The study was carried out in a controlled environment, for 35 days, on the production responses of octopuses when fed exclusively and alternatively with the prey species included in their natural diet: crustaceans, molluscs and fish. Three experimental groups were established, and given a monodiet of crab (Carcinus mediterraneus: Group C), tattler (Illex coindetii: Group T) and fish (Mugil cephalus and Sardine pilchardus: Group F), respectively, 'ad libitum', 3 times a week (3 pairs of octopuses for each experimental group). Crab was captured in markedly greater quantities than fish and tattler and the subjects fed on this food displayed the best pattern, reaching a higher final weight, corresponding to a significantly greater increase than in Group F. The superiority of crab mainly seems to depend on the fact that food intake is higher than for tattler and fish. However, all the foods used during the trial were well accepted by the octopuses.