Ecological Studies on the Feeding of Fishes-IV

From the various conclusions arrived at in the previous reports1), 2), 3), if the satiation amount of a s0chool of fish is defined to be the amount of food fed until the fish can take no more, to obtain a constant value for the satiation amount the following two points at least can be considered as being important basic factors or prerequisites. 1) Acclimatization A school of fish does not take to food well immediately after liberation in the experimental tank. However, as time passes the satiation amount increases gradually each day until it reaches a constant value. As a result, a relatively constant value for the satiation amount can be obtained with a well acclimatized school of fish. 2) Hunger The satiation amount of a school of fish depends on the degree of hunger. As the time of food deprivation increases, the satiation amount first increases and then levels off to a constant value. As the stomach contents approach zero, the satiation amount reaches its maximum. Consequently, if the satiation amount is obtained when the stomach is completely empty, a value with very little fluctuation can be expected. In the present investigation, by standardizing the satiation amount in the above method the change of the amount of food consumed with time is examined and the satiation curve obtained. From the result, the accumulative amount of food consumed increases rapidly at the beginning; the rate of increase declines with time and subsequently reaches a constant or the satiation amount (Fig. 1). The satiation curve can be expressed by the formula: F=ktnwhere F=accumulative amount of food consumed (grams), t=time (minutes), and k and n=constants. These constants obtained are shown in Table 3.