Crayfish are freshwater crustaceans of the order Decapoda, which includes crabs, shrimps, lobsters, and hermit crabs. Crayfish are found on all continents on Earth except Africa and Antarctica. They are an essential part of the food chain. They feed on algae, insects, mussels, and snails, while fish, herons, otters, and other larger animals feed on them. This feeding balance has been maintained for hundreds of thousands of years. Unfortunately, people destroy this balance.
Crayfish evolved from marine ancestors dating back some 280 million years. There are more than 300 species of crayfish worldwide. Although nearly half of the species are endangered or imperiled. They live in water, hiding beneath rocks, logs, sand, mud, and vegetation. Some species dig burrows.