Effects of exogenous hormones and broodstock age on the spawning response of captive silver therapon Leiopotherapon plumbeus

Abstract

Evaluation of appropriate hormone and ideal broodstock age for optimal breeding efficiency may ensure the production of good quality eggs and larvae in the hatchery. In this study, the spawning response of captive silver therapon <i>Leiopotherapon plumbeus</i> to various hormonal treatments and broodstock age was examined. In Experiment 1, spawning success, latency period, absolute and relative fecundity, fertilization and hatching rates, and larval production of female silver therapon broodstock were determined after ovulation and spawning in response to human chorionic gonadotropin (hCG; 5000 and 10,000 IU/kg), Ovaprim (0.5 ml/kg), hCG + Ovaprim (5000 IU + 0.5 ml/kg; 10,000 IU + 0.5 ml/kg) or hCG + domperidone (5000 IU + 0.5 ml/kg; 10,000 IU + 0.5 ml/kg). In Experiment 2, reproductive performance of four domesticated broodstock age groups (1⁺, 2⁺, 3⁺ and 4⁺-year old) was examined for five consecutive months, coinciding with the spawning season. Higher dose of hCG + Ovaprim resulted in higher spawning (100%), fertilization (99.7 ± 0.1%), and hatching (85.8 ± 5.5%) rates than the other treatments. The effect of age on reproductive indices was not significant. However, better spawning performance was observed in 1⁺ to 3⁺-year old broodstock, with higher fertilization (96.8–98.5%) and hatching (63.7%–77.2%) rates than among the oldest age group (82.9% and 57.2%). Together, results suggest that the combination of hCG + Ovaprim is highly effective in inducing ovulation and spawning in silver therapon, and that domesticated broodstock up to 4⁺ years of age could still be used for breeding activities and seed production.