The Interagency Ecological Program’s (IEP) Summer Townet Survey (STN) is a long-term effort to monitor young pelagic fishes in the upper San Francisco Estuary (California, United States). Conducted by the California Department of Fish and Wildlife (CDFW) since 1959, STN has sampled fixed locations from Eastern San Pablo Bay to Rio Vista on the Sacramento River, and to Stockton on the San Joaquin River; and a single station in the lower Napa River. The study area was expanded in 2011 to include the Sacramento Deep Water Ship Channel and Cache Slough. Currently, 40 stations are sampled as a “survey” every other week June through August for 6 surveys. A conical, fixed-frame net, is pulled obliquely through the water column 2 to 3 times at each station. Fish catch, length-frequency, and catch-per-unit-effort (CPUE) among stations is available with data visualization tools on the study website for all species (Summer Townet Survey (ca.gov)). Data collected at 31 stations are used to calculate annual relative abundance indices for age-0 Striped Bass (Morone saxatilis) and Delta Smelt (Hypomesus transpacificus). The remaining 8 stations are sampled to expand our sampling range further upriver and increase our understanding of larval and juvenile fish abundance and distribution in the lower Napa River and the North Delta. In 2005, STN added a meso-zooplankton net to assess fish food resources at each station and a subset of the fish collected are retained for diet analysis by CDFW researchers (see STN and FMWT zooplankton data on EDI). The STN also measures habitat conditions via water temperature (°C), water clarity (Secchi disk depth), Turbidity (NTU) and specific conductivity (µs/cm). Managers and researchers use the data collected by STN to inform decisions and improve our understanding of the health of the upper San Francisco Estuary.