Orange mud crab; (Scylla olivacea) has high commercial significance and is considered as one of the highly sought luxury seafood items. It is reported that the numerical knowledge derived from length or width and weight association accelerates the general information on welfare of individuals, biological, ecological factors, variation in growth according to sex, maturity, gonad development and breeding seasons of particular species1,2. But; few literature is available regarding growth and age assessment of Scylla olivacea in Malaysia3,4,5.
The growth band are deposited in a hard structure such as scales, bones, vertebrae and otolith in fishes and shells in bivalves6 and this can be used to determine the age of an animal7. Moreover; current investigation reported an enhanced attention in ageing evaluation and growth development on crustaceans by utilizing growth bands deposited on hard structures in gastric mill and eyestalk of the animals8,9,10,11. In addition; Campana12 suggested that in otolith of fishes; growth band deposition seems to be the most trustworthy to calculate age in them.
Because of few research published on development and age determination; N. Hasyima Ismail and colleagues designed an experiment to assess the Carapace Width (CW), Growth Band Counts (GBC) relationship of S. olivacea collected from Setiu Wetlands, Terengganu, Malaysia and to identify the ageing and growth development of this mud crab species.
For this experiment; scientists obtained aamples in 2016 from Setiu Wetlands, Terengganu, Malaysia (February to August). Samples were categorized based on their morphological dimensions. Researchers dissected the mesocardiac and zygocardiac ossicles in the gastric mill of S. olivacea and preserved these samples in solutions. Afterwards; cross sectioning was done. A total of 76 of wild S. olivacea ranging from 6.56 to 12.84 cm in carapace width were analyzed. Moreover, the growth band counts were observed for each individual and ranging from 1 to 3 band counts.
Research team noted a positive linear relation between CW and GBC with r2 = 0.5178, p<0.01. On the whole, there was a strong, positive correlation between CW and GBC. Amplification in CW was correlated with enhancement in GBC respectively. Conclusively, the carapace width, growth band counts and body weight can be used to improve data on growth, recruitment, maturation and mortality. Thus, this study would able to improve new ageing technique and contribute greatly to improve the conservation and management of S. olivacea in Setiu Wetlands, Terengganu, Malaysia. This study can accelerate commercial importance of crabs as well as other species regarding aqua farming.
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18 August, 2019