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Associated Press

LIVINGSTON (AP) — The creeks meandering through Charlie Pierson’s ranch are teeming with fish.

But these aren’t just any fish, scientists have excitedly discovered over the last 10 years. They are genetically pure cutthroat trout.

Somehow, rainbow trout, a nonnative fish which tends to dominate and interbreed with the Yellowstone River’s native cutthroats, haven’t found their way into Locke Creek, which crosses Pierson’s property. The tiny tributary is a spawning haven for a fish species striving to keep a stronghold in its indigenous waters.

The discovery has led to a unique partnership between Pierson and the state Department of Fish, Wildlife and Parks. FWP fisheries biologist Brad Shepard said hopefully the project will encourage even more cutthroats to spawn in Locke Creek.

Pierson will get a better irrigation source. Cutthroats will get what might be a first-class spawning ground.

Pierson’s ranch, the Highland Livestock Co., has long used Locke Creek to water about 600 acres by pump and flood irrigation. However, a study by a Montana State University graduate student found the lower the water levels on Locke Creek, the lower the numbers of cutthroat fingerlings making it to the Yellowstone.

Shepard said the FWP therefore became interested in keeping water levels as high as possible in Locke Creek. Also, three cement head gates block fish access to the creek. The FWP wanted to remove them in hopes of giving cutthroat more room to spawn.

“Up until now, the fish have only been able to spawn in the lower part of the creek,” Shepard said.

Pierson came up with an idea. “I thought maybe we can replace the water in Locke Creek with a well,” he said.

FWP agreed. So the agency, through its Future Fisheries Program, will soon complete a 30-year lease on Pierson’s water rights to Locke Creek.

In exchange, FWP will pay Pierson $45,000. The money goes toward drilling a well into the aquifer, buying a pump to get the water out and buying a windmill to power the ranch.

“I think this is good deal for everyone,” Shepard said. “Charlie gets what he needs, we get what we want and hopefully the fish get what they want.”

Pierson said he gets a more reliable water source. The well, installed in April, pumps 300 gallons a minute and is just 40 feet deep. “It’s better because the creek may be dry before the summer is out,” he said.

Installing the electricity-generating windmill was especially attractive to FWP, Shepard said. Electricity prices might rise drastically, but Pierson’s ranch will be self-sufficient. Therefore, Highland Livestock Co. will still be able to afford the power to pump water and not revert to flood irrigation.

As for the fish, they will have more room to spawn.

The MSU study found that in a good water year about 3,000 to 5,000 cutthroat fingerlings hatch in Locke Creek, which translates into 400 to 500 adult fish. Shepard said he hopes the changes will mean 5,000 to 10,000 fingerlings, or 500 to 1,000 adult fish.

And cutthroats’ tendency to return to their birthplace to spawn is extremely high, Shepard said. Those additional fish will likely use the tributary in the future.

The reason rainbows haven’t invaded Locke Creek remains a mystery. But both men have their theories.

Pierson believes he trapped cutthroats in part of Locke Creek when he built his uppermost head gate 20 years ago. The head gate presents a three-foot concrete barrier to fish.

Therefore, rainbows can’t get up the creek. But high waters wash small cutthroats out and down to the Yellowstone.

FWP plans to keep in the upper head gate for now in case Pierson’s theory proves true and rainbows begin using Locke Creek.

Shepard’s theory relies on the water levels of the Yellowstone. He said cutthroats generally spawn earlier in the year than rainbows.

There is a culvert on Locke Creek beneath the railroad tracks, not far from the main river. Shepard thinks the Yellowstone is higher at the same time cutthroats want to spawn — high enough to get beyond the railroad culvert. But the culvert might be impassable by the time the rainbows want to spawn, which is often two to four weeks after the cutthroats.

Biologists will monitor the creek next year to determine if rainbows invade. All sides hope the project proves beneficial to cutthroats.

“We’re really concerned about the possibility of rainbows moving in,” Shepard said. “These are genetically pure fish.”

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