The behavioral and physiological study on lunar-related maturation and spawning in honeycomb grouper.

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Honeycomb grouper, which is distributed in the sub-tropical and tropical area in Pacific Ocean, is known as a lunar-related spawner. However, details of gonadal development and spawning in this species are not well understood. In this study, we investigated the gonadal development and hormonal changes in female collected from the fringing reef area around Sesoko Island during spawning season and observed the spawning in artificial conditions. Moreover, we investigated the spawning migration to the outside of fringing reef for spawning using biotelemetry method.Gonadosomatic index increased rapidly and reached the maximum level around the full moon in late May or early June, when ovaries were occupied with oocytes of the tertiary yolk stage. The fish of maturational size disappeared from the fringing reefs for a few days after the full moon. When the fish appeared again in the same reef area, there was no vitellogenic oocyte in the ovary. These results indicate that the fish spawned in the area outside the fringing reefs after the full moon. In artificial conditions, the final oocyte maturation and spawning were observed for a few days after the full moon, while the maturated fish migrated outside the fringing reefs in natural conditions. The spawning of individuals was carried out for three or four days. This results elucidated clearly that honeycomb grouper is a lunar-related spawner.