Generally, the amount of product that is obtained from the raw material. Of most interest in fish technology is the yield of edible material. Typical yields of edible meat from some major groups of fish are: vertebrate fish, as skinless fillets 40% , shrimp and prawn 45%, crab 30%, bivalve shellfish 15%, cephalopod 70%. Within these groups, yields vary with species, and within species with size, season, and condition. W(omega)-3 fatty acids, w(omega)-6 fatty acids An alternative naming system for polyunsaturated fatty acids (PUFAs). The w carbon atom in the molecule is that of the terminal methyl group corresponding to n in the other system so w-3, for example, refers to the position of the first carbon atom counting from the terminal carbon, the third in this case, attached to a double bond.