The Oregon Department of Fish and Wildlife (DFW) is planning to stock up to 25,000 tiger trout in Douglass County’s Diamond Lake to exterminate tui chub, which until recently had not been seen in the lake since 2006. A routine sweep of the lake by a team of biologists last October found just one of the tiny minnows, but that was more than enough for the department to declare war.

“This is extremely frustrating when you consider the amount of time and effort put into the restoration of Diamond Lake by so many,” said Greg Huchko, DFW Umpqua District Fish Biologist, in a press release.

Huchko added that the fish was about six years old. Officials currently do not know how many tui chub are in the lake, but they are not taking any chances. The last time that the department grappled with the invasive species in Diamond Lake, it spent nearly $6 million to remove the species. It may seem like a drastic move by the agency, but considering that chub once completely infested the lake—with a population estimated over 90 million—in just a few years, it is not a fish to be taken lightly.

“I’m hoping it was the only tui chub, but I’m operating on the assumption that it wasn’t,” Huchko, who is now leading the effort, told the Mail Tribune. “I’m hoping, in a year or two, this becomes a non-issue.”

The fish is believed to have been originally introduced to the lake by fishermen using chub as live bait. In just a span of 10 years, the species grew exponentially and eventually became a threat to the lake’s most popular game fish, trout. The chub destabilized the food chain so much that it also caused a massive algae bloom that covered the lake. After several attempts to remove the chub, the DFW eventually decided to chemically treat the lake and eradicate the species entirely.

With the appearance of another tui chub, officials believe some anglers may be once again using the minnow as bait. The DFW is renewing its calls for fishermen to refrain from using tui chub—which as an invasive species, is illegal—and also to be aware of critters hitching a ride on their boats.

For now, Huchko says that the tiger trout should keep the chub population at a manageable level without having to resort to more damaging chemical treatments. Officials are continuing to monitor the lake’s waters to see if they can find more of the minnow.

Image courtesy Oregon Department of Fish and Wildlife

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