Bits & Pieces: Muskie Impacts, Walleye Tournaments, & Bass Learning

Field Research: Impacts of Muskies on Other Gamefish

When state agencies consider introducing muskies to a lake, they often receive questions and objections from local anglers, guides, and lakeshore property owners about how adding this large and predatory species will impact their fishing for other species. Even where muskies have coexisted with walleyes, pike, and bass for centuries, questions arise about muskie predation when populations of other fish decline. A look down their throat is indeed intimidating. In Minnesota, legislators even proposed to suspend Department of Natural Resources (DNR) stocking plans and allow counties to provide be involved in the decision process, despite most previous studies indicating minimal effects on native species.

To address such questions, a team of from the University of Minnesota and the Minnesota Department of Natural Resources examined the diets of muskies, largemouth bass, northern pike, and walleyes living in eight lakes in Minnesota.* Some study lakes contain populations of cisco (tullibee), a common muskie prey; others not. They examined gut contents of the four predatory species and conducted genetic sequencing to identify food items that were too digested for visual identification. The sampling technique, called gastric lavage, involves injecting water into the fish’s gut, which flushes food items into a container, leaving the fish none the worse except for its lost meal.

A total of 29 prey types were found in the four predatory species, mostly familiar prey such as perch, centrarchid panfish, and crayfish; but also ring-bill gull, mallard duck, and muskrat. Even in lakes containing cisco, muskies relied primarily on yellow perch, black crappie, sunfish, and bullheads, with bass and white suckers as well. With cisco absent, muskies ate more pike, followed by sunfish, bass, crappie, and bullheads. One 47.4-inch muskie had recently consumed 101 other fish: 2 bullheads, 1 large white sucker, and 97 perch.

Diet analysis of the four species found the most overlap occurred between walleyes and pike, as both relied heavily on perch, with sunfish and crappies also important. Diets of muskies were more diverse, what lead researcher Kamden Glade referred to as “unspecialized foraging.” Bass forage, on the other hand, was heavily invertebrate, especially crayfish, with panfish also important. In some lakes, muskies ate substantial numbers of pike and bass, but would have no significant effect on the abundance of those species.

They concluded that the ability and willingness of muskies to consume a broad range of prey, compared to other piscivores, limited any potential negative influences on walleye, pike, or bass populations. Contrary to negative impacts, they suggest that muskies’ foraging may lead to increased stability of lake food webs.

-Steve Quinn

*Glade, K. C., B. R Herwig, T. D. Ahrenstorff, J. R. Reed, and A. W. Hafs. 2023. Diet patterns and niche overlap of muskellunge and co-occurring piscivores in Minnesota lakes. N. Am. J. Fish Mgmt. 46:656-676.

Fishery Management: Virtual Walleye Tournaments Provide Fishery Data

Researchers with the Iowa Department of Natural Resources and Angler’s Atlas conducted smartphone app-based virtual walleye fishing tournaments as a citizen science endeavor to compare angler catches with DNR fishery surveys. Statewide tournaments were conducted May-June of 2022 and 2023, and the overlap between survey data and angler catches showed promising results. The study provides information on fishing pressure and catch rates across multiple water bodies, and walleye population size structure. Angler identities and their specific catch locations remain anonymous, so secret spots stay secret.

In 2022, 70 anglers caught fish from 41 different water bodies during 551 different fishing trips. A total of 2,074 walleye and sauger catches were reported during 1,795 hours of fishing, for an average catch rate of 1.4 fish/hour. In 2023, 88 anglers caught fish from 75 water bodies during the course of 732 fishing trips. A total of 2,782 catches were recorded during 2,596 hours of fishing, for an average catch rate of 1.1 fish/hour. Across the two years, Iowa’s Big Creek Lake, Brushy Creek Lake, Clear Lake, Rathbun Lake, and Spirit Lake have been popular with anglers and provided high catch rates. Additional anglers fished a variety of Mississippi River pools in 2023, increasing the data reported from that excellent walleye fishery.

 The initial success of this endeavor encouraged researchers to expand this project across a broader geographical range, leading to the 2024 Midwest Walleye Challenge (anglersatlas.com/events). These efforts to learn more about regional walleye populations and develop new monitoring tools for fishery scientists are being supported by the U.S. Fish & Wildlife Service, as well as fish and wildlife agencies across the US and Canada. Anglers can sign up for, and compete in, state-based events in Illinois, Indiana, Iowa, Nebraska, and Wisconsin. Prizes will be awarded for biggest fish in each state, hard-luck prizes for anglers who record trips without catching any fish, and random-draw prizes from each fish entered (so enter all the fish you catch). Anglers from other states can also enter and compete for the Grand Prizes from the Midwest Walleye Challenge.

Walleye anglers interested in improving walleye fishing through stocking assessments and advancing fishery management practices can help to accomplish these goals by participating in the Midwest Walleye Challenge.

-Jeff Kopaska

From the Archives: Live and Learn

Unpleasant experiences and danger teach fish more rapidly than routine rewards. Furthermore, once a habit or behavior pattern is learned, it seems hard for a fish to unlearn it. Dr. Robert J. Edwards fed frogs to several black bass. Then the bass were fed a species of toad known to have an unpleasant taste. The bass struck once and spit them. Then they would not strike the unpalatable toads or the edible frogs.*

The bass learned an avoidance response from the unpleasant experience. The bass were, however, apparently unable to see the difference between frogs and toads. The fish learned to avoid the shape and behavior of both animals.

Studies show that some fish remember lessons for months or years, while others forget within days or minutes. How long an experience is remembered seems dependent on how clearly and directly a fish associates an event with a reward (food) or punish­ment (pain or danger). A bass may learn to avoid a lure of a particular shape, action, or color if the fish has carefully observed it before striking. Another bass may strike without seeing the lure in detail and fail to associate his predicament with a specific bait.

-Ralph Manns

*Edwards, R. J. 1980. The ecology and geographic variation of the Guadalupe bass, Micropterus treculi, Ph.D. Dissertation. The Univ. of Texas, Austin.

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