Science activity

Description The Diet and Condition study has provided information on the food habits of pelagic fishes in the estuary since 2005. We focus on the temporal and spatial differences in diet composition and feeding success of Delta Smelt, Striped Bass, Threadfin Shad, Longfin Smelt, Mississippi Silversides, and American Shad. Need Data from this project has been used to inform the Fall Low Salinity Habitat Program (FLaSH), Directed Outflow Project (DOP), and Management, Analysis and Synthesis Team reports, as well as life history models used for the conservation of fish and their habitats. Understanding what prey are utilized for food in the context of available prey, with the associated body-condition of fish, helps clarify the existence and timing of food limitation for young pelagic fish in the estuary. This work began as part of the Pelagic Organism Decline investigations and continued as a contributor to FLaSH investigations during which we in collaborated with the Fish Health Monitoring Project. Recently staff completed Longfin Smelt diet investigations as part element #296 (Longfin Smelt Investigations – in response to a litigation agreement) that will also contribute to the Longfin Smelt Conceptual Model and Synthesis effort (element #320). Finally, we will process Delta Smelt diets from investigations prompted by the Delta Smelt Resilience Strategy, and as part of the DOP. Objectives 1. What are the diets of pelagic fishes (especially Delta Smelt and Longfin Smelt) in the estuary and do they vary regionally or temporally? 2. Is there evidence of reduced feeding success spatially or temporally in the estuary? 3. Is feeding success associated with changes in relative weight or condition of fish? 4. Is there seasonal and regional overlap of diets between species (with a focus on age-0 Delta Smelt, Longfin Smelt, Striped Bass, Prickly Sculpin, Pacific Herring, and Threadfin Shad)?