Humans were eating fish and shellfish long before they started cultivating plants or domesticating animals for food.
Shellfish are hard-covered , edible, mostly marine animals from two groups: the mollusks (oysters, clams, mussels) and crustaceans (crabs, lobsters, shrimp).
Fish and shellfish contain high quality protein with all the essential amino acids like red meat and poultry.
It is also low in fat and most of the fat it has is unsaturated.
Although shellfish have less oega-3 than the fatty fish, shellfish are still very good sources, better sources than the leaner fish. Shrimps, oyster and mussels are the leaders of the pack.
Generally, shellfish contain the usual amounts of cholesterol as found in meat.
Fish for human use produce largely by fish farming. It may be that the situation is beginning to change.
In some countries, several freshwater species (catfish, carp, trout, and tilapia) have been raised as a commercial enterprise for some years and milkfish have been raised for many years in the Philippines.
Oysters are now grown commercially in some areas, and the raising of shrimp in Japan is already commercialized.
Nutritional value of fish and shellfish