The Effect of Age/Size on Plasma Sex Steroids and Aromatase activity of Asian Seabass (Lates calcarifer) when transferred to ideal hatchery conditions

Asian Seabass, Lates calcarifer precocious sex change is problematic for efficient hatchery operation. Seabass grown in freshwater farms were transfer to brackish water (32 g/L) at 28 °C and fed to satiety until acclimated. Blood, brain and gonad were collected and analysed. Brain aromatase activity appeared to respond to age/size rather than environmental conditions while gonadal aromatase was detectable only in the 700 – 1000 g, Plasma T was increased in response to the environmental change in fish groups of 300500 g and 700-1000 g while the 50-100 g and 2.5-4 kg had no significant increase while Plasma E2 increased significantly in all groups of fish and 11-KT was detected in the 700 1000 g and 2.5 4 kg fish having no significant difference. Data indicate that the hormonal conditions are pre-requisite for inducing sex change in L. calcarifer are present in this species from 435 ± 27 g.