Diversity in the ecosystems of Lake Tanganyika and Lake Biwa

点击翻译按钮获取中文摘要

Between the end of September, 1994 and the end of January, 1995, three Japanese researchers and one Zairean researcher, Department of Fisheries, Mpulungu, Zambia, which locates the southernmost end of Lake Tanganyika, to conduct cooperative research of Lake Tanganyika between Japan and Zaire. Since implementation of the research in the Zairean and Burundian water was not possible for inter-tribe battles, the research was done in Zambian water, with cooperation with Zambian fisheries research officers at Mpulungu.The purpose of the research is to elucidate the mechanisms to maintain the fascinating biodiversity of Lake Tanganyika. Social structure, feeding behavior and geographical morph variation of algal feeding herbivorous cichlid fishes were studied in rocky littorals near Mpulungu. Distribution of Atyidae prawns was also studied in the rocky littoral area.Territoris of the genus Petrochromis species were maintained against congeneric fish. Their territories were occupied compactly … More almost all area of shallow rocky littoral. Males of Petrochromis polyodon occupy their territory neighboring with conspecific females or smaller congeneric fish, but never occupied territory with conspecific males side by side. When a male of P.polyodon was removed experimentally, its territory was taken over by the nearest conspecific male by expansion or a new immigrant of conspecific male, but never occupied by the neighbor nor a new immigrant of other congeneric species. This result suggests that intraspecific male-male aggression of P.polyodon is responsible for the maintenance of territory separation, and furthermore interspecific small habitat separation seems to facilitate coexistence of other congeneric species.Algal feeder cichlids of other genera can come in and feed on attached algae on stone in the territories of Petrochromis fish. It is hypothesised that they are permitted by Petrochromis fish by using different resource of algae which Petrochromis fish do not use. In this hypothesis underwater observations of the feeding behavior of the genera Telmatochromis and Simochromis fish were made. Fish collection of these genera were also made. Analyzes of feeding habit and mouth morphology are underway.Atyid prawns are important food organisms for benthivorous cichlid fish. Distribution of atyid prawn in the littoral rocky area was studied by pulling a net, setting traps and scooping a dipnet underwater. Analysis of the collecting specimens is underway. Less