Development of a study design and implementation plan to estimate juvenile salmon survival in Lookout Point Reservoir and other reservoirs of the Willamette Project, western Oregon

Abstract

Survival estimates for juvenile salmon and steelhead fry in reservoirs impounded by high head dams are coveted data by resource managers. However, this information is difficult to obtain because these fish are too small for tagging using conventional methods such as passive-integrated transponders or radio or acoustic transmitters. We developed a study design and implementation plan to conduct a pilot evaluation that would assess the performance of two models for estimating fry survival in a field setting. The first model is a staggered-release recovery model that was described by Skalski and others (2009) and Skalski (2016). The second model is a parentage-based tagging N -mixture model that was developed and described in this document. Both models are conceptually and statistically sound, but neither has been evaluated in the field. In this document we provide an overview of a proposed study for 2017 in Lookout Point Reservoir, Oregon, that will evaluate survival of Chinook salmon fry using both models. This approach will allow us to test each model and compare survival estimates, to determine model performance and better understand these study designs using field-collected data.