抄録
Studies on the sterility of triploid ayu were performed and its potentiality was evaluated, with the aim of eliminating some of the current difficulties of ayu culture and increasing culturing efficiency. Triploidy was induced by cold-shocking the eggs shortly after insemination. Observations of triploid ayu in the spawning season revealed the following facts. Each triploid shows no gametogenesis, because of its underdeveloped gonad. Most of the triploids show no secondary sexual characters and the edible portion of the triploid ayu is larger than that of the diploid. These results indicate that the production of triploid ayu is highly effective for the following purposes: 1) to lengthen the trading period of ayu as a commodity by extending the one-year life-span (diploids die after spawning), 2) to prevent the reduction of commercial value which is caused by the occurrence of secondary sexual characters and 3) to breed more profitable fish as edibles.
