State Fish Advisory for Oso Flaco Lake: Choose Bluegill and Hitch But Avoid Goldfish


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SACRAMENTO – A new state sport fish advisory for San Luis Obispo County’s Oso Flaco Lake recommends eating the lake’s bluegill and hitch, limiting consumption of its largemouth bass and avoiding its goldfish.

The recommendations are based on the levels of certain pesticides, PCBs, and methylmercury in different fish species in the lake. The advisory and eating guidelines were developed by the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA).

Oso Flaco Lake is part of the Oceano Dunes State Vehicular Recreation Area, a California State Park. To develop the advisory, OEHHA used data from sampling funded by California State Parks, the State Water Resources Control Board, and the Central Coast Regional Water Quality Control Board.

“Eating fish provides important health benefits, including reducing the risk of heart disease. These guidelines balance those benefits against the health risks from exposure to contaminants in fish,” said OEHHA Director Dr. George Alexeeff.

More than 50 fish from the lake were collected and analyzed for the presence of contaminants. The pesticides the fish were tested for—chlordanes, DDTs, and dieldrin—are legacy chemicals that have been prohibited for many years due to their high toxicity and persistence in the environment. Although all three types of contaminants were detected, they were not always found at levels high enough to cause health concerns.

Methylmercury can harm the brain and nervous system of people, especially in fetuses and children as they grow. The pesticides in question may cause cancer and other health effects. PCBs affect many body functions, including effects on the nervous system, and can cause cancer and other health effects.

The new guidelines recommend that all individuals avoid eating any goldfish from the lake. Goldfish tested from the lake had high levels of DDTs, dieldrin, and PCBs.

The lake’s bluegill and hitch have lower levels of contaminants. Anglers can safely eat as many as seven servings per week of these species.

OEHHA recommends that largemouth bass from the lake can be safely eaten once per week by children and women up to 45 years old. Women who are older than 45 and men can eat up to two servings per week of the lake’s largemouth bass.

The Oso Flaco Lake advisory is based on data from the State Water Resources Control Board’s Toxic Substances Monitoring Study and the Surface Water Ambient Monitoring Program. California State Parks provided funding to have additional species collected and analyzed.

Health Advisory and Guidelines for Eating Fish from Oso Flaco Lake and other bodies of water. The site also includes advisories and eating guidelines for more than 50 other California water bodies, as well as statewide advice for lakes and reservoirs that do not have site-specific advisories.

OEHHA is the primary state entity for the assessment of risks posed by chemical contaminants in the environment. Its mission is to protect and enhance public health and the environment by scientific evaluation of risks posed by hazardous substances.