Abstract
Ovarian development and fecundity of the Oikawa, Zacco platypus, were studied based on 1, 562 specimens collected during one year from September 1965 in the water of the River Aki, Tokyo-to.The results of the study may be summarized as follows.1) Ovarian development was noted significant from April to June, accompanied by marked increase in body weight.2) The fecundity, number of large eggs counted in ovary, increased proportionally to the approximate third power of the total length.3) Estimated potential egg deposition (Hartman and Concle, 1960) per 100 females was about 38, 000 eggs for Zacco platypus cast-netted in June 1966.4) The reproductive potential gradually decreased during the spawning season;about 24, 000 eggs in July and about 9, 000 eggs in August.
