Reciprocal diet switches were conducted with first-feeding white sturgeons Acipenser transmontanus to investigate possible mechanisms of food acceptance and food preferences. Survival and relative growth rates were significantly reduced following a switch from a more natural diet (chopped Tubifex sp. worms) to a prepared diet (Biodiet), whereas growth was improved, and survival was improved or unaffected, following the reciprocal diet switch. Feeding observations, followed by assessment of stomach fullness, indicate that strong or exclusive preferences for Tubifex can develop quickly. These data suggest that the animals are more “prepared” physiologically and anatomically to accept and assimilate the more natural diet than the prepared diet during the early life stages. Associative learning of pre- and postingestional stimuli may be important in the development of food preferences.