メジナ幼魚の群れ生活

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Excellent studies on the social structure of fish in relation to territoriality have been done with Plecoglossus altivellis by MIYADI et al. In marine fishes, however, territoriality is very scarce in comparison with schooling habit. This paper records of the schooling habit of young Girella punctata, a common reef fish along the Japanese coast. Diving observations were performed in summer of 1955 at a reef near the Seto Marine Biological Laboratory of Kyoto University. The feature of the station is shown in figure 2. Young individuals feed actively in the daytime, and stay in shallow water near the coast at night. In the morning, they form large schools and do not feed at this time. But in daytime, schools are divided into smaller groups and they begin to feed actively (Fig. 2). In a school, all individuals of this species swim in the same direction and show the same behavior. On the other hand, the school is unstable, i. e., separation and fusion of schools are very common (Fig. 4). There are no structures as social hierarchy or leadership as are observed in mammalian herds. The territorial behavior of this fish may be seen in a tide pool. but a greater part of its life is maintained as a member of a school in the open sea. It is only by chance that the young of this fish remains in a tide pool. Thus, the territorial life of this fish has no important meaning to the natural life.
1956-12-31