The U.S. Geological Survey (USGS) California Water Science Center (CAWSC) is offering a funding opportunity to one or more member of the Cooperative Ecosystems Studies Unit (CESU) Program. The project is titled Studies on the Role of Zooplankton Density and Feeding Success in the Spawning Migration of Delta Smelt (Hypomesus transpacificus) in the Sacramento-San Joaquin Delta. This USGS-funded project will coordinate closely with a project titled Studies Assessing Factors that Influence Spawning Migration Behavior and Reproductive Condition of Delta Smelt (Hypomesus transpacificus) in the Sacramento-San Joaquin Delta. The USGS effort is comprised of several interrelated study components, three of which are included in this announcement: 1. Investigate the volume and composition of delta smelt diets retained during winter sampling; 2. Determine ambient zooplankton abundance, density and species composition to examine how food concentrations relate to delta smelt gut contents; and 3. Integrate findings of gut fullness and contents with data on delta smelt condition. The data will be used to refine behavioral components of particle tracking modules for use in individual-based models (IBMs) and other population models for delta smelt.