Can catfish control nuisance bullheads? UND-North Dakota Game and Fish study aims to find out

Aug. 25—FORDVILLE DAM, N.D. — On a steamy Wednesday in late July — easily one of the hottest days of the summer to date — Tyler Bennett and Will Johnson launched their jonboat into Fordville Dam to pull trapnets and gillnets they'd set the previous day in the name of research.

Their goal: Catch black bullheads — as many as possible — on a day with sweltering heat and no wind.

Not surprisingly, they had the place to themselves.

Bennett, a UND master's degree student from Chicago, is overseeing the fieldwork portion of a collaborative research project between the North Dakota Game and Fish Department and UND to see if introducing channel catfish can help reduce bullhead numbers in lakes where the undesirable species is too abundant.

Johnson, a junior Fish and Wildlife major from Thief River Falls, is Bennett's field assistant for the project.

The target of this catfish stocking effort is Sweetbriar Dam, a 278-acre reservoir west of Mandan, North Dakota, where bullheads threaten to overtake species more desirable to anglers such as walleyes, bass and bluegills.

A sampling effort this past spring produced an estimated population of 250,000 bullheads in Sweetbriar Dam, Bennett says, and that's only accounting for bullheads longer than 180 millimeters, about 7 inches.

"We had a lot more of the smaller fish," he said. "It's pretty incredible, for how small the lake is."

In an effort to control those bullheads, the Game and Fish Department this past spring trapped 4,180 channel catfish from the Missouri River and Lake Oahe, where catfish are an underutilized species, and stocked them in Sweetbriar Dam.

As part of his fieldwork, Bennett is monitoring Sweetbriar to see how bullheads respond to that stocking. For research purposes, Fordville Dam, a similar-sized reservoir that also has an overabundance of bullheads, is a "reference" lake, Bennett says, essentially providing insights into a bullhead population that isn't controlled.

"It's not very often you get to introduce a novel species into a lake and have data pre and after to see the effects," Bennett said. "It's always after.

"Are they going to change their habitat use and foraging behaviors? Are catfish going to reduce that population?"

The nets at Fordville on this recent hot July day produced a variety of species, including walleyes, crappies, some very large pike and even a snapping turtle.

Bullheads weren't as abundant as hoped, but all of the bullheads Bennett and Johnson caught went back to the lab in UND's Starcher Hall, where the students would conduct diet analyses by cutting the fishes' stomachs open.

"Sometimes, it gets real smelly in (the lab)," Johnson said.

According to

Paul Bailey, South Central Fisheries District supervisor for the North Dakota Game and Fish Department in Bismarck,

the idea for the project dates back to the early 2000s, when the department stocked channel catfish from the Missouri River System into a handful of community fisheries.

Historically, crews would move smaller bluegills and perch from lakes with overabundant populations into the urban put-and-take fisheries, Bailey says, but during a series of dry years when those species were less abundant, Game and Fish decided to try stocking channel catfish.

Every spring, fisheries crews encounter catfish by the thousands during pike and walleye spawning operations on the Missouri River and Lake Oahe, he says. Turns out, the catfish were a hit among anglers, and in some urban fisheries with bullhead populations — such as the Game and Fish Department's Outdoor Wildlife Learning Site (OWLS) pond at the agency's Bismarck headquarters — bullhead numbers dropped.

"We stocked 150 catfish in (the OWLS pond) in the 2006-2007 time frame," Bailey said. During a test-netting survey the next spring, he said, "we hardly caught any bullheads whatsoever, but these catfish were still doing well in there.

"That was the first inkling I personally had that this may be a good method for two birds with one stone," Bailey said. "Providing good angling opportunity and also maybe eliminating bullheads that oftentimes aren't as desirable from an angling perspective."

Fast forward to 2016, when Game and Fish conducted a similar stocking effort at Braddock Dam in northern Emmons County. A department survey had found "very abundant" bullhead numbers in the 91-acre reservoir, Bailey says.

That's common in aging reservoirs as water quality declines and the habitat becomes less favorable for more desirable species, he said.

"The bullhead population in Braddock Dam seemed to be quite detrimental to the rest of the fishery there," Bailey said.

Game and Fish crews stocked about 850 adult channel catfish from Lake Oahe into Braddock Dam, Bailey said. By the next year, bullhead abundance had declined about 95%, he said. At the same time, the catfish from Oahe, which averaged 2 to 2 1/2 pounds when stocked, were showing up in Braddock Dam as 7- to 8-pound fish, he said.

"There was a lot of anecdotal information that with this abundant resource we have here in the Missouri River System with these adult catfish, it could be put to good use for reducing these nuisance bullhead populations," Bailey said. "And then these catfish themselves, it looks like they can provide some pretty good angling opportunity, and we did have some anglers start keying in on these catfish at Braddock Dam and really enjoying that resource."

Similar experiments in a "dozen or so" fisheries around the state, primarily in the Missouri River drainage, have produced similar results, Bailey says.

Despite the favorable early results, spring is an "enormously busy" time of year for fisheries crews, Bailey says, so the department wanted to glean more information before expanding the catfish stocking effort to other fisheries with bullhead issues.

That's where the collaboration with UND comes into play.

"We wanted to learn a little bit more about how we can most efficiently use these catfish to control bullhead populations and better understand the mechanisms of how it really works," Bailey said. "Sweetbriar provided a good opportunity to do that — a slightly larger reservoir than where we've utilized this technique in the past."

Adding Fordville as a reference lake gives credence to the study's ultimate findings, Bailey says. The expectation, he says, is that channel catfish will reduce bullhead numbers at Sweetbriar Dam. Bullhead numbers remaining high at Fordville would support that conclusion, but if numbers at Fordville also fall, then some other environmental factor could be at work, Bailey says.

Mark Kaemingk, an assistant professor of aquatic ecology at UND, worked with Bailey to develop the project. Kaemingk is also adviser to both Bennett and Johnson, his undergraduate assistant.

"I think Game and Fish was primarily interested in, 'Can they reduce black bullheads?'" Kaemingk said. "Maybe not necessarily the 'why,' but still curious. And so, we're trying to answer some of those mechanisms as to, if they do, how are they doing it? Is it through competition or is it through consumption?

"The original idea came from Paul, and then Tyler (Bennett) kind of ran with it and started coming up with a few other questions."

As part of the study, Bennett and Johnson also are sampling about a dozen other lakes — some with bullheads but no catfish, others with catfish that haven't reduced bullhead populations and others with catfish that have reduced bullhead numbers.

The lakes, which are scattered across the state, range from less than 100 acres all the way to Lake Darling, a 9,400-plus-acre fishery with a serious bullhead problem.

"We're looking at bullhead population demographics across all of these lakes," Bennett said.

The goal is to learn more about why stocking catfish as a means of bullhead control ultimately succeeds or fails, the Game and Fish Department's Bailey said. That finding remains a work in progress but early results are favorable.

"I guess I'm pretty optimistic we're going to gain some valuable information from this study that is going to help us, long term, reduce some of our nuisance bullhead populations and at the same time, create another fisheries benefit for our anglers," Bailey said.

In early August, Bennett and Johnson, with help from Game and Fish staff, sampled Sweetbriar to see what has happened since last spring's channel catfish stocking. They caught thousands of bullheads, Bennett says, including 1,600 in a single 4x6-foot trap net, but also a hefty 30 1/4 -inch catfish that weighed 14.2 pounds.

The catfish was probably "close to that size" when stocked last spring, Bennett says, "but it was clearly thriving in its new home." Catfish also had bullheads in their stomachs, he says.

The fieldwork portion of the study wraps up next spring, Bennett says. Aside from some water quality sampling, Bennett will spend most of his time next summer crunching data for his master's thesis.

That will provide a better picture of the study's ultimate success. For now, questions outnumber answers, Bennett says.

"I'll be writing a lot more — that's all I'll be doing," he said. "This is the fun part, what we're doing right now — play around with fish and drive boats."

Even on sweltering hot summer days.