What direct correlation exists between a fish's physical characteristics and potential toxin levels like mercury or PCBs?

Toxin levels tend to correlate directly with the fish's size and age, as larger, older fish accumulate more potential toxins through bioaccumulation.

Public health advisories regarding contaminants such as mercury or PCBs are strongly linked to the biological processes within long-lived organisms. Bioaccumulation is the mechanism where toxins are retained and increase in concentration over time within an organism. Since larger fish are generally older and have consumed a greater quantity of contaminated prey over their lifespan, they serve as effective accumulators of these persistent environmental toxins. Consequently, health warnings often specifically target larger individuals within a species because they pose a higher risk profile compared to their smaller, younger counterparts, making size and age primary indicators for assessing personal consumption risk.