Feeding habits of the California kilUfish, Fimduhis parvipinnis Girard, <br /><br />in Marina del Rey were examined relative to season and prey availability. Tem- <br /><br />poral changes in diet coincided with ontogenetic shifts in foraging habitats. Ju- <br /><br />venile fish fed selectively on relatively rare planktonic harpacticoid copepods and <br /><br />surface dwelling insects, whereas diets of adults were dominated by benthic prey <br /><br />taxa, principally tanaids. The seasonal availability of some prey taxa and the active <br /><br />selection of others associated with a particular foraging habitat affected the type <br /><br />and size of prey consumed. Our results indicate that patterns of prey use are not <br /><br />simple responses to seasonal changes in prey abundance.