魚の摂餌に関する生態学的研究-VIII

投餌回数と成長との関係

抄録

It has been found¹⁾ that the daily ration changes with frequency of feeding. From this it is natural to presume that the growth of fish changes with the frequency of feeding. In the present investigation, the relationship between the frequency of feeding and the growth is examined and the optimum frequency of feeding which produces maximum growth is discussed.
In the feeding of a school of fish, the daily rate of growth (mean increase in weight per day/body weight) can be expected to approach its maximum value when the daily rate of feeding (mean ration per day/body weight) reaches its maximum limit. However, if the daily rate of feeding is gradually increased, the gross efficiency of food conversion (daily rate of growth/daily rate of feeding) does not increase proportionately but increases so as to approach a maximum value. If the frequency of feeding is increased, the daily rate of feeding increases as an exponential function, and the daily rate of growth is roughly proportionate to it, resulting in the above stated condition (Table 1 and Fig. 1). This fact indicates that an excessive increase in the frequency of feeding in fish culture is meaningless. From the viewpoint of both labor and time continuous feeding will he impractical. Even though this is possible, the question of water pollution caused by excess food will arise. Consequently the question returns once again to the optimum frequency of feeding to obtain the largest growth rate. Taking the maximum value of the daily rate of growth as a standard and calculating the optimum frequency of feeding coinciding with 90% of the former, we have for filefish (fed short-necked clam meat) 2-3 times, puffer (fed jack mackerel meat) 2-3 times, yellowtail (fed jack mackerel meat) 1-2 times at about 22°C. Rainbow trout (fed compound feed) 2-3 times at about 12°C (Table 4).