Spawning Interactions Between Hatchery and Wild Steelhead and Spring Chinook Salmon in the Klickitat River, Washington: Results from Radio Telemetry and Genetic Investigations

Steelhead and spring Chinook salmon populations in the Klickitat River in south central Washington consist of both hatchery and wild fish.  Genetic monitoring indicates that hatchery and wild steelhead in the Klickitat remain distinct, suggesting low introgression rates.  Radio telemetry observations indicate spatial and temporal separation in spawning adult steelhead.  Of natural-origin steelhead that spawned in the wild, 64% spawned in the middle or upper mainstem Klickitat or in tributaries to this river reach, while 90% of hatchery steelhead spawned in the lower mainstem Klickitat or in tributaries to this reach.  Hatchery steelhead also exhibited a lower rate of spawning behavior in the wild.  For hatchery steelhead, observed spawning started in November, with 75% of the spawning ending by mid March.  For wild steelhead, 85% of spawning started after mid March and spawning ended in May.  In spring Chinook, genetic analysis indicates a high degree of interbreeding, and spatial and temporal overlap was observed in hatchery- and natural-origin spawners.  Different hatchery program characteristics and broodstock sources between these species are likely driving these contrasting results; reforms are planned with continued monitoring for both programs.  Monitoring of individual populations and programs is key to informed hatchery evaluations and management decisions.