Concentrations of contaminants such as methylmercury and pesticides in sport fish were found to be low at the majority of locations sampled in the first-ever systematic statewide survey of California rivers and streams.
The fish survey, conducted by the State Water Resources Control Board’s Surface Water Ambient Monitoring Program (SWAMP), surveyed sport fish from 63 locations in 2011.
The survey analyzed sport fish because they provide information on potential human exposure to contaminants, and on the condition of the aquatic food web.
Other pollutants, including dieldrin, PCBs, DDT, chlordanes and selenium were also analyzed, but were not found at high enough concentrations to be a problem.
While a majority of areas sampled had low concentrations of methylmercury and pesticides, fish high in the food chain in the Sacramento-San Joaquin Delta region – such as largemouth, smallmouth and striped bass, and Sacramento pikeminnow – showed a high accumulation of methylmercury, the report showed.
Water from Clear Lake reaches the delta through Cache Creek and the Yolo Bypass. Locations within Lake County specifically were not tested in this initial study.
Nearby locations that were tested included the Van Arsdale fishing counting station on the Eel River, Cold Creek at Pottery Valley and the Coyote Valley Dam egg collection area on the Russian River, according to the report.
Methylmercury can affect the developing nervous system of children and adolescents, potentially leading to learning disabilities.
Methylmercury contamination of California rivers and streams likely originates from multiple sources, including historic mercury, gold and silver mining; global emissions to the atmosphere; and urban and industrial wastewater and storm water.
Methylmercury is generally a low concern in high elevation locations where trout species predominate and where most of the fishing spots sampled were located.
The initial screening study is a first step in an effort to identify and quantify contaminants in California’s rivers and streams to provide a detailed evaluation of human and wildlife exposure, and to establish priorities for cleanup actions.
In this survey, 568 fish representing 16 species were collected from 63 popular river and stream fishing locations throughout California. Where possible, multiple species were analyzed at each location.
Trout species and salmon had low concentrations of methylmercury and other contaminants. Cleaner species were frequently present alongside the species with high concentrations at the contaminated locations.
The River and Stream Survey was funded by the State Water Resources Control Board’s Surface Water Ambient Monitoring Program and the United States Environmental Protection Agency.
The survey is one component of a new program to track sport fish contamination in all California water bodies. Results from a survey of the state’s lakes were reported three years ago, and results for the coast were published last year.
The public can access results for individual fishing locations including the Coast Survey and the Lakes Survey through the California Water Quality Monitoring Council’s “My Water Quality” Web portal at www.CaWaterQuality.net . Information on sport fish contamination can be accessed by clicking on “Is It Safe to Eat Fish and Shellfish from Our Waters?”
The River and Stream Survey Report is available on the SWAMP Web site at http://www.waterboards.ca.gov/water_issues/programs/swamp/rivers_study.shtml .