SWAMP Banner

SWAMP - Mussel Watch Program

Mussel Watch Program/ Toxic Substances Monitoring (TSM)

Resources and Reports


  • State Mussel Watch Program (SMW)
    SMW was initiated in 1977 by the State Water Resources Control Board to provide a uniform statewide approach to the detection and evaluation of toxic substances in California coastal waters, bays, harbors, and estuaries. SMW measured trace metals and legacy organic contaminants in the tissue of transplanted mussels (Mytilus californianus) at more than 20 stations along the California coastline. Samples have been collected and analyzed annually from 1977 to 2010. SMW suffered from lack of funding since 2000 and as a result, California Department of Fish and Wildlife has been collecting and analyzing mussel samples from a limited number of sites since 2001. Eighteen sites are currently being monitored for the Water Boards by the California Department of Fish and Wildlife.
  • Regional Monitoring Program (RMP)
    Since 1993, six established SMW stations in San Francisco Bay have been monitored by the Regional Monitoring Program for Water Quality in the San Francisco Estuary (RMP). Contaminant data have been analyzed in bivalves at these six San Francisco Bay stations since 1977. In 1993, five additional stations were added, for a total of 11 stations in the RMP. In order to assess contaminant bioaccumulation throughout San Francisco Bay where salinity varies regionally, mussels, clams, or oysters were transplanted at nine saline or brackish stations, and Corbula amurensis were deployed at two freshwater stations (Sacramento River and San Joaquin River). Since 2006, organic contaminants have been analyzed biennially, and trace metals are analyzed every five years.
  • National Oceanic and Atmospheric Administration (NOAA) National Status and Trends (NS&T) Mussel Watch Program (NMW)
    In 1986, NOAA NS&T Program was created to characterize national spatial distributions and trends of contaminant concentrations in coastal environments and the Great Lakes. The NOAA NS&T Mussel Watch (NMW) Program measures concentrations of trace metals and legacy organic contaminants in resident mussels, Mytilus edulis and Mytilus californianus, from over 300 stations nationwide. Histopathology has also been conducted in mussels at NMW stations since 1995. NMW sampling was conducted annually until 1994 when sampling was reduced to biennial frequency. In 2007, the State Water Resources Control Board and Southern California Coastal Water Research Project (SCCWRP) collected mussels from 36-65 NMW stations in California and sent the samples to NOAA for analysis.


Bivalves (mussels, clams, and oysters) have been used as indicators of water quality in a number of monitoring efforts worldwide. Bivalves are filter feeders and can ingest and accumulate environmental contaminants. Monitoring bivalves for organic contaminants, trace metals and harmful algal toxins, can help managers identify sources, and help assess the bioavailability of contaminants at specific locations. In California, three primary long-term monitoring programs have used bivalves to monitor contaminants in coastal environments. Data from the State Mussel Watch, Regional Monitoring Program, and NOAA National Status and Trends Mussel Watch (described above) have provided evidence of significant decreases in concentrations of contaminants like lead, silver, pesticides, and polychlorinated biphenyls, since monitoring efforts began. The declines in these pollutants are likely the result of a combination of: chemical bans, increased regulations, increased source control, and improved wastewater treatment and stormwater management. In addition to looking at long-term pollution trends, Mussel Watch data can be used to identify specific locations in the California where contaminants have declined, and other sites where pollutants continue to be problematic. See more.

2010 Mussel Watch California Pilot Study: Contaminants of Emerging Concern

  • Summary

    In 2010, NOAA partnered with the State Water Board, San Francisco Estuary Institute, United States Geological Survey, and SCCWRP for the Contaminants of Emerging Concern Pilot Project (CEC Pilot Project) in order to gain a better understanding of the presence of CECs in California coastal waters. 167 CECs were measured in resident bivalves using established NOAA Mussel Watch stations. The most frequently detected CECs were: polybrominated diphenyl ethers (PBDEs-flame retardants), alkylphenols (fuel, detergent, and fragrance additives), and pharmaceutical and personal care products. CECs were present more frequently and in higher concentrations and in urban areas. CECs were particularly prevalent in mussels from sites near treated municipal wastewater effluent and stormwater discharges. Pharmaceutical and personal care products were present in all land uses (urban, low density, undeveloped, and agriculture). Agricultural areas had the highest concentrations of current use pesticides (e.g. chlorpyrifos), followed by urban areas. The CEC Pilot Project identified candidate CECs for future monitoring efforts as well as locations in California with problematic CEC contamination. The collaborative efforts of the local, state, and federal agencies for this project maximized available resources and enabled the project goals to be expanded and accomplished. Future inter-agency collaborations will help accomplish a common goal of gaining a better understanding of CECs in California coastal waters so that regulators can identify and address water quality issues. See more.


Trends at Mussel Watch Sites 1986-2009:

The numbers and names of sites in the boxes below coordinate with the sampling locations on the map above. Click on the name of an underlined sampling location to see associated graphs showing monitoring results from 1986-2009. Codes for sampling sites are listed in parentheses.

North Coast Sampling Locations

Central Coast Sampling Locations

  • 25. Carmel Bay (CBAP)
  • 26. Point Lobos (PLSR)
  • 27. Partington Point (PPJB)
  • 28. San Simeon Point (SSSS)
  • 29. Morro Bay (MBVG)
  • 31. Santa Maria River (SMPS)

Southern California Sampling Locations

Historical Data