Ethan Brandt is optimistic that an experiment involving 43,000 rainbow trout will succeed.

Early indications are positive.

The laboratory, so to speak, is Thief Valley Reservoir.

The impoundment in the sagebrush country several miles east of North Powder, in Union County just north of the Baker County line, was created in the 1930s when the Powder River was dammed to store irrigation water for the Keating Valley.

Thief Valley has been a popular fishing spot for decades, and the Oregon Department of Fish and Wildlife stocks hatchery rainbow trout in the reservoir each spring.

But the 685-acre reservoir has emptied in several summers over the past decade — including 2024 — prompting ODFW to allow anglers to keep as many trout as they can catch to avoid wasting the fish the agency paid to raise in a hatchery and then truck to Thief Valley.

Historically, ODFW has waited until the next spring to replenish the reservoir’s trout population.

But Brandt, who is the district fish biologist at the agency’s La Grande office, conceived a different strategy in 2024.

Rather than delay stocking until the spring of 2025, which would give the trout little time to grow before the prime summer fishing season, he suggested ODFW release rainbow in the fall of 2024, after the reservoir started to refill, and then augment that release by stocking more trout in spring.

On Nov. 21, 2024, a pair of trucks loaded with trout disgorged about 43,000 fish into the reservoir, which was about 16% full. Most of the fish were between 5 and 8 inches long.

Although fish grow slowly in the cold water of winter, Brandt figured that by the spring of 2025, there would be a decent population of catchable rainbow (anglers can keep fish 8 inches or longer).

The concept seems to have proved out.

On June 18, Brandt’s colleague, Mike Lance, the assistant district fish biologist, visited Thief Valley and talked to several anglers who reported having good success catching rainbow from boats and from the shore.

Most fish were in the 12- to 15-inch range, Brandt said, which suggests that trout are starting to grow faster as the water warms.

Bank anglers said they were doing well using PowerBait.

Thief Valley was full as of June 19.

The reservoir drains relatively quickly, though, as water is released into the Powder River for irrigation.

With a drought worsening in Northeastern Oregon, Brandt said it’s quite possible Thief Valley will be emptied by late summer, leaving only the river in its old channel.