Water in Mill Creek temporarily turned purple as part of effort to protect native fish

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MILLCREEK CANYON, Utah – Mill Creek might not look it’s usual color this week. That’s because wildlife experts are cleansing the waterway in Millcreek Canyon with a chemical agent to neutralize another chemical that’s clearing the creek of non-native fish.

When they’re finished, they’ll be populating it with Bonneville Cutthroat Trout.

Experts with the Division of Wildlife Resources say it’s not dangerous. It’s an agent called potassium permanganate. It is neutralizing the chemical rotenone, which is killing off non-native fish in the water.

Mike Slater with the DWR explains non-native fish would breed with Bonneville Cutthroat Trout and create hybrids if they did not manage them, causing them to overrun the river.

“There’s a lot of competition issues,” he said. “Brown trout, for example, will eat or will compete with the cutthroat that we eventually put in here. Rainbows that are here, they will actually breed with the cutthroat and we’d lose that genetic makeup.”

The potassium permanganate is causing the purple appearance of the water.

“We want to prevent this species–well, any species–for that matter, from being put on what we call the endangered species list,” Slater said. “Whenever that happens, it just adds a lot of complexity as to what you can and can’t do, whether it be you and I as the public, or even managing agencies.”

After the chemicals are flushed through and the non-native fish are removed, the DWR will repopulate the creek with Bonneville Cutthroat Trout.

The native trout being raised at the top of creek are about 6-inches long  and will be ready for anglers to catch in the next year.

“We’ve got scheduled about 6,000 of those fish that we’ll be putting back into the system,” Slater said.

Slater says Bonneville Cutthroat Trout create a more enjoyable experience for anglers fishing Millcreek Canyon.

“It’s a great way to protect the Bonneville Cutthroat Trout, let people understand the importance of that particular species, and we’re restoring another 9 miles of stream within the state of Utah that are home to the Bonneville Cutthroat Trout,” Slater said.

The chemical should run its course in the next few days, and officials with the DWR remind the public it’s not dangerous to animals or humans. They say it’s the same purifying agent used at water treatment plants.

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