Daily Spawning Rhythm During Spring and Autumn Spawning Seasons in the Tobinumeri-Dragonet Repomucenus beniteguri.

Abstract

Tobinumeri-dragonet has two spawning seasons, spring and autumn, within a single year in Lake Hamana, but it is not clear whether the same individual spawns during both spawning seasons, or whether there are two different populations of tobinumeri-dragonet which spawn in spring and autumn, respectively. In the present study, the spawning rhythms of 12 females were individually monitored from April 20 to December 30, 1987 in tanks under natural conditions. Daily spawning was observed during the period from May to late July and from late August to the end of November. No spawning was observed during late July to late August and in December. Four females which were caught and reared in a stock tank until April matured and spawned daily in the spring spawning season. However, they all died during or after the spring spawning season. Two females caught in spring spawned daily in both the spring and autumn spawning seasons. The largest number of eggs spawned from one female was 32, 000/day, and the average number during both spawning seasons was 7, 200/day. One of the females repeated spawning 138 times during June 13 to November 26 except during late July to late August. The onset time of spawning ranged between 1600-2000h.