Exposure to contaminants in fish you eat may not increase your cancer risk at all, but it never hurts to be cautious. Fish species differ in diet, habitat, growth rate, and physiology, so different types of fish accumulate contaminants at different rates. Long-term effects of human exposure to contaminents have not been fully determined by health experts. Mercury for instance, is tightly bound to proteins in all fish tissue, including muscle. There is no method of cooking or cleaning fish which will reduce the amount of mercury in a meal.
Fish absorb PCBs from water, suspended sediments, and food.
PCBs concentrate in the fat of fish and particularly in fatty fish such as carp and catfish. Cleaning and cooking a fish to remove fat will lower the amount of PCBs you ingest. Larger, older fish, and fish which eat other fish, accumulate more contaminants than smaller, younger fish, which eat less contaminated prey. Carp multiply rapidly and have few natural enemies and therefore live longer than most other species of fish. Not everyone who fishes or who eats fish is at risk, and there are methods of reducing such risks.