Eels (Anguilliformes) are an order of fish which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators. The term 'eel' is also used for some other similarly shaped fish, such as electric eels and spiny eels, but these are not members of the Anguilliformes order. Eels are elongated fish, ranging in length from 5 centimetres (2.0 in) in the one-jawed eel (Monognathus ahlstromi) to 4 metres (13 ft) in the slender giant moray. Adults range in weight from 30 grams to well over 25 kilograms. They possess no pelvic fins, and many species also lack pectoral fins. The dorsal and anal fins are fused with the caudal or tail fin, forming a single ribbon running along much of the length of the animal. Most eels live in the shallow waters of the ocean and burrow into sand, mud, or amongst rocks. A majority of eel species are nocturnal, and thus are rarely seen.
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