Seasonal changes in three indices of gonadal maturation in male golden rabbitfish (Siganus guttatus): implications for artificial propagation

Monthly changes of hepatosomatic index (HSI), gonadosomatic index (GSI), and plasma testosterone (T) levels in the reproductive season of male golden rabbitfish ( Siganus guttatus ) in captivity were investigated by sampling the liver, testis, and blood. HSI and GSI were estimated as percentage of relative weight of liver and testis to total body weight, respectively. Plasma T levels were measured using enzyme immune assay (EIA). Fragments of the testis were embedded in paraffin, cut to 5 μm thickness, and stained with Harris’ hematoxylin and eosin. The results included seasonal changes in HSI, GSI, T, and testicular stages. The plasma T levels were observed high at spermation stage and during February–March and May–June. The values of HSI were monthly fluctuations, but no significant differences between testicular stages were observed. The GSI values continuously exhibited a significant increase from December to April and maintained at high levels until June. GSI continuously increased from stage II (immature testis) to stage V (spawning testis). There was correlation between GSI and testicular stages. Histological sections showed that male golden rabbitfish are multiple spawners and spawning season starts from March to June. These results contribute to further understanding of reproductive biology in golden rabbitfish, which can be implicated for artificial propagation.