The diet of Atlantic cod is best described as opportunistic because they feed on anything they are capable of capturing. At all life stages, however, they eat primarily other animals. During the larval stage they feed on smaller organisms such as zooplankton. Juveniles feed on shrimp and other small crustaceans. Adult Atlantic cod consume squid, mussels, clams, tunicates, comb jellies, brittle stars, sand dollars, sea cucumbers, and polychaetes, and are also cannibalistic. The choice of prey included in the diet seems to play a role in determining the skin color of cod. Those that feed on crustaceans tend to appear more brownish in color whereas a blue-green pigment may be the result of a diet consisting primarily of fish. ("Assessment and Update Report on Gadus Morhua (Atlantic Cod)", 2003; Riede, 2004)