The Nez Perce Tribe and Columbia River Inter-Tribal Fish Commission released 37 wild steelhead into the Snake River below Lower Granite Dam in hopes of boosting the number of spawning steelhead.
The Lewiston Tribune reports the fish, known as kelts, were previously captured at the dam as they tried to return to the ocean after spawning in their natal streams.
They were held for one or two years at Dworshak National Fish Hatchery to allow them to regain strength, and they were released Tuesday, ready to spawn once again.
Steelhead are unique among anadromous fish — fish that migrate from the sea to reproduce — in that they don't necessarily die after spawning. Still, it's rare for female steelhead to make it as far as the Lower Granite Dam to spawn a second time.
Less than half a percent of Snake River steelhead are able to make the repeat trip on their own, said Doug Hatch, a fisheries scientist with the Columbia River Inter-Tribal Fish Commission at Portland, Oregon. The repeat spawners have on average about 5,000 eggs.
"They are really valuable fish," Hatch said. "They have about a third more eggs than the fish that are coming back (for the first time.) These repeat spawners are larger and have more eggs than first-time spawners, so they are super valuable."
Wild Snake River steelhead are listed as threatened under the Endangered Species Act, and this fall's steelhead run is shaping up to be one of the worst on record. The kelt program is listed as one of the emergency responses that could be implemented when fish numbers are alarmingly low.
The National Marine Fisheries Service said this week that steelhead numbers have declined steeply since a robust return recorded in 2014. The decline is prompting a review by federal officials to determine if additional steps should be taken to help the species.