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. There
are, however, no estimates of annual juvenile production for Central Valley spring-run Chinook
Salmon (“spring run”), a highly imperiled species in California, making it difficult to evaluate
population status and effectively manage key issues such as entrainment of this species at
water diversions. In recognition of this critical information gap, we initiated an effort to develop
a juvenile production estimate (JPE) for spring run, defined here as an annual forecast of the
number of juvenile Central Valley spring-run Chinook Salmon that enter the Sacramento–San
Joaquin Delta (“Delta”) from the Sacramento Valley. This metric would allow for a more robust
scientific assessment of the population, which is needed to effectively manage water to reduce
effects 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 the
key aspects of spring-run biology, examine the management and conservation importance of
a JPE, identify knowledge gaps, introduce new tools, and discuss alternative approaches to
forecasting the number of spring run emigrating from the Sacramento River drainage and into
the Delta. This paper summarizes the spring-run biology, monitoring, and emergent methods for
assessment considered at the workshop, as well as the guiding concepts identified by workshop
participants necessary to develop a JPE for spring-run Chinook Salmon.