TRAIL — The metal trap closes slowly, forcing dozens of ripened Rogue River winter steelhead from the Cole Rivers Hatchery collection pond and into the sorting room for processing, all nice specimens but certainly not Wednesday's target species.

Technicians earlier thought the first spring chinook of the year had reached Cole Rivers, but the highly coveted salmon were conspicuously missing during Wednesday's collection-pond sweep.

"Doesn't look like it's here yet," hatchery foreman Jim Grieve says.

By next week's sweep, the first springer of the year likely will be there. And it will be followed by 6,483 others before the run to the hatchery is over, give or take 1,800.

They'll be joined in the upper Rogue by 9,729 wild spring chinook, give or take 2,354.

Those are the results of the first-ever preseason forecast for what anglers can expect during the much-anticipated spring chinook season, which is about to envelop the river community like no other run of fish does.

The reason for the inaugural estimate is because, finally, biologists can.

Five years of scale samples from spawning springers, as well as other factors, have created just enough data to create computer models for predicting wild fish returns over what used to be Gold Ray Dam and hatchery chinook returns to Cole Rivers.

They're not generated with enough confidence for their creator, Oregon Department of Fish and Wildlife fish biologist Pete Samarin, to bet a paycheck on their accuracy. At least not yet. Accuracy will be honed as more data gets punched into the model in future years.

"That's the best we can do with the data that's available," Samarin says. "There's a lot of refining to do to add confidence to that.

"There's more to be done before this is a well oiled machine," he says.

This machine actually exists because of two things — the Rogue's Spring Chinook Salmon Management Plan and a now-extinct chunk of concrete called Gold Ray Dam.

For six decades, spring chinook were counted as they swam through the dam's counting station, providing a tally of chinook in the upper Rogue. The wild fish counted provided a running tally used to determine whether there were enough to trigger opening wild spring chinook harvest river-wide, a move anglers want to see, because some years they catch and release about five wild chinook for every one hatchery keeper they catch.

While the dam counts provided numbers, it didn't supply accurate fish ages, which are critical to preseason predictions, because counts of the age composition from last year's run are a key ingredient in this highly variable exercise.

With the dam gone, the only way to judge wild spring chinook numbers is to survey spawning grounds to count spawners and collect scale samples to put under microscopes, where the chinook's ages are revealed.

Samarin now has numbers and age estimates for wild spring chinook returns for five years, which is just enough to crunch a model worth at least betting lunch over.

That allows biologists such as Samarin to recreate the run mathematically. Adding crucial data such as ocean temperatures and wind directions when that year's offspring hit the ocean the following summer helps estimate survival rates when they return to the river at age 3 or 4, the two most dominant year classes in each year's Rogue return.

More years of data means more accuracy and therefore greater chance for anglers to put a wild Rogue springer — which everyone outside of the Columbia River says are the best-eating fish caught in Oregon fresh water — in the fish box in May.

But not this year.

Rogue anglers will again wait until July 1 to consider killing wild Rogue spring chinook they catch below Dodge Bridge.

Instead they'll again be targeting fin-clipped hatchery springers, and years of catch data show that anglers catch one of every four of the hatchery springers that reach the upper Rogue.

And the preseason forecast for that is 1,621 springers headed to barbecues, give or take 612.  

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