OBSERVATIONS ON THE TERRITORIAL BEHAVIOUR OF JAPANESE MAJARRA, GERRES OYENA (FORSSKAL), IN THE VICINITY OF SETO

Abstract

1. Observations on the territorial formation in Gerres oyena were conducted by snorkelling from December 1, 1975 to January 25, 1976 on the protruded rocky reef near the Seto Marine Biological Laboratory. 2. Eight individuals were identified by natural blemishes on their body surface and such sighns were proved to be effective enough to recognize them one another for a considerably long time. 3. Three types of social organization were defined in this fish; i.e. aggregation, band and territory. 4. The territorial formation seemingly progressed in smaller individuals as: in aggregation→in band→domiciliation at cretain position in band→aggressive only against smaller comrades (partial territory)→against all conspecific individuals. 5. Observations of territory formation in the morning and territory release in the evening indicated that territorial owners went down to join the aggregation that was formed in the deeper layer and, in some cases, might migrate (inshore?) at night. 6. No hierarchy was observed in this fish, though the "nip order" between the band members, still struggling for territories, might be regarded as representing a hierarchy. Anyhow, this is far from the social organization and rather referred to the matter prior to the domiciliation.