Title Biological aspects of herbivorous fishes in the coastal areas of western Japan
Authers Atsuko YAMAGUCHI
Citation Bull. Fish. Res. Agen. No.32, 89-94, 2010
Seaweed beds in Japanese coastal waters have significantly declined in recent years, and feeding by herbivorous fish has been identified as one of the potential causes of this decline. In the western coastal areas of Kyushu, seaweed consumption by fish species such as the mottled spinefoot, Siganus fuscescens, sea chubs, Kyphosus spp, and the Japanese parrotfish, Calotomus japonicus, has become a matter of concern. Our study group has been investigating the biological aspects of herbivorous fish in the coastal waters around western Kyushu and Okinawa. In this paper, I introduce some of the results of my work focusing on the biology of herbivorous fish, including their distribution, feeding, and behavioral ecology. Investigation of the stomach contents of herbivorous fish revealed that K. bigibbus fed mainly on Sargassum throughout the year. In contrast, other fish supplemented their diet of seaweed with amphipods and other organisms. Experiments to determine food preference were performed on captive K. bigibbus, and their results supported the results of the stomach-content analysis. Both experiments showed that the fish selectively fed on Sargassum fusiforme and Undaria pinnatifida. Herbivorous fish off the west coast of Kyushu were tracked using a biotelemetry method. The fish inhabited seaweed beds during the daytime. The activity of S. fuscescens and K. bigibbus markedly declined when the water temperature decreased to approximately 20℃and 17℃respectively. It was observed that these fish overwintered in these areas. This study demonstrates that the recent rise in winter ocean temperatures has extended the period of activity of herbivorous fish. The results contradict the hypothesis that herbivorous fish species migrate northward during warm periods.
URI http://www.fra.affrc.go.jp/bulletin/bull/bull32/89-94.pdf