A Long Term Monitoring Approach for Assessing Predation on Juvenile Salmonids by Native and Nonnative Fish in Two Impoundments of the Columbia River

Predation on migratory juvenile salmonids by native and nonnative fish is a significant factor affecting the survival of juvenile salmonids in the Lower Columbia River.  However, little work has been conducted within the Mid-Columbia River regarding fish predator effects.  The USGS in collaboration with the Washington Department of Fish and Wildlife (WDFW) has been working with Grant County PUD to increase our understanding of predator-prey interactions within the Mid-Columbia River.  Our approach has been to use previous studies from the Lower Columbia River as a model and then to employ technical advances in the biological sciences.  The current lack of long term data describing trends in salmonid predation in the Mid-Columbia River confounds our understanding of the effectiveness of actions being taken to mitigate predation.  During 2009 and 2010, the USGS and WDFW conducted field efforts to assess salmonid predation in Priest Rapids and Wanapum reservoirs of the Mid-Columbia River.  To assess predation during 2009 and 2010, we employed methodologies previously used in the Lower Columbia River to generate indices of abundance, consumption, and predation with the intent of using these data to provide a linkage to past studies and to help inform a new sampling design.  During 2011, we were slated to use the data collected during 2009 and 2010 to design and implement a status and trends monitoring framework for assessing predation effects in Priest Rapids and Wanapum reservoirs.  However, a shift in management priorities resulted in a change in project objectives that precluded the implementation of the design.  Consequently, we will present a conceptual framework for assessing the status and trends in predation using a probabilistic monitoring framework, existing data, and a Geographic Information System to incorporate habitat features into our sampling design. We will then provide an example of how to allocate samples over space and time based on our knowledge of the aquatic habitats, how predation risk is currently distributed in the study area, and the timing of juvenile salmonid outmigration.