Starting in the mid-1970's, beach seining has been conducted at numerous locations (Sampling Map) in the Lower Sacramento and San Joaquin Rivers, the Delta, and the San Francisco, Suisun, and San Pablo Bay areas. Each site is seined between two and four times monthly. A weekly beach seining survey is conducted to estimate the relative inter and intra-annual abundance and distribution of all races of salmonid fry using the delta as a rearing and nursery area. All native and non-native fishes are identified, measured, and enumerated. A midwater and Kodiak trawl survey is conducted in Sacramento (River mile 55) to estimate the relative abundance and timing of fry and smolts entering the delta.