Interagency Ecological Program San Francisco Estuary Smelt Larva Survey 2009 – 2022

The Interagency Ecological Program San Francisco Estuary Smelt Larva Survey was initiated by the California Department of Fish and Wildlife (CDFW) in 2009 to monitor the distribution and abundance of newly-hatched Longfin Smelt (Spirinchus thaleichthys) in the San Francisco Estuary. Surveys are conducted bi-weekly and sampling begins in December, and continues through March. The surveys sample at fixed locations, stations, from Carquinez Strait through Suisun Bay and into the Sacramento-San Joaquin River Delta. Napa River stations were added in 2014.Each survey consists of 44 stations. At each station, one 10 minute stepped-oblique (bottom to top) tow is made following a prescribed tow schedule. The net is a conical 505 µm mesh lashed to a D shaped frame mounted on skis. Larval fish samples are preserved in the field in 10% Formalin and brought back to the CDFW Stockton Lab for identification to species and enumeration under a microscope. Several types of data are collected at each station in addition to the larval fish sample, including the volume of water sampled by the net, surface water temperature, surface and bottom specific conductance (EC normalized at 25˚C), Secchi disk depth, tow duration, tidal condition, and surface water turbidity.