Featured Survey
The Summer Townet Survey (STN) is one of the longest running long-term fish monitoring programs. 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 survey was initially started to monitor age-0 Striped Bass (Morone saxatilis) and later began to monitor Delta Smelt (Hypomesus transpacificus), a sensitive native species believed responsive to the proper functioning of the Delta region. Data collected at 31 index stations are used to calculate annual relative abundance indices for age-0 Striped Bass and Delta Smelt. The study area was expanded in 2011 to include stations located within the Sacramento Deep Water Ship Chanel and Cache Slough for a total of 40 stations. These stations are sampled every other week June through August.
In addition to fish, the STN also measures environmental variables including water temperature (°C), water clarity (Secchi Depth & NTU) and specific conductivity (µS/cm). Managers and researchers use the data collected by STN to monitor long-term trends in the fish and invertebrate community, monitor the diet and condition of important predator and prey fish species, detect the introduction of new and potentially invasive species, inform decisions and improve the understanding of the health of the San Francisco Estuary.
Additional information on abundance indices, sampling protocol, and copies of the STN databases can be found on the CDFW FTP site for the Townet and Fall Midwater Trawl.
Featured Publications
Featured Datasets
- Updated CDFW 20-mm Survey and Smelt Larva Survey Data
New data for the IEP San Francisco Estuary 20-mm Survey (20-mm) has been uploaded to EDI and is now available. Data for 2026 data is still being processed and is expected to be released by the end of the year. Initiated in 1995, the CDFW 20-mm Survey monitors the distribution and abundance of post-larval and juvenile Delta Smelt (Hypomesus transpacificus). Young of the Year Delta Smelt are considered juveniles at sizes greater than or equal to 20-mm, and this survey focuses on that life stage.
New data for the IEP San Francisco Estuary Smelt Larva Survey (SLS) was uploaded to EDI in May. Initiated in 2009, the SLS survey monitors the distribution and abundance of newly hatched Longfin Smelt (Spirinchus thaleichthys) in the San Francisco Estuary.
- Got something new to share? Contact us at iep@wildlife.ca.gov.
- Looking for IEP Datasets? Visit the IEP Survey Data page.
Featured Websites
- Seasonal Monitoring Report
The seasonal monitoring report was created to provide managers with an overview of the trends associated with different environmental ad biological parameters in the system. The IEP Seasonal Monitoring Report presents the full time series for selected water quality, plankton, and fisheries surveys conducted by IEP in a single graphical report. Time series are presented separately for 3 major regions: Delta, Suisun, and San Pablo Bay. The report is developed by the IEP Synthesis Team, and reviewed by the Science Management Team and Coordinators before publication.
- Frontiers for Young Minds
Where the river meets the ocean - Stories from San Francisco Estuary