Fish oils and human diet.

Trends in global fish catches are described together with fish landings and fish consumption in the UK. The importance of n-6 and n-3 polyunsaturated fatty acids as essential constituents of human diets is considered and the role of oily fish as a dietary source of the long-chain n-3 polyunsaturates, docosahexaenoic acid and eicosapentaenoic acid, is emphasized. The origin of n-3 polyunsaturates in, the marine phytoplankton and their transmission via zooplankton to fish is described as a means of understanding the composition of different fish body oils. The ease with which the fatty acid composition of fish body oils can be manipulated by altering the fatty acid composition of their feeds is emphasized and the dietary requirements of marine and freshwater fish for n-3 and n-6 polyunsaturates considered. Farming fish on diets containing principally fish meal and fish oil, as used in salmon production in Scotland, generates a high quality product with levels of long-chain n-3 polyunsaturates equalling or exceeding those of wild fish. Farming fish on high quality marine oils rich in docosahexaenoic and eicosapentaenoic acids is an efficient means of delivering these essential nutrients in human diets and also efficiently exploiting a strictly limited marine bioresource.