There are over 20,000 living species of fish. Many are brightly colored, and many have shapes and patterns that serve as camouflage. They are found in all marine, fresh, and brackish waters throughout the world and at all depths. Most are confined either to saltwater or to freshwater, but some are physiologically adapted to moving from one to the other. Fish may be carnivorous, herbivorous, or omnivorous.
Some fish are scavengers on lake or ocean bottoms.
Licensed from Columbia University Press.