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 STN and associated resources (e.g., abundance indices, sampling protocol, and copies of the STN databases) can be found on the CDFW Summer Townet Survey page..
Featured Publications
- Hartman and 3 co-authors published a paper in Estuaries and Coasts titled Hidden Complexities in the Base of the Pelagic Food Web: Correlates Between Zooplankton and Chlorophyll Vary by Functional Feeding Group. From the abstract, "these results indicate that management actions designed to increase phytoplankton abundance may be effective in freshwater areas where herbivorous taxa dominate but may be less effective in brackish-water areas where predatory and omnivorous taxa dominate. The increase in predatory copepods in brackish-water areas may increase food chain length and therefore decrease trophic efficiency in the transfer of carbon to fishes at the top of the food web."
- Tillotson, Lee, and Garcia recently published a paper in Endangered Species Research titled Association of delta smelt with other small pelagic fishes suggests the potential for competition and proxy monitoring. The authors applied a tree-based machine learning algorithm to evaluate habitat characteristics associated with detection of Delta smelt using paired data from a pelagic fish survey and a lower-trophic monitoring study. Preliminary analysis using models combining Delta smelt with a closely related species, or a broader set of potential surrogate pelagic fishes were better supported than models using only Delta smelt. Their results indicated that the closely related species and small pelagic fish community are utilizing similar habitats as Delta smelt and may serve as approximate proxies for Delta smelt in habitat modeling or other monitoring and analyses.
- Mahardja and 6 co-authors share a publication found in the San Francisco Estuary & Watershed Science titled Heatwaves and Rising Temperatures in the Upper San Francisco Estuary: Trends and Effects on Ecosystems and Humans. The goal of the paper is "...to identify key effects and uncertainties that surround heatwaves and rising temperatures in the upper estuary, which can subsequently be used to develop adaptation strategies and tools to manage such effects."
- The San Francisco Estuary Institute published a report "A Marsh Transformed: Historical Ecology and Landscape Change in Suisun Marsh" in December 2024 that compares the present state of the marsh with mid nineteenth century conditions. The 143-page report adds a new level of detail in the form of precise numbers and fine-scale mapping. You can read more about the future of Suisun Marsh as it faces possible submergence and development in the article " Suisun Marsh, a zone of potential in sinking ecosystem" featured on Maven's Notebook.
Featured Dataset Publications
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