Why not buy farm raised fish?
They have always been found to have higher levels of toxin and PCB's due to what they are fed. Google it and you will find numerous articles and research studies done on the topic. Although there seems to be farmed raised organic fish which may be fed a different diet to eliminate the toxin levels found. Also keep in mind that this is for salmon, but nonetheless all farm raised fish have a similar diet. See below (a little older, but most quote his studies):
Is farm raised fish safe???
Studies suggest farmed salmon may be far from pure. A recent pilot study by Canadian scientist Michael Easton, an expert in ecotoxicology, found that a four-fish sample of farmed salmon when compared with wild-caught salmon contained elevated levels of chemical contaminants, including PCBs -- known carcinogens.
Easton's research, which was published in the peer-reviewed international science journal, Chemosphere, showed 10 times more PCBs in farmed salmon than in wild fish -- levels that he believes pose a health risk for regular consumers.
Levels of pesticides in farmed fish were also significantly higher, Easton's study showed, while mercury levels were roughly the same. ''This is a preliminary study that raises significant questions,'' Easton says.
He stresses the possibility of damage to anyone who consumes farmed salmon directly or indirectly from combined, low-level toxins. Easton also points out the elevated risk of mental retardation and brain damage to nursing babies and unborn fetuses.
Other new studies in the United Kingdom (source of many farmed salmon that supply U.S. markets) have cast further doubts on the safety of these fish, enough to fan an outcry in the British media.
A recent feature in the Daily Mail outlines a ''chemical cocktail'' of substances found in trace amounts in these fish, including canthaxanthin, a dietary additive that gives farmed salmon its appealing color; various pesticides such as cypermethrin, dichlorvos and azamethiphos, associated with cancer and reproductive problems in humans; copper and zinc-based paints; and malachite green, a fungicide. The latter was banned in June by the Scottish government, and a European government-sanctioned science commission has recently called for a two-thirds reduction in canthaxanthin, which has long been banned by the European Union for direct human consumption, due to its potential for vision damage.
The contaminants' source is linked to the farming process. PCBs and other toxins are concentrated in the oil-rich, pelletized fish meal, which farmed salmon are fed. The fish are treated with pesticides to control parasites, fed canthaxanthin and subjected to pen disinfectants. Antibiotics are administered to treat disease in crowded pens. In addition, there is mounting evidence farmed salmon contain fewer of the beneficial omega-3 fatty acids for which wild salmon are so highly touted.
A number of respected sources, including U.S. nutritionist Andrew Weil and The American Journal of Clinical Nutrition, state that farmed salmon have two to three times fewer omega-3's than their wild counterparts. Meanwhile, the fat content of farmed fish ranges between 11% and 20% vs. 7% for wild.
There are serious environmental issues associated with salmon farming as well. The spread of highly infectious, mutating salmon diseases, large-scale environmental pollution and the escape of millions of non-native fish from salmon-farm operations are all ongoing problems that alarm scientists. They worry about the potential impact on wild salmon stocks.