The eel, also called the rice field eel , has a slender body and a snake-like shape. The head is long and round. The mouth is large, the upper jaw is slightly protruding, and the lips are quite developed. There are fine teeth on the upper and lower jaw and cranium. The eyes are small and covered by a thin skin. The left and right gill openings merge into one on the ventral surface, forming a “V” shape. The gill membrane is connected to the gill isthmus. The body surface generally has lubricating liquid for easy escape and no scales. There are no pectoral and pelvic fins; the dorsal and anal fins degenerate only with skin folds, no soft spines, and are combined with the caudal fin. In life, the body is mostly yellowish brown, light yellow or orange, with dark gray spots, and some eels are white, commonly known as “white eel”.