Evaluation of the Hatching Efficiency of Ayu in the Incubation Channels
Proceedings of the International Symposium on Fishways '95
The Organizing Committee for International Symposium on Fishways '95 in Gifu
The present report summarizes the results of the hatching experiments in the incubation channels in 1994. Eggs and sperms were obtained from the mature adults collected in the Nagara River. Following the artifical insemination, one hundred million fertilized eggs were planned to be cultured up to the eyed eggs and transferred to the incubation channels. Theur survivals were to be monitored until their release. Hatching rates under the natural and experimental conditions were both suggested to be around 0.5, and those adjusted by the survival curves were thought to be 0.6. Instead of the one hundred million fertilized eggs to be collected, 33 million eggs were obtained as results of delayed spawning due to the limited experimental period caused by the increased water flow in the river. The overall average of the hatching rates was around 0.5, and it is suggested that some 16.5 million Ayu-fries have hatched out from about 33 million artificially fertilized eggs. It is shown that the Ayu-fries have hatched out from 5 p.m. to 9 p.m., especially around 6 p.m.