Ecological Studies on the Feeding of Fishes-I

Satiation Amount as Indicator of Amount Consumed

Abstract

Recent research by Russian marine biologists under the title of “animal trophic ecology” has opened new areas for research covering ecological problems on the feeding of fishes (IVLEV¹⁾). These problems are important fundamental subjects for research from the viewpoint of both fish culture and fisheries. Particularly in fish culture, the amount of food consumed is related to the amount of food fed, the growth and eventually the harvest. Although much research has been devoted to the amount of food fed, however, the available data are insufficient to advance research on the amount of food consumed.
KARIYA^{2, 3)} published studies relating to the amount of food, in a single feeding or in a day, would satiate a school of fish, and the amount of growth expected from such feedings. He examined stomachless fishes such as the common carp and goldfish. In the present study the same problems are taken up mainly with stomached marine fishes. First, “satiation amount”, the amount of food sufficient to satiate a school of fish in a single feeding, is used as the basis for standardizing the amount of food consumed. Second, conditions affecting the satiation amount are examined. Finally, the relationships existing between the daily frequency of feeding and the satiation amount, and between growth and satiation amount, are examined.
The first problem encountered in experimentally determining the amount of food consumed by a school of fish is whether a constant value can be obtained or not. It is necessary to take up this problem and the pattern of the change of the amount of food consumed with time is examined. The result obtained is summarized as follows:
Since the amount of food consumed by a school of fish varies with time (Fig. 1), in attempting to obtain a constant value for the amount of food consumed it is necessary to feed the fish until the accumulative amount of food consumed reaches a constant value, or, in other words, the fish are satiated. If the fish are not fed to satiation, the value for the amount of food consumed will change with each feeding experiment and a constant value cannot be obtained. In this research, “satiation amount”, the quantity of food required to satiate a school of fish in a single continuous feeding, is used as the indicator of the amount of food consumed.