2009-2012
Conventional wisdom once suggested that ecological conditions in the riverine environments that support salmon spawning determine variability in population abundance at return. More recently, however, it has been recognized and widely accepted that the ocean plays a critical role in determining salmon returns and fisheries catch (Mantua et al. 1997). In particular, the abundance of food (e.g., zooplankton) during the initial months of ocean life, when the salmon are small and most susceptible to predation, affects the at-sea survival of salmon as they first migrate to the sea and ultimately changes in populations years later when cohorts return to spawn. In this new project, supported by NASA-ROSES, we will integrate numerical and empirical-statistical modeling approaches (Wells et al. 2008) to enhance our knowledge of salmon survival at sea and improve abilities to forecast salmon population dynamics. The poor returns of Sacramento River fall run chinook salmon in 2007 and 2008, and resulting fisheries closures in 2008-present can be related to a period of anomalous ocean conditions in the California Current which began in 2004 and continued at least through 2006 (Wells et al. 2012).