ハモ属の資源生物学的研究-II

Abstract

It is very important to investigate the feeding habit of fish in order to make clear a section of fish ecology. Accordingly, the author has been engaged in the study of the feeding habit of Muraenesox cinereus since April 1951. The fish dealt with here was collected from Fukuoka Fish Market between April, 1951 and August, 1952 and from March, 1953 to December, 1953. Their stomach weights were measured and the contents examined. The results obtained are as follows. 1. The teeth of M. cinereus are very sharp and suitable for attack on the food animals. The fish are voracious and their liver are rather large. 2. The number of fish whose stomach contents are recognizable is generally a little larger between July & Sept. than other seasons but this frequency does not show a definite trend in relations the size of the body. 3. All of the foods are animal material and various as to species. Generally speaking, crustacea amount to 45.2%, fish to 36.3% and mollusca to 18.5%. 4. In relation to the body length, a) Crustacea decrease from about 63% to 13%, while. b) Mollusca gradually increase from about, 3% to 32%. c) The fish preyed are almost invariable under 400mm in body length, but increase from about 33% to 80% immediately over 400mm. 5. The composition of stomach contents varies as shown in Fig. 3 which is illustrated by triangular graph in a year. Further, the feeding habit of the fish varies according to the size of body, but no abrupt change occurs annually. 6. Among the food animals, the crabs are greatest in quantity, then the lobsters, squids, octopus and squills follow. Platycephalus indicus, Cynoglossidae and Trichurus haumela also attract M. cinereus, but the author does not think that the latter selects the fish species especially. 7. The logarithm of stomach weight increases in proportion to the enlargement of that of body length.