Mercury is toxic, but what about pesticides? It seems that some fish farms in Norway treat salmon with unauthorized pesticides. On 3 June 2013, the French " Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail (Anses) has downed the recommendations from 3 times a week to not more than twice a week, because it is not sure whether the benefits of eating (a.o. fatty) fish like e.g. salmon but also sweet water fish ("bio-accumulators") are higher than the negative risk due over-exposition to chemicals. In other words, testing fish for mercury is one thing, but does it allow concluding on the extent to which fish is "safe", knowing that some fish may contain other toxic substances?
FDA and EPA: Pregnant and Breast-Feeding Women Should Eat More Fish — Physician’s First Watch
FDA and EPA: Pregnant and Breast-Feeding Women Should Eat More Fish
By Kristin J. Kelley
Pregnant women and those who might become pregnant, as well as breast-feeding women and children, should eat of a variety of fish two to three times a week (8–12 oz. weekly) to support growth and development, the FDA and EPA recommend in draft guidance. The fish should be low in mercury (e.g., canned light tuna, catfish, cod, salmon, tilapia).
The recommendation, which is consistent with the USDA's 2010 Dietary Guidelines for Americans, also advises against eating the following types of fish because they contain higher levels of methylmercury:
Albacore tuna (limit of 6 oz./week)
Tilefish (from the Gulf of Mexico)
Pregnant women are not eating enough fish, according to an FDA analysis. Data based on some 1000 women found that 21% had not consumed any fish in 1 month and 75% ate less than 4 oz. a week.