Effect of Water Salinity on the External Morphology of Ovarian Maturation Stages of Orange Mud Crab, Scylla olivacea (Herbst, 1796) in Captivity

BACKGROUND AND OBJECTIVE: Mud crab from the genus Scylla are considered as one of the most demanded seafood items nowadays as their flesh has high quality, tasty and higher growth rate thus support and boosted expansion in aquaculture sector especially in Malaysia. Present study was designed to focus on the effect of water salinity on the ovarian maturation of orange mud crab, Scylla olivacea based on morphological characteristics.

METHODOLOGY: Samples were collected from Setiu wetlands, Terengganu, Malaysia from July-September, 2015. Ovarian maturation of S. olivacea was classified into four stages based on previous study which were: Immature (Stage 1), early mature (Stage 2), late mature (Stage 3) and fully mature (Stage 4).

RESULTS: Morphologically as the ovary develop the colouration start to change from translucent or whitish in colour and sometimes creamy to pale yellow, follow by light orange and lastly reddish orange. Stage 1 ovary was translucent and whitish in colour, stage 2 ovary was pale yellow in colour, stage 3 was light orange and stage 4 ovary was reddish orange in colour. Gonad Somatic Index (GSI) of S. olivacea remained low at stage 1 and 2 and began to increase started at stage 3. This present study involved three different salinities treatments, which treatment 1 (10 ppt), treatment 2 (20 ppt) and treatment 3 (30 ppt). Treatment 2 produce the highest number of stage 4 ovarian maturation based on colouration and the highest GSI recorded, follow by treatment 1 and lastly treatment 3.

CONCLUSION: This present study proved that salinity does affected the ovarian maturation of S. olivacea in captivity and provides important information regarding the effect of water salinity on ovarian maturation for further studies on reproductive biology of this species.