Sport anglers are asking state fish biologists to add a month to the window time when they can keep wild Rogue River spring chinook salmon as part of a study to gauge whether angler pressure is a major factor in why the wild run here is depressed.

Two Curry County sport-angling groups have petitioned the Oregon Fish and Wildlife Commission for a five-year experimental fishery that would allow anglers to keep wild spring chinook beginning May 1 instead of June 1 on the lower and middle Rogue.

The Oregon Department of Fish and Wildlife's current Rogue River Spring Chinook Management plan sets the June 1 start to the wild-fish season to protect the early portion of the run from angler harvest. Until then, anglers rely on catching hatchery fish to keep, but catch rates on hatchery fish are much lower than on wild fish during that time, particularly in the lower Rogue bay.

Curry Sport Fishing Association and Oregon South Coast Fishermen, which are joined by retired ODFW biologist Tom Satterthwaite — one of the chief architects of that plan — argue that harvest rates on wild spring chinook are already well beneath plan limits.

They believe improved upper Rogue spawning habitat would do better at growing wild spring chinook numbers than just forcing anglers in May to keep only hatchery spring chinook, whose numbers have dwindled steadily.

"By doing this experimental fishery, we should be much better able to delineate whether it's a harvest issue or a habitat issue," says Steve Beyerlin, a retired lower Rogue guide involved in the petition. "It should be able to show if harvest is really a limiting factor, and I don't think it is."

If supported, such a conclusion could lead to possible shifts stressing habitat improvements in the upper Rogue instead of over-emphasizing angling impacts when the plan is reviewed again in 2022.

The commission will take up the petition when it meets Dec. 8 in Salem.

An ODFW staff summary report recommends the commission deny the petition, saying the current and ongoing review of the spring chinook plan will address enlarging the window of when anglers can keep wild fish if the review supports it.

The report states that information supplied in the petition will be considered during this review.

Wild spring chinook have been the fish most impacted by the placement and operation of Lost Creek dam, which eliminated about one-third of its historic spawning grounds.

The management plan was adopted in 2007 after lengthy input from a committee whose majority preferred the approach to boost habitat and lean less on anglers. Ultimately, the current plan was adopted by the commission.

When the plan was adopted, ODFW estimated that the Rogue's wild spring chinook population that spawned naturally averaged 7,600 fish over the previous 10 years.

In 2016, the 10-year running estimate was 8,960, the ODFW staff report states. The plan's desired status is a sustained 15,000 wild spring chinook reaching the upper Rogue where they spawn, the report states.

"We're following the plan," ODFW biologist Pete Samarin says. "According to the plan, there is nothing warranting early harvest at this time.

"I think this is a reaction to the lack of hatchery fish," he says.

— Reach Mail Tribune reporter Mark Freeman at 541-776-4470 or mfreeman@mailtribune.com. Follow him on Twitter at www.twitter.com/MTwriterFreeman.