ECOPHYSIOLOGICAL ADAPTATIONS EXIST IN NUTRIENT-REQUIREMENTS OF FISH - TRUE OR FALSE

1. Differentiation of digestive tract morphology in fish manifested by the lack or presence of a stomach, an extended intestine or enlarged intestinal surface frequently do not match feeding habits. 2. There is contradictory information regarding the effect of dietary substrates as potentiating the production of enzymes in fish digestive tract. 3. Quantitative requirements of essential nutrients seem consistent between fish species across various taxa and of varying feeding habits. 4. A concept of nutrient requirement being related to adaptation in the food characteristics as a consequence of feeding habits has a limited use.