Managing fish populations in Ackley Lake

Tiger muskies, introduced to eat suckers, also eat trout
Melody Montgomery Special To The News-argus
Saturday, February 23, 2019
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Razor-sharp teeth fill the mouth of a tiger muskie, one reason why they are an effective predator fish.

Photo courtesy of FWP

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A total of 54 ice fishers participated in the Ackley Lake ice-fishing derby last month. Shown here are warming huts scattered across the reservoir.

Photo courtesy of Nancy Epkes

Just over three years ago, in 2015, a total of 4,000 carnivorous fish - tiger muskies - were introduced into Ackley Lake, a reservoir in Central Montana located near Hobson. These fish are a sterile hybrid, a cross between northern pike and muskellunge, both of which are predacious fish.

The reason behind introducing tiger muskies into Ackley Lake is to control the population of white suckerfish which infested the lake. Suckerfish are thought of as throwaway fish, undesirable for human consumption. The tiger muskies, on the other hand, are edible.

So basically the tiger muskies’ job in Ackley Lake is to eat the suckerfish, and people can in turn eat the tiger muskies -- that is, once the tiger muskies reach 40 inches in length. A similar strategy began taking place in Deadman’s Basin Reservoir beginning in the 1990s, so there was record of this being successful.

“We are seeing anglers come to Ackley specifically targeting tiger muskie,” said Fish, Wildlife and Parks Fisheries Biologist Clint Smith, who has not yet recorded 40-inch tiger muskies, but who has seen tiger muskies in the mid-30-inch range. Smith says the fish are doing their job – growing and eating suckers.

However, tiger muskies also eat trout.

While anglers may be waiting for the tiger muskies to reach the required length, concerns remain about the bite they are taking out of the trout population.

“Anglers have been expressing concerns about the trout catch rate and have even started going other places to catch trout,” said Smith.

Still, the net result, with more fishing for tiger muskies and fewer fishing for trout, is probably not much of a change in overall angler use, Smith said.

“Ackley Lake caretaker Roger Epkes, who’s out there quite a bit, has told me he hasn’t noticed much change in total use,” said Smith.

Regardless of what type of fish anglers seek, a healthy trout population is important to the lake and FWP. On the other hand, in order for FWP to define a new process, there must be clear data to back it up.

“[Given their recent introduction], we currently do not have trend data, but we plan to set traps along the shore this spring to give us reference numbers,” said Smith.

These numbers will help determine their course of action to keep the trout population healthy.

“As part of our management moving forward, I hope to include more creel surveys, with time and money, of course, which will give us a better indication of angler use and satisfaction,” added Smith.

Results from the Ackley Lake Ice-Fishing Derby

The Ackley Lake Club hosted an ice-fishing derby on Jan.


A total of just six trout were caught among five anglers, with one individual catching two and the other four individuals catching one trout each. Chad Chord of Hilger caught two trout, and catching one each were Jake Evans of Laurel, Tim Barta of Fort Shaw, Garn Wanner of Great Falls and Mike Woods of Hobson.

According to Lewis Reedy, a member of the Ackley Lake Club, this number of trout is rather low, but it was still a nice day.

“It was a beautiful day. MotherNature was saying, ‘Yes, I am going to provide you with a nice day, but I am not going to provide you with fish,’” said Reedy.

“Considering there were 54 entrants, that means only one in 11 entrants caught a fish,” Reedy added.

FWP’s Smith agreed these numbers are low, but they are not necessarily indicative of the number of trout in the lake.

“That is a very low catch rate, but I did talk to the warden in the area who said it had not been as slow all winter, so it was also not a good fishing day,” said Smith. “On the other hand, trend indicators do show the trout number is down, which is something we are keeping an eye on and trying to address.”

Montana FWP is considering three strategies to help improve the trout numbers:

Strategy 1: Stock more trout

To balance the trout loss due to the tiger muskie, FWP stocked a total of 55,000 rainbow trout, 4-inches in length, in Ackley Lake last year, mostly during May, and are considering stocking even more trout this year.

Still, considering the length of the trout stocked, they could be considered a nice-sized snack for the tiger muskies and “highly susceptible to predation,” said Smith.

It also takes the trout a year or more to grow to 8–10 inches, when they become available to anglers, Smith said, explaining the lag time accompanying stocking trout in the lake.

Of 55,000 trout stocked last spring that survived predation, the remaining trout will start to become available to anglers this coming spring, and the different strains stocked become available at different times, Smith said. Trout have an average lifespan of three to five years, Smith added.

Strategy 2: Modify regulations

The second strategy Smith discussed is to modify the regulations, which also takes time. For example, regulations could be changed to reduce the harvest of trout, or alternatively, to increase the harvest of tiger muskies. For example, presently tiger muskies must be at least 40-inches long to be harvested, and only one can be harvested per day at this length. This could be changed to somewhere around 30 to 36 inches, and anglers could be allowed to take home a couple of tiger muskies in a day.

“If changing these regulations was deemed necessary, the change would occur in the 2020 license year. The regulatory change is an eight-month process,” said Smith.

Strategy 3: Manual removal

A third option Smith discussed is having FWP go in and manually remove tiger muskies. However, FWP remains cautious about taking this route because it could potentially shift the problem back to what it had been when the tiger muskies were added – a sucker infestation.

“It’s a difficult balance. We want those tiger muskies to complete their job of suppressing suckers. We do not want the pendulum to swing too much back to where the suckers are again being caught,” said Smith. “We also want a healthy trout population and will have to walk that tightrope.”

Tiger Muskie Tournament planned

The Ackley Lake Club will host another fishing contest this summer – their first annual Tiger Muskies Tournament, which Montana FWP has approved for June 22.

“We’ve heard angler reports of tiger muskies over 40 inches,” said Smith.

Net proceeds from the tournament entry fees will go to the Ackley Lake Club, which installed eight new overflow campsites last year and is now working on additional improvements to facilities, Reedy said.

The contest is expected to draw anglers from around the state.



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