A tank hauled from Utah on the boat ramp at Phillips Reservoir on April 23, 2024, ready to disgorge its load of 70,000 tiger muskie larvae.

BAKER CITY — The battle against yellow perch in Phillips Reservoir continues.

The Oregon Department of Fish and Wildlife, which has been trying for well over a decade to pare the perch population in the reservoir, about 17 miles southwest of Baker City, is changing tactics.

On April 23 the agency released about 70,000 tiger muskie larvae in the 2,235-acre reservoir.

ODFW fish biologist Ethan Brandt hopes the tiger muskies will gobble perch at a rate that yields noticeable differences in the perch population and, eventually, in the number of rainbow trout available to anglers.

The reservoir was known for trophy trout fishing before someone, who has never been identified, illegally released yellow perch around 30 years ago.

The perch, which procreate prodigiously, eventually crowded out the rainbow trout and led to smaller average sizes for trout. ODFW still stocks thousands of hatchery rainbows in the reservoir each year.

ODFW estimated the perch population at 1.5 million.

The number of angler visits at the reservoir dropped by about 90%.

“If we can get even a half of a percent of survival from these (tiger muskies), we should see some significant changes to the perch population in the coming years,” Brandt said.

This isn’t the first time ODFW has released tiger muskies, a hybrid of the northern pike and the muskie, in Phillips.

Starting in 2013, and continuing for the next four years, the agency dumped 53,000 juvenile tiger muskies in the reservoir. Although the fish are sterile, ODFW biologists hoped their voracious appetite would thin the perch predominance.

But the experiment didn’t help much, Brandt said.

Many of the fish, which were about 5 inches long, were eaten by birds, Brandt said.

The tiger muskies released April 23, by contrast, are much smaller. About 10,000 of the 70,000 are around an inch and a half long, with the rest just three-quarters of an inch or so.

“We are hoping to overcome the survival bottleneck we have observed in the past and that these fish will be smarter at staying away from the surface of the water where birds can pick them off,” Brandt said.

He also hopes that because these fish were only in the hatchery for a short time, they will also be more wary of predators than tiger muskies that are raised longer in a hatchery.

Brandt plans to continue stocking the tiny muskies annually for at least five years.

The fish were raised in a hatchery operated by the Utah Division of Wildlife Resources.

Brandt said Utah has successfully stocked tiger muskie larvae in reservoirs in that state to control populations of other species.

Besides their potential to control perch, tiger muskies, which can grow to prodigious sizes, can also give anglers something else to catch.

Tiger muskies will continue to be a catch-and-release fish, however.

“This is probably one of the most exciting things that I have done since I have become the district fish biologist,” Brandt said. “I really hope we can meet our objectives of lowering the perch population, but I am also very excited that we may be able to provide a unique fishing opportunity that is only found in Phillips Lake, at least in Oregon.”

By law, Phillips is the only lake in Oregon where tiger muskies can be stocked now.

Brandt encourages anglers to heed the catch-and-release rule for tiger muskies. Poaching of the fish in the past decade made the experiment less successful, he said.

“Harvesting these fish will not allow them to grow large and to have as great of an effect on the perch population,” he said. “Releasing them back into the water will allow others to catch this rare trophy fish.”

The sterile fish can live for 15 years or so and grow to 2 feet or more.

Biologists have said in the past that tiger muskies are difficult to catch compared with trout — or perch.

Prior to releasing tiger muskies, ODFW biologists tried to control perch by using a net trap to catch several hundred thousand of the fish starting in 2008.

But the fish reproduce so quickly that any benefits from the trapping were ephemeral.

Biologists acknowledged, when tiger muskies were initially released, that the fish would eat some trout as well as the more numerous perch.

But they hoped the net benefit would be on the side of the trout.

“If we can get even a half of a percent of survival from these (tiger muskies), we should see some significant changes to the perch population in the coming years.”

— Ethan Brandt, fish biologist, Oregon Department of Fish and Wildlife