Advanced Spawning in Yellowtail, <i>Seriola quinqueradiata</i>, by Manipulations of the Photoperiod and Water Temperature

Abstract

The present study was performed to examine the combined effects of photoperiod control, namely one-month short-day treatment followed by long-day treatment and water temperature control (≥19°C) on ovarian maturation and HCG-induced spawning in yellowtail. In experiments conduced in 1995 and 1996, the daylength was set to 8 hours (8L-16D) for one month followed by a 10 hour extension to 18 hours daylength (18L-6D) for the next month under controlled water temperature before injection of human chorionic gonadotropin (HCG). Female yellowtail broodstock kept under both conditions of controlled photoperiod and water temperature were induced to mature more rapidly than those kept under natural conditions. Neither controlled condition of photoperiod nor water temperature was sufficient to induce the maturation of yellowtail. In both years, only fish kept under both conditions controlled were able to spawn in advance of February. Consequently, manipulations of the photoperiod and water temperature are effective in accelerating the maturation of female yellowtail broodstock and for obtaining an early egg collection from yellowtail treated with HCG.