Barb Gonzalez / File photo for The BulletinChinook and other salmon depend on copepods — small crustaceans — to eat. Cold currents help copepods grow large, but “the Blob” off the West Coast has raised the ocean temperatures, making for smaller copepods, which in turn hurts salmon.

State fisheries managers announced Friday that they will not open a spring Chinook season on the Lower Deschutes River this year because biologists predict the number of returning hatchery and wild stocks of the popular salmon will be too low.

Over the past several years, the number of spring Chinook returning from the Pacific Ocean to the Deschutes has been down, according to Rod French, district fish biologist with the Oregon Department of Fish and Wildlife in The Dalles.

“Smolt releases from Round Butte have remained constant in recent years, but the number of fish returning has been declining,” French said Friday in a news release. “We’re working to determine what’s causing the poor survival of these hatchery releases.”

It is unclear why the returns are down, according to the Department of Fish and Wildlife.

Fishing for spring Chinook was allowed in 2012 and 2014, but not in 2013, said Jessica Sall, spokeswoman for the department in Salem.

“It’s a season that we only open when we feel the run size can support a fishery,” she said.

Expecting another low return to Round Butte Hatchery this year, fisheries managers decided to close fishing of the spring run to ensure enough come back to the hatchery.

The fall runs, however, have been a different story in recent years, with the wild fall Chinook return one of the healthiest in the Columbia Basin. Department of Fish and Wildlife officials expect a return well above management goals and plan on opening a fishing season for fall Chinook on the Deschutes on Aug. 1.

“All indications are fishing could be as good as last year, when a near-record number of fall Chinook returned to the Deschutes and fishing was excellent,” French said.

— Reporter: 541-617-7812, ddarling@bendbulletin.com