement each other by providing a broader, more detailed picture of what they eat.

Based on previous research that showed the diet of muskies relied heavily on ciscoes, the study design, Herwig said, fell into four categories: lakes that had both muskies and cisco; lakes with muskies only; lakes with only ciscoes, and lakes without muskies and ciscoes. Roughly 20 lakes were sampled for the project.

Field work

None of the dietary analysis could be conducted without first catching the fish – a difficult, time-consuming endeavor. Enter Kamden Glade, who in 2019 was a student at Bemidji State. For about 50 days a year for four years, Glade and his team were on the water, collecting fish.

While some fish in the study were netted and even caught by angling, most were subdued and caught by electrofishing, a common, nonlethal fisheries practice in which a generator produces an electric field in the water to temporarily stun fish.

“We did the electrofishing at night, and what we quickly learned was that muskies were much harder to stun and capture than smaller fish,” said Glade, who is now a Minnesota DNR Fisheries specialist in Tower. “They’re bigger fish and powerful swimmers. They detected the current farther away.”

A change in tactics was in order. The team decided to use spotlights to locate muskies – no easy task, because muskies are “low-density” fish – typically in shallow water.

“We then maneuvered the boat directly over the top of the fish as much as possible before flipping the switch (on the generator),” Glade said. “Then we had to net the muskie before it recovered and swam off. With bigger fish, it got pretty interesting.”

In four years, Glade said, 4,864 fish (muskies, largemouth bass, walleyes, and northern pike) were caught. The stomach contents were collected and analyzed by inducing vomiting. With the help of a 12-volt battery, bilge pump, and clear poly tubing, lake water was pumped into a fish’s stomach, creating back pressure and forcing a fish’s “prey items” out. When handling the fish, special electricity-emitting gloves were used to keep the fish immobilized. “They worked pretty well,” Glade said.

Colorful contents

Over four years, the stomach contents of 326 muskies were sampled (roughly 50% of captured muskies didn’t have anything in their stomachs). The sizes ranged from 11.2 inches to 54.9 inches.

Some of the findings made for colorful anecdotes. For example, one muskie’s carnivorous frenzy took glutenous binge-eating to whole new level. The vomit of a 47-plus-inch fish captured in Lake Miltona in Douglas County showed it had eaten 101 individual fish, 97 of which were yellow perch. The others: one bluegill, a sucker, and two bullheads.

“That fish was a complete outlier,” Glade said.

The muskie menu included non-fish prey, too. Some consumed muskrats, while others consumed birds, including at least one coot, a duck, and a gull. Another interesting item: The largest muskie in the study was 54.9 inches long and was caught twice – in May 2021 and August 2021. Six muskies were found to have eaten other muskies.

The digested fish remains of some muskies needed genetic analysis to determine the species. Some prey fish were hard to extract.

“We had to use kitchen tongs to get some larger suckers out,” said Glade, laughing. “I think we picked up a pair at Target.”

Muskie diet

Herwig said the study’s results show Minnesota muskies have a varied diet, consuming a broad range of prey species compared with walleyes, northern pike, and largemouth bass, which, Herwig said, “leads to low levels of diet overlap.”

Muskies, Herwig said, while consuming some shared prey species such as sunfish and perch, also eat bigger species, including suckers, northern pike, and bullheads.

“Muskies are able to exploit larger-bodied species,” Herwig said. “That gives them a unique niche in the food web relative to the other predator fish we sampled.”

According to the research, only three walleyes were found in sampled stomach contents of muskies.

“In our study, in our direct examination of 326 muskie stomachs collected in various seasons in eight different lakes, we observed just three walleyes in stomachs. This means they were found in less than 1% of all the muskies we examined,” said Herwig, which is consistent with two previous DNR studies that found muskie stocking and management had not adversely affected walleye populations. “Similarly, in the stable isotope data, we found no evidence that walleyes were an important component of muskie diets.”

Overall, Herwig said, the research hasn’t found “any evidence that muskies disproportionately eat walleyes, as some anglers claim.

“Northern pike actually ate the most walleyes,” he said. “Seventeen out of 741 northern pike stomachs from 12 different lakes had a walleye in it, but that still only amounts to 2%.”

Future management

Herwig said DNR Fisheries is working on a new long-range muskie plan, which should be released at some point next year and will likely run for 15 years.

The research results will be included in it. He said the agency is currently focused on improving how it manages the state’s existing muskie lakes. In the near future, Herwig said, the agency will offer the public an online survey regarding muskie fishing and muskie management. The results will be incorporated into the long-term plan.

“We’re looking at getting some public feedback on how we’re going,” said Herwig, adding that the agency may consider some adjustments to muskie stocking, perhaps releasing more yearling muskies. “Some studies suggest it increases survival,” he said.

Findings from the new research likely won’t prompt DNR managers to increase the number of muskie lakes the agency stocks and manages in the near future, DNR fisheries officials say. That could change after the long-term management plan is completed.

“I don’t think there’s a strong appetite for new introductions right now,” one official said.

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Minnesota Muskie Facts

• Muskies are native to Rainy Lake and the Rainy River, as well as from the upper Mississippi River drainages to the lower Mississippi River to Lake Pepin.

• The current Minnesota catch-and-release muskie record is 58.25 inches.

• On average, a 50-inch muskie is about 17 years old.

• The Minnesota DNR stocks 48 waters with pure Leech Lake strain muskies, and 11 waters near the Twin Cities metro area with tiger (hybrid) muskies.

• A 2018 survey of Minnesota anglers showed 11% of anglers actively fished for muskies, and 29% were likely to want to fish for them in the future.

• Each spring, DNR Fisheries staffers conduct sampling to monitor the muskie population. Surveys are done primarily where muskies are stocked. Population status, size structure, sex ratio, and growth trends are tracked.