Improvement of spawning in Siganus rivulatus: the impact of different LHRHa doses, spawning methods and sex ratio on spawning performance and egg quality

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Induced spawning is used to solve failure of complete oocyte maturation and fish spawning in captivity. Hormonal inductions with luteinizing hormone releasing hormone analogue (LHRHa) were examined to induce synchronized ovulation and improve spawning of wild-caught rabbitfish, Siganus rivulatus. Three experiments were carried out to study their impact on egg quality. Experiment I: LHRHa intramuscular injections of 50 and 100 µg kg-1 were used for two different groups respectively with a third control group. Experiment II: LHRHa injection (100 µg kg-1) was used to study the impact of both spontaneous spawning and stripping methods. Experiment III: LHRHa injection (50 µg kg-1) was used to study the influence on sex ratios. Two successive injections (LHRHa) were used for females in all experiments while male fish received only one dose. In experiment I, the response to higher dose showed a significant increase (p < 0.01) in egg diameters, latency time, total number of spawning fertilized eggs and hatching rate. In experiment II & III, a significant improvement (p < 0.01) was observed in all egg quality parameters with both spontaneous spawning and sex ratio (2 male:1 female). LHRHa injection is an adjunct to improve spawning performance and Siganus rivulatus culture production.

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