Bioaccumulation concentrates more pollutants the higher up the food chain you go. It is part of why most meat we eat comes from vegetarian animals. The fish we eat are often predatory so common advice is the keep the smaller and younger ones that are still big enough to be worth filleting. You don’t actually want to eat a trophy sized fish because they’ve accumulated more pollutants. Trophy sized fish are better off being realsed, they are often good breeders and help keep healthy population numbers.