Abstract
Environmental conditions of egg deposition sites of wild minami-medaka Oryzias latipes were investigated in an aquatic area of a biotope in order to obtain basic information for conservation of wild Japanese medaka species in danger of disappearing. Deposited eggs were observed mainly at the banks of shallow streams where the flow rate was below 1cm/sec. Eggs were also observed in the fallow paddy field. Few eggs were observed in the deep streams and the ponds. Eggs were mostly deposited on relatives of Genus Spirogyra, fresh water algae, as a substrate. The deposition sites were situated at the depth of 0 to 15 cm in water.
