Up till now little attention has been given the exploitation of marine by-products from the fishing industry. Calcium in fish is found mainly in bone and skin. By-products from these sources are limited to production of gelatine. Small fish, which can be eaten whole with bones included, are traditionally considered to be a good source of calcium. Until recently, bioavailability of this calcium was not known. Two recent studies from Denmark have shown that the absorption of calcium from small soft-boned fish was comparable to that of skimmed milk both in rats and in humans.