Abstract:Seventy years ago, the researches of fish nutrient and feed started and established their paradigm on basis of the paradigm of the researches on terrestrial animal nutrition and feed. In past seven decades, a great amount of data was generated and accumulated in the researches of fish nutrient and feed conducted under the paradigm, and application of these data promoted the development of technology and industry of aqua-feed production. However, aquaculture farming practices always arise ever-growing demand or standard to aqua-feed industry because the pressures of natural resource depletion and environmental pollution increased with the fast expansion of aquaculture industry in the world. Unfortunately, more and more facts indicate that formulated feed designed for some fish species on basis of the researches of fish nutrition and feed cannot be used in commercial farming practices of the fishes with the expected efficacy. These facts reveal that results of these fish nutrition and feed researches conducted under the current paradigm could not meet the demand of modern finfish aquaculture industry. In this paper, the author reviewed the researches about nutrient requirements and dietary fish meal replacement for largemouth bass Micropterus salmoides and large yellow croaker Larimichthys crocea, two carnivorous fish species commercially important for aquaculture in the world and China. The application of formulated feed in commercial farming of largemouth bass and large yellow croaker is full of twists and turns, and the fishes had to be fed with raw fish diet for a long period due to the fish fed with raw fish diet displayed faster growth relative to those of the fish fed with formulated feed. The poor growth of largemouth bass and large yellow croaker fed with formulated feed are attributed to obviously underestimated dietary protein levels. After reassessment of protein requirement, the optimal protein level was elevated from 400-440 g/kg to 480-510 g/kg in largemouth bass diet and 450-470 g/kg to 490-520 g/kg in large yellow croaker diet. Growth of largemouth bass and large yellow croaker fed with the formulated feed containing optimal protein content are comparable to that of the fishes fed with raw fish diet. The author indicates that the disadvantages in the current paradigm for fish nutrient and feed research include: (1) The current paradigm emphasizes the role of food in regulating fish growth, but ignores the importance of genetics background of the test fish and environmental conditions except food in determining growth and food intake. (2) The current paradigm emphasizes individual growth of the test fish in evaluating nutrient requirements and feed quality, but ignores the fact that the difference in individual growth of the fish cannot completely reflect the differences in yield and economic income of commercial fish farming. (3) The current paradigms emphasizes the importance of growth and feed utilization efficiency as indicator in fish nutrition and feed research, but ignores that the negative impacts of fed aquaculture on environment and natural resources are the bottle-neck limiting sustainability of aquaculture industry. (4) The current paradigm ignores the role of basal diet formula in evaluating nutrient requirement and feed quality, and the misapplication of unreasonable basal diet resulted in senseless or erroneous conclusion in some research. To diminish the disadvantages, the author proposed to shift the current paradigm as: (1) In concept and theory, emphasizing the importance of genetics background of the test fish and environmental conditions except food in determining growth and food intake, and emphasizing that fish growth determine nutrient requirement, while dietary nutrients modulating fish growth. Moreover, emphasizing the role of different feed ingredients in nutrient balance of diet formula. (2) In investigation method, emphasizing the importance of genetics background and population structure of the test fish used in feeding trials, and emphasizing the magnitude of individual growth as an indicator for assessing nutrient requirement and feed quality. On the other hand, emphasizing the impacts of dietary nutrient supplementation and feed quality on sustainability, such as environment friendship, fishery resource protection, and ecosystem services. The shifted or improved paradigm for fish nutrition and feed research is better in accord with the situation of commercial fish farming, and results of the research conducted under the shifted paradigm are more reliable and accurate for designing and producing quality formulated fish feed. The application of quality formulated feed can benefit to improve sustainability of commercial fish farming practices.