広島県東広島市小田山川のカワニナ殻径頻度分布 The frequency distribution of the shell diametere of Semisulcospira libertina (Gould, 1859) living in the Kodasan-river in Higashihiroshima-shi, Hiroshima Prefecture

The frequency of the shell diameter of Semisulcospira libertina (Gould, 1859) which inhabits the Kodasan-river in Higashihiroshima-shi was studied through one year. The prosperous time of the production from the appearance of newborns, the average value of the shell diameter, and the median of the shell diameter is from February to April. The life span of this species in this area is presumed to be about two years. Through a year, the average shell diameter of this species is about 4mm to 8m, and the large individuals of this species were obserbed well in October.

The frequency of the shell diameter of Semisulcospira libertina (Gould, 1859) which inhabits the Kodasan-river in Higashihiroshima-shi was studied through one year. The prosperous time of the production from the appearance of newborns, the average value of the shell diameter, and the median of the shell diameter is from February to April. The life span of this species in this area is presumed to be about two years. Through a year, the average shell diameter of this species is about 4mm to 8m, and the large individuals of this species were obserbed well in October.