Considerations for the Development of a Juvenile Production Estimate for Central Valley Spring-Run Chinook Salmon

Effective species management depends on accurate estimates of population size. Thereare, however, no estimates of annual juvenile production for Central Valley spring-run ChinookSalmon (“spring run”), a highly imperiled species in California, making it difficult to evaluatepopulation status and effectively manage key issues such as entrainment of this species atwater diversions. In recognition of this critical information gap, we initiated an effort to developa juvenile production estimate (JPE) for spring run, defined here as an annual forecast of thenumber of juvenile Central Valley spring-run Chinook Salmon that enter the Sacramento–SanJoaquin Delta (“Delta”) from the Sacramento Valley. This metric would allow for a more robustscientific assessment of the population, which is needed to effectively manage water to reduceeffects on spring run, a key condition of state permit requirements. To help guide this effort,we organized a workshop for stake-holders, managers, and scientists to review some of thekey aspects of spring-run biology, examine the management and conservation importance ofa JPE, identify knowledge gaps, introduce new tools, and discuss alternative approaches toforecasting the number of spring run emigrating from the Sacramento River drainage and intothe Delta. This paper summarizes the spring-run biology, monitoring, and emergent methods forassessment considered at the workshop, as well as the guiding concepts identified by workshopparticipants necessary to develop a JPE for spring-run Chinook Salmon.