Ecological studies on guppy, Lebistes reticulatus Peters, I : Acclimatized guppy in the waters of hot springs in Japan

Abstract

The authors confirmed that a aquarium fish of South America, guppy (Lebistes reticulatus Peters) has been acclimatized in the sewages of hot spring water of Rendaiji (N34°42′, E138°12′), Asama (N36°15′, E138°00′), Togura-Kamiyamada (N36°29′, E138°05′) and Uchigo (N37°02′, E140°51′) from several years ago. Regular surveys of the guppy populations and the enviromental factors of habitats were mainly made in Togura-Kamiyamada and Rendaiji. Water temperature of the habitats of guppies was maintained about 20℃ even in winter season. These guppies were not cold-resistant. They begin to disperse to irrigation streams, rice fields and shallows of rivers in summer. In one of the winter habitats population density of guppy attained to extreme high level until end of winter, but it remarcably decreased in summer as dispersion of fish proceeded. The guppies showed so rapid growth and so great fecundity that they could fill the summer habitats in shorter time. It can be supposed that guppy is suitable to be used as a predator of mosquito larvae which emerge in rice fields and other smaller water bodies by the reason of its euryphagy and rapid increase in number. In the rice fields of Rendaiji and Togura-Kamiyamada, very little larvae of Anopheles sinensis and Culex tritaeniorhynchus were discovered.