Last fall, the Oregon Department of Fish and Wildlife stocked East Lake just south of Bend with a Canadian strain of rainbow trout the agency hopes will help control a potentially explosive population of tui chub.

A fair number of these Blackwater trout are now being caught by anglers and ODFW is reminding anglers they can’t keep these fish as part of their daily bag limit.

“Right now, we’re evaluating the Blackwaters to see if they can help control tui chub populations,” said Jen Luke, ODFW fish biologist. “There may be some opportunity to harvest the Blackwater trout in the future but for now it’s strictly catch and release.”

Anglers can identify the Blackwater trout by the intact adipose fin, the small fin on the trout’s back between the tail and the large dorsal fin. Traditional hatchery rainbow trout have had the fin removed (fin-clipped) and may still be retained.

“If a rainbow trout still has its adipose fin anglers need to release it unharmed,” Luke said.

The release of 10,000 Blackwater trout into East Lake is a part of ODFW’s on-going efforts to control tui chub populations in lake. This strain of rainbow trout is very aggressive and within a year can begin feeding on small bait fish like tui chub.

According to Luke, tui chub are not native to the lake and were probably introduced in the 1920s when the use of live bait was legal.

“The chub has been in the lake for a long time and the populations are cyclical,” Luke said. “It’s gotten worse over the last 10 or 15 years and we were starting to get complaints from anglers about the quality of the trout and kokanee fisheries.”

Tui chub reproduce quickly and compete with rainbow trout and kokanee for food.

ODFW has used a two-prong approach to try to reduce and control tui chub numbers: trapping and removing tui chub when they gather on the shallow spawning grounds in the early summer, and introducing a top tier predator that will eat tui chub.

Since 2010, the agency and local volunteers have removed 48,500 pounds of tui chub from the lake (approximately 250,000 fish) with funding from the agency’s Fish Restoration and Enhancement Fund and matching funds from local angling clubs, OSU Cascades and local resorts. The goal is to knock down the tui chub population enough that it can be kept in check by Blackwater trout.

ODFW is using the same approach to remove chub from Paulina and Lava lakes. Paulina Lake has been stocked with the predatory Eagle Lakes strain of rainbow trout that, like the Blackwater, should prey on tui chub and grow to trophy size. Also like the Blackwater, the Eagle Lake trout are not fin-clipped and must be released unharmed.

Early indications suggest the chub removal in East Lake is paying off.

“We have data from 2011 and 2012 that show an overall improvement in health and condition of trout,” Luke said. “And anglers have been reporting this is one of the best years for trout fishing in East Lake in a long time.”

ODFW will continue to monitor the trout fishery and tui chub populations to see if trapping continues to be effective.

Image courtesy Oregon Department of Fish and Wildlife

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