Ecological and Genetic Impacts of Hatchery Steelhead Releases on Wild, ESA Listed Fish Populations in a Tributary to the Lower Clackamas River, Oregon

Eagle Creek National Fish Hatchery spawns and raises juvenile coho salmon (Oncorhynchus kisutch) and juvenile steelhead trout (Oncorhynchus mykiss) that are released into Eagle Creek within the Clackamas River Basin.  The hatchery operates within the confines of the Endangered Species Act (ESA), however limited information exists on the ecology and biology of wild ESA listed fish in Eagle Creek.  From 2005-2009, we evaluated the ecological and genetic interactions between a hatchery stock of steelhead raised at Eagle Creek National Fish Hatchery for harvest and a U.S. Endangered Species Act threatened steelhead population in Eagle Creek, Oregon.  We monitored adult returns, hatchery smolt releases, abundance and habitat selection of juvenile fish, and genetic structure of hatchery and wild origin steelhead. From our findings, we concluded that hatchery steelhead may pose an ecological risk to wild steelhead in Eagle Creek, particularly at the juvenile/smolt stage.  We found that hatchery residuals made up approximately nine percent of the yearling stream population and one percent of the subyearling stream population of steelhead.  Although no displacement of wild fish was documented, the abundance of hatchery residuals may still pose a risk to the wild steelhead in Eagle Creek.  Additionally, genetic analyses indicated that in some years natural production in upper Eagle Creek was influenced by natural spawning of hatchery steelhead.  Based on these findings, we hypothesize that freshwater productivity, survival, and spawner recruitment rates in upper Eagle Creek are impacted by naturally spawning hatchery fish. 

In 2010, we initiated a three year study comparing survival and abundance of juvenile steelhead in Eagle and North Fork Eagle Creeks using Passive Integrated Transponder (PIT) tag technology.  The data collected will help us estimate relative survival of winter steelhead in Eagle and North Fork Eagle Creeks, estimate life stage specific survival (young of year to yearling and smolt to adult), and determine migration timing of winter steelhead.  When evaluating the program at Eagle Creek we try to consider the full biological, social and economic value the steelhead fishery brings to the Clackamas River Basin.  The recommendations from this study are designed to improve hatchery and genetic management practices, assist with conservation and recovery of ESA listed populations, and contribute to recreational, commercial and tribal harvest.