Natural spawning in the captive barfin flounder Verasper moseri, and estimation of the spawning time based on the embryonic development of the fertilized eggs

摘要

Low density culture, (0.24-0.26 ind./m-2) of barfin flounder, in large sized aquaria was undertaken to establish a culture system for stable procurement of the fertilized eggs. Captured females spawned repeatedly for approximately one month, and the total number of spawned eggs during a spawning season was averaged between 85,000 to 406,000 per one female. Both fertilizing rate and hatching rate were high, 84-87 percent and 39-66 percent, respectively, and almost same as those from artificial fertilization using eggs within one day after ovulation. These results thus demonstrated the usefulness of this low density culture for stable harvest of a number of fertilized eggs with good quality. The spawning of the barfin flounders was estimated to occur from 10 p.m. to 4 a.m. in the aquaria based on the serial observation of embryonic development in artificially fertilized eggs.