The butter fish is popularly known as the leather jackets or the queen fish. It is closely related to the pomfret and the Horse mackerel. The body is compressed and clothed with moderate sized scales. The anterior dorsal fin is composed of a few free isolated spines. The teeth are well developed. As the skin is thick and can be easily peeled off, these fishes are known as Leather jackets. The colour during life is silvery on the sides, with a row of circular blotches above the lateral line. The median fins are dark. These fishes follow shoals of the white bait and other small fishes and prawns on which they feed. Chorinemus lysan especially attains a large size reaching a length of four feet.

   The eels, which are long, snake-like fishes, often growing to a large size. The body is elongated, cylindrical or compressed and band-shaped. Eels are voracious fishes occurring in the tropical and sub-tropical seas and are especially abundant in the crevices of coral rocks on reefs. In many species, the jaws are curved and the mouth is filled with the knife-like teeth, that the jaws cannot be closed. The teeth are well adapted for holding their slippery prey. Eels are catadromous fishes, i.e., they return to the sea to breed. They are well marked with fine, dark spots on the head and the body.