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. Because contaminants may produce harmful effects when consumed over a period of time, humans are advised to limit the amounts of the riskier types of fish in our diet. PCBs and mercury build up in our bodies over time.
Humans excrete mercury from our bodies, but that process also takes time.
Therefore, it is important to regulate our meals of fish that are susceptible to contamination. Space such meals out over several weeks or months. It may take months or years of regularly eating contaminated fish to accumulate levels which would be a health concern. If you carefully follow the fish advisories when posted, carefully prepare and cook the fish, and limit the size and number of fish you eat, the amount of mercury you take into your body will have time to be safely eliminated between meals. People who regularly eat sport fish, women of childbearing age, and children are particularly susceptible to contaminants that build up in the body over time.