We investigated the feeding ecology of tilapia (Oreochromis spp) in the Salton Sea. Stomachs and intestines were sampled at each season. Fish foraged at the surface during the summer when dissolved oxygen was low. The proportion of plant materials in fish stomachs was higher at river mouth areas. Diatoms dominated the phytoplankton; rotifers were dominant during the spring and summer; copepods were dominant during the fall; barnacle larvae dominant during the winter. Pile worms (Neanthes succinea) were present throughout the year. Feeding activity was reduced in the summer, when dissolved oxygen was low and water temperature high.