Narrow cod is not oily fish. It can be distinguished from the following five aspects: First, fish scales. Cod has small scales and small silver spots on its body. The fish scales are very sharp and feel like needles, but the fish scales of oily fish do not have this feature. The second is body color. Cod has a variety of body colors, from light green or light gray to brown or light black, and from dark red to bright red. The head, back and sides are grayish brown with irregular dark brown stripes, and the ventral surface is grayish white. However, the body color of oily fish is black or bluish-black, the ventral surface is grayish white, the fins are slightly black, and the body scales have black edges; The third is meat color and meat quality. Cod has large cross section, white skin, white meat without obvious thick red line, and tender meat. However, the cross section of oily fish is small, the skin is gray-black, reticulate, the meat is yellow with yellowish or reddish lines, and the meat is hard and rough; The fourth is the feel. After the cod is thawed, it will feel smooth, like a mucus film. Oil fish feels rough, not as smooth and tender as cod; The fifth is the taste. Cod meat is very delicate, has a unique flavor and umami flavor, and tastes excellent. However, oily fish tastes greasy, and its meat quality is rough and its taste is poor after cooking.