Hyprid fish

Chance Kirkeeng, a fisheries biologist for the Wyoming Game and Fish Department, holds a 24.6-inch tiger muskellunge that was collected this spring from the Upper North Crow Reservoir in Curt Gowdy State Park between Laramie and Cheyenne.

LARAMIE — A hybrid species of carnivorous fish introduced into the Upper North Crow Reservoir in Curt Gowdy State Park several years ago is getting big enough to give anglers a good fight.

Tiger muskellunge, also known as tiger muskies, are the sterile hybrid offspring of muskellunge and northern pike.

In 2015, the Wyoming Game and Fish Department put about 650 tiger muskies into the North Crow for the purpose of feeding on longnose suckers and white suckers. Those two species of native fish compete for resources with trout, which had been stocked in the reservoir since 2006 but weren’t thriving.

“[The suckers] were tying up a lot of the food resource, so we weren’t seeing a lot of fish growth where we’d expected,” said Bobby Compton, Laramie Region fisheries supervisor for the Wyoming Game and Fish Department. “We’ve been actively trying to control and remove those suckers.”

While suckers are native in Wyoming, they’re typically found in rivers. When introduced into manmade reservoirs, their numbers can expand rapidly and at the expense of other species, Compton said. Statewide, the sucker population is healthy.

“The softer habitat allows them to explode,” he said.

Fisheries biologists tried removing suckers with nets for several years but didn’t make much headway, so they turned to tiger muskies.

The fish are raised at the Dan Speas Fish Hatchery in Casper for the sole purpose of controlling other fish species, since that’s the entirety of their diet. Because they’re sterile, they won’t start reproducing and become a problem themselves. Instead, they’ll eventually die out as scientists decide their presence is no longer needed.

“It’s a tool that biologists can use because we can control their numbers,” Compton said.

Game and Fish added tiger muskies in 2016 and 2017 for a total of 6,650 over three years. While they were small at first, they’ve been growing and feeding ever since.

Compton said biologists have caught muskies more than 20 inches long during recent sampling efforts. They’ve also seen a decrease in the number of suckers pulled in. During the past year, they’ve received reports from anglers who have spied the fish in the reservoir.

“When we have a lake full of large adults, that’s when we really expect to see a big decline in the sucker population,” he said.

Tiger muskies have long, cylindrical bodies with thin, compressed heads and elongated bottom jaws. They have vertical dark stripes. They tend to lurk near weeds in order to ambush their prey.

Many anglers seek out the fish because they can grow to 50 inches long and have a reputation for being a tough catch because of their size and strength. Compton said his department has received many inquiries about them since they were added to the North Crow.

“There’s a big following with the tiger muskie,” he said. “Certain anglers really love them.”

Game and Fish has been stocking the reservoir with brood stock rainbow trout, which are mature fish that have been used in hatcheries for their eggs. They’re typically large enough to avoid being eaten.

The eventual goal is to return the Upper North Crow to a trout fishery at some point as the sucker population decreases and the tiger muskies die off.

Crystal and Granite reservoirs, also located in Curt Gowdy State Park, are both stocked annually with rainbow and brown trout.

“There’s a high success rate of people catching them there,” Compton said.

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