 An example, which has caused much trouble in Maryland and Florida, is the snakehead fish.Predatory fish such as sharks, mahi-mahi, billfish, and tuna form a part of the human diet, but they tend to concentrate significant quantities of mercury in their bodies if they are high in the food chain, especially as apex predators, due to biomagnification.Predators are an important factor to consider in managing fisheries, and methods for doing so are available and used in some places.