About 1.2 million newly hatched Chinook salmon died at the Rapid River Fish Hatchery near Riggins, Idaho, after an oxygen-pump malfunction disrupted water flow, according to Idaho Fish and Game (IDFG).

The inch-long salmon represented roughly one-third of the hatchery’s annual production. They were scheduled for release in spring 2027 to begin their migration to the ocean and would not have returned as adults until 2030. The loss may have ripple effects on Chinook returns across the region—something many in Wyoming follow closely given the interconnected nature of Intermountain fisheries and conservation efforts.

IDFG says hatchery staff discovered the equipment failure on Nov. 18. The alarm system meant to alert workers to a malfunction also failed. Although staff quickly switched to a secondary pump, the short break in oxygenated water flow was enough to kill the young salmon.

To help reduce the long-term impact on fisheries, hatchery managers are coordinating with other facilities in the region. The cause of the equipment failure remains under investigation, and repairs are underway while remaining fish continue to be monitored.

Rapid River Fish Hatchery is located at the base of the Seven Devils Mountains near Riggins, Idaho.

Spring Chinook Salmon

Rapid River Fish Hatchery produces around three million spring Chinook smolts annually as part of Idaho Power’s mitigation program. Fish spend nearly two years at the hatchery where they grow to a length of 4-6 inches before the majority of these fish are released directly into Rapid River to begin their 45- to 60-day, 600-mile journey to the ocean. In addition, Idaho Power releases some of these fish into the Snake River below Hells Canyon Dam and some into the Little Salmon River. One to three years later, they return as adults to Idaho where they contribute significantly to sport and Native American tribal fisheries throughout the Columbia Basin.

Adult spring Chinook salmon arrive at the Rapid River trap from May to September. Fish are removed from the trap daily and transferred to holding ponds at the hatchery to await spawning. Spring Chinook salmon trapped in excess of broodstock needs are released back into fisheries or provided to humanitarian agencies for consumption. Additional spring Chinook salmon are trapped in the Snake River at Idaho Power’s Hells Canyon Trap and transported to Rapid River Fish Hatchery for use as broodstock.

Spawning begins around mid-August and is completed by the end of September. Each female produces 3,500 to 5,000 eggs which are placed into incubators after fertilization. Beginning in December and continuing through March, fry are moved from the incubators to outdoor raceways. In June, fish are moved into rearing ponds where they stay until their release as smolts the following March.

Since 1964, adult spring Chinook salmon returns to Rapid River Fish Hatchery have varied from less than 200 to more than 17,000. Migration and ocean conditions influence the subsequent return of adult salmon to Idaho. Rapid River Fish Hatchery has been rated one of the most successful hatcheries in the Pacific Northwest.