Improving Hatchery Rearing Methods for Steelhead in the Pacific Northwest

We research ways to improve the performance of hatchery-produced steelhead trout to promote recovery and sustainable fisheries.

West Coast

Steelhead trout (Oncorhynchus mykiss) are cultured throughout the Pacific Northwest to:

Recover threatened or endangered populations.
Provide harvest opportunities for tribal and recreational fisheries.

However, steelhead have an extended and highly variable freshwater life cycle component making them difficult to raise in captivity without adverse effects.

Four classes of steelhead typical of hatchery rearing (parr, transitional, smolt, and mature male). The proportions in each class at release vary with rearing methodology and broodstock source. It is desirable to produce a high proportion of smolts and transitional steelhead, as parr and mature males residualize with consequences for limiting ecological interactions and genetic management of integrated populations. (Photo credit, Michael Humling, USFWS) — Four classes of steelhead typical of hatchery rearing (parr, transitional, smolt, and mature male). The proportions in each class at release vary with rearing methodology and broodstock source. It is desirable to produce a high proportion of smolts and transitional steelhead, as parr and mature males residualize with consequences for limiting ecological interactions and genetic management of integrated populations.

Almost all hatchery steelhead are raised to become yearling smolts. Meanwhile, smolts from natural populations migrate to sea anywhere from age-1 to age-4. Altering the life cycle by quickly growing fish may cause domestication and rapid reproductive fitness loss when hatchery-produced fish spawn naturally. Releasing steelhead at the wrong age, size, or physiological state reduces hatcheries' effectiveness and promotes negative ecological interactions with natural populations of steelhead and other species.

Research

We conduct research to:

Develop and test hatchery culture methods for steelhead that optimize production of smolts at release through hatchery- and laboratory-scale research.
Identify behavioral, genetic, and physiological mechanisms of domestication selection in hatchery environments.
Assess and improve the fitness of hatchery steelhead produced using different rearing methods.
Reduce the production of mature males to simplify the genetic management of natural populations.
Reduce the production of immature parr in hatchery environments to reduce ecological interactions upon release.

Projects

Evaluate the performance of age-2 steelhead smolts produced from natural-origin broodstock at the Winthrop National Fish Hatchery.
Develop models to compare survival outcomes during a complete migratory life-cycle for alternative rearing strategies.
Test the feasibility of split-age rearing strategies (age-1 and age-2 smolts produced from a single broodyear) based on early growth rates.
Develop a tool for steelhead hatcheries to determine optimal rearing strategy (age-1, age-2, or split-age) based on spawn timing of broodstock and hatchery rearing water temperature.

Collaborators

United States Fish and Wildlife Service
Washington Department of Fish and Wildlife
University of Washington
Environmental and Fisheries Sciences Division, Ecological Physiology Program at the Northwest Fisheries Science Center
Conservation Biology Division, Genetics and Evolution Program at the Northwest Fisheries Science Center