Sciaenidae are a family of fish commonly called drums, croakers, or hardheads for the repetitive throbbing or drumming sounds they make. The family includes the weakfish, and consists of about 275 species in about 70 genera; it belongs to the order Perciformes. A sciaenid has a long dorsal fin reaching nearly to the tail, and a notch between the rays and spines of the dorsal, although the two parts are actually separate. The anal fin usually has two spines, while the dorsal fins are deeply notched or separate. Most species have a rounded or pointed caudal fin. The mouth is set low and is usually inferior. Their croaking mechanism involves the beating of abdominal muscles against the swim bladder. They are small to medium-sized, bottom-dwelling fishes living primarily in estuaries, bays, and muddy river banks. Most of these fishes avoid clear waters, such as coral reefs and oceanic islands. They live in warm-temperate and tropical waters and are best represented in major rivers in Southeast Asia, northeast South America, the Gulf of Mexico, and the Gulf of California.