The Order Anguilliformes, or true eels, contains 20 families and about 820 species.
Species are usually long and slender, with long-based dorsal and anal fins that are continuous with the caudal fin (if present) in all but one species. All species lack pelvic fins, and some groups lack pectoral fins. Scales are usually absent, or if present, are embedded in skin.
Most species are nocturnal and live in shallow waters, burrowing into sandy or muddy bottoms, or hiding in crevices, caves and holes on coral and rocky reefs.
Most true eels are predators and belong to one of three families: Congridae (Conger eels), Muraenidae (Moray Eels) and Ophichthidae (snake eels and worm eels). Families:Congridae 康吉鳗科 , Muraenidae 海鳗 , Ophichthidae 蛇鳗