Studies on the Daily Rhythm of Feeding Activity in Fish, Especially in Goldfish, Carassius auratus (LINNÉ)

Daily rhythm of the feeding activities in fish was investigated in order to know the fundamental aspects of fish behavior and to apply those to the practical measure of fish cultivation. Six types of automatic feeding recorders were devised. Especially, a waterproof type of contacting tube was designed for both laboratory and field uses. Spawning behavior in goldfish was also recorded by modifying the field type of the recorder. Seven fresh-water and twelve marine fishes were used for examining the daily rhythm of feeding activity, and the three types of the feeding rhythm were classified. (1) The diumal rhythm of the feeding activity was found in Carassius auratus (LINNÉ), Cyprinus carpio LINNÉ , Epinephelus fasciatus (FORSKÁL), Girella punctata GRAY, Halichoeres poecilopterus (TEMMINCK et SCHLEGEL), Mylie macrocephalus (BASILEWSKY), Oryzias latipes (TEMMINCK et SCHLEGEL), Siganus fuscescens (HOUTTUYN) and Stephanolepis cirrhifer (TEMMINCK et SCHLEGEL). (2) The typical nocturnal rhythm of the feeding activity was found in Parasilurus asotus (LINNÉ) and Triakis scyllia MÜLLER et HENLE. (3) Anguilla japonica TEMMINCK et SCHLEGEL, Fugu rubripes (TEMMINCK et SCHLEGEL), F. poëcilonotus (TEMMINCK et SCHLEGEL), Gonistius zonatus (CUVIER et VALENCIENNES), Oncorhynchus keta (WALBAUM), Salmo gairdnerü irideus GIBBONS and Trachurus japonicas (TEMMINCK et SCHLEGEL) did not show any distinct daily rhythm, at least in the present experiment, though the cultured specimens of O. keta and S.g. irideus were found to be diurnal. Analytical experiments on the rhythmic aspects were carried out using the goldfish “Wakin.” Effects of the population density on the feeding activity were examined using eight groups of the fish with 430 liters of water in a concrete tank. The growth rate of the fish reared with each group of 3 to 9 individuals in a tank was found to be relatively greater than the other groups examined. So, most of the experiments reported in this paper were carried out using those numbers of the fish per tank. Correlation between the feeding activity and climatic conditions was examined throughout one year and a half. Generally, goldfish showed an active feeding when the atmospheric pressure was upward. On the contrary, the feeding became inactive on a cloudy or rainy day, and almost no feeding was recorded on a stormy day. It was found that the solar radiant heat was one of the most influential factors on their feeding activity during summer. Water temperature appeared to be more effective than the other factors in the seasons of from autumn to early spring. The idea of inflection point, d^2T / dt^2, was introduced into the analysis of temperature stimulus to the fish in these seasons. The peak of the feeding activity in a day was found to correspond approximately to this inflection point which was found to occur in a few hours before maximum temperature recorded