Ninety-seven individuals of Pacific saury Cololabis saira collected off Kumano in Mie Prefecture on February 6, 2008 were kept in a 30 m³ columnar tank at 15°C. They were reared under light levels adjusted to 1,400 lx between 08:00 to 17:00 and 20 lx between 17:00 to 08:00 using five halogen lamps. Ratio of the total number of eggs spawned between 08:00 to 13:00, 13:00 to 17:00 and 17:00 to 08:00 was 62%, 20% and 18% respectively from March 22 to April 20, 2008. Also as a result of counting spawning behavior per hour, spawning occurred actively between 08:00 to 13:00, while under 20 lx conditions 97% of spawning activity occurred between 06:00 to 08:00. This indicates that Pacific saury probably actively spawned from pre-dawn to noon.