流れ藻に関する研究・流れ藻に伴う稚仔魚-II

昭和33年度の津屋崎附近における調査

抄録

Although much attention has been paid to the fishes accompanying floating algae in the daytime, so far as is known, no study has been made of those at night. This paper is concerned with the relation between the life of fishes and the floating algae during night as well as day.
The authors obtained larvae. and juveniles of fishes accompanying the floating algae at night as well as in the daytime. They also collected fishes under a 1-kilowatt lamp at night, independent of algae. Collections were made during April, 1958 to March, 1959, in the vicinity of Tsuyazaki, Fukuoka Prefecture, by mean of a rectangular scoop net and dip nets. The results are given in Table 1. In the case of day collections, the floating algae drifting near the rectangular route as shown in Fig. 1 were scooped up. In the case of night collections, the authors left port thirty minutes before official sunset, and slowly proceeding searched for the floating algae with the help of lamp. The lamp was held at the bow, light-ing the water surface within about thirty meters. At certain locations the boat stopped with the lamp hung on the side of the boat for collecting about an hour.
Species and size ranges of fishes obtained from the floating algae at night were similar to those obtained in the daytime. In Oplegnathus fasciatus and Dasson trossulus from the night collecting the characteristic yellow coloration of their bodies was not revealed, and the blackish patterns on whitish ground color were clearly seen. Aluterid fishes did not show any noticeable color change. Most of the species collected under the mere lamp light were different from those accompanying the floating algae. In the few species caught both under the mere lamp and under the algae, differences in size and color patterns were observed. The majority of the juveniles appeared under the lamp light were those living near the surface, and some species among them were also obtained with the floating algae. This fact can be understood that those grown juveniles only temporarily used floating algae as their habitat in place of the algal zone in shallow waters where they were to live after the change of habitat in their life history.
Number of individuals as well as of species in the collections varied in seasons. Fish were abundant during spring to early autumn and scarce in winter. The largest number of species, 17, was obtained in early August, and the least number of species, 3, in October and in early February. Sebastes spp. were found in abundance from mid-April to mid-May. Late May yielded large catch according primarily to the abundance of Seriola quinqueradiata and Girella punctata in the collection. Dasson trossulus and aluterid fishes were taken in abun-dance during July to December. The largest number of individuals was collected in early September, represented by but 6 species. Girella punctata and Agrammus agrammus dominated from February to early March, but total number of individuals was rather few.