Male California sea lions have been known to assemble at the mouths of fresh water rivers where there is a steady supply of fish. California sea lions tend to feed alone or in small groups unless there is an large quantity of food. Under conditions of increased food supply, Zalophus californianus hunt in larger groups. Zalophus californianus have been known to feed cooperatively with cetaceans, seabirds and harbor porpoises. Often one species locates a school of fish and signals the presence of food to the other species. While rare, it has been recorded that California sea lions drink seawater while not breeding (Riedman, 1990).
Foods eaten include: cephalopods, anchovies, herring, Pacific whiting, rockfish, hake, salmon, squid and octopuses (Riedman, 1990).