Small-mouthed catfish is also called Silurus asotus, Silurus asotus, Silurus japonicus, pond lice, Silurus asotus, Huaizi, etc. Its scientific name is Silurus asotus, which is a fast-growing and small-sized economic fish in Siluridae, and is similar to Silurus asotus in appearance. It is widely distributed in China, with tender meat, less thorns and more meat, more fat and higher nutritional value. The food eaten by the weak, the elderly and the patients after operation has a good auxiliary effect on restoring physical strength, and the maternal food can promote lactation and increase milk.

Morphological characteristics: Silurus meridionalis has a long body and a flat side, generally 25 ~ 40 cm long, with a cylindrical front and a flat back. The head is flat, the kiss is short, wide and round, and the kiss length is significantly smaller than the back of the eye. The mouth is sub-superior, wide, arc-shaped, with well-developed lip folds at the corner, and the end reaches the vertical line of the anterior margin. The lower jaw protrudes slightly before the upper jaw, and the upper and lower jaws have villous fine teeth. Small eyes, eye spacing is smaller than the length of the back of the eye. There are 2 pairs of whiskers, and the maxilla must reach the end of pectoral fin. The fish body is naked, smooth and scaleless, and the skin is rich in mucus and has mucus holes. The lateral line is complete and straight, the dorsal fin is short, there is no hard thorn, and its starting point is closer to the snout than to the base of the caudal fin. The pectoral fin is fan-shaped and small, with saw-like hard spines. The ventral fin is small and the end exceeds the starting point of the gluteal fin. The base of the gluteal fin is very long, the starting point is close to the armpit of the ventral fin, and the back end is connected with the caudal fin. Fat-free fin, short caudal fin, slightly concave. The back and side of the body are grayish black or dark brown, the ventral surface is grayish white, the dorsal fin, gluteal fin and caudal fin are grayish black, and the pectoral fin and ventral fin are grayish white. Small individuals often have cloud patches.