Nutrition and feeding influence growth, reproduction, and health of fish and theirresponse to physiologic and environmental stressors and pathogens. The basics offish metabolism are similar to those of warm-blooded animals in that they involvefood intake, digestion, absorption, and transport of nutrients to the various tissues.Fish, however, being the most primitive form of vertebrates, possess some distin-guishing features, such as the absence of a stomach in certain species, lack ofmandibular teeth, and nondifferentiated small and large intestines. Some major phys-iologic and metabolic differences between other vertebrates and fish include themechanisms involved in intestinal cell wall absorption by pinocytosis, metamorphosisin larval fish development, and the shift in osmoregulation in salmonids during seawater adaptation, carbohydrate metabolism, nitrogen excretion, and skeletal develop-ment. Unlike warm-blooded animals, which are homoeothermic, fish are poikilo-thermic, so their body temperature and metabolic rate depends on the watertemperature. Environmental temperature influences energy expenditure and nutrientintake. At low temperatures, the cell membranes of fish remain fluid because of theincorporation of high amounts of polyunsaturated fatty acids from dietary fish oilsand other lipid sources. Many fish efficiently use protein and lipid for energy ratherthan carbohydrates. Fish are also unique among vertebrates in their ability to absorbminerals not only from their diets but also from water through their gills and skin.
Nutrition, Feeding, and Behavior of Fish (PDF Download Available). Available from: https://www.researchgate.net/publication/24253536_Nutrition_Feeding_and_Behavior_of_Fish [accessed May 10, 2016].