Black herring, commonly known as green root fish, herring, herring, herring, long cylindrical, slightly sharp mouth, not necessary. Its back is black, its abdomen is milky white, its meat is white and full, and its thorns are big but few. Grass carp, commonly known as grass weeds, grass-roots fish, pomfret and grass green, is long, slightly cylindrical, slightly round at the mouth, unnecessary, with dark back, yellowish brown body, gray abdomen, tender meat and few thorns. The main differences between herring and grass carp are body color and mouth shape. Black herring has a black body and a slightly pointed mouth; Grass carp has a yellowish brown body and a slightly round mouth.