Abundance and Relative Survival of Wild, ESA Listed Juvenile Winter Steelhead in a Tributary to the Lower Clackamas River, Oregon

It has been well documented that naturally spawning hatchery fish negatively impact population productivity and have lower adult survival than their wild counterparts (Araki et al. 2007; Chilcote 2003; Lynch and O'Hely 2001). Eagle Creek National Fish Hatchery spawns and rears juvenile coho salmon (Oncorhynchus kisutch) and juvenile steelhead trout (Oncorhynchus mykiss) that are released into Eagle Creek within the Clackamas River Basin, OR. The hatchery operates within the confines of the Endangered Species Act (ESA), however past investigations on the ecological and genetic impacts of hatchery steelhead in Eagle Creek indicated that in some years natural production was influenced by natural spawning of hatchery fish (Kavanagh et al. 2009).  Using Passive Integrated Transponder (PIT) tag technology, we initiated a three year study (2010-2012) comparing relative survival and abundance of juvenile steelhead in Eagle Creek to that in North Fork Eagle Creek, the primary producer of wild winter steelhead in the lower Clackamas River Basin.  Adult return data is being collected through 2015 and will be used to determine if freshwater productivity and survival in Eagle Creek is being impacted by naturally spawning hatchery fish.