Water Cod, Long Cod is not cod at all, they belong to the order of perch, the scientific name is called isoscale snake mackerel, commonly known as oil fish. Fat content is much higher than the real cod, not easy for human digestion. Oil fish in foreign countries is basically used for industrial purposes, industrial oil refining. In the United States, Japan, Australia, etc. is expressly prohibited from importing and recommended not to eat oil fish. The European Union, the United Kingdom, Singapore, Hong Kong, China, announcements require that oilfish be clearly labeled on the product, not to be confused with similar cod, misleading consumers, and labeled with the possible risks of consumption. However, China does not have a clear regulation related to the consumption of oilfish.

When cooking, cod (or oilfish) should be boiled or stewed for a while longer than regular fish because of its high fat content, and baked to minimize the potential risk of diarrhea. Silver cod, on the other hand, has a lower fat content and is better for braising