Study on Carapace Width Growth Band Counts Relationship of Orange Mud Crab, Scylla olivacea (Herbst, 1796) from Terengganu Coastal Waters, Malaysia.

BACKGROUND: Orange mud crab Scylla olivacea is one of the most important fisheries resources. A new development in ageing technique of crustaceans has been introduced. The detection of growth band deposited in hard structure of gastric mill in the cardiac stomach are found retained after moulting process can be used as age indicator and growth estimation. OBJECTIVE: This study was carried out to determine the comparison between carapace width and growth band count of S. olivacea in Malaysia. MATERIALS AND METHODS: Samples were collected from Setiu Wetlands, Terengganu, Malaysia from February until August, 2016. Samples were categorized based on their morphological measurements. The mesocardiac and zygocardiac ossicles in the gastric mill of S. olivacea was dissected out and preserved in solutions and underwent a cross sectioning process. A total of 76 of wild S. olivacea ranging from 6.56 to 12.84 cm in carapace width were analysed. The growth band counts were examined for each individual and ranging from 1 to 3 band counts. RESULTS: A positive linear relation was observed between CW and GBC with r2 = 0.5178, p<0.01. Overall, there was a strong, positive correlation between CW and GBC. Increase in CW were correlated with increases in GBC respectively for this species. CONCLUSION: Therefore, 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.

Effect of Excoecaria agallocha on non-specific immune responses and disease resistance of Oreochromis niloticus against Streptococcus agalactiae.

The current study was designed to evaluate the effects of Excoecaria agallocha leaf extracts on immune mechanisms and resistance of tilapia, Oreochromis niloticus, after challenge with Streptococcus agalactiae. Fish were divided into 6 groups; groups 1-5 fed with E. agallocha leaf extracts at 10, 20, 30, 40 and 50mgkg-1 level, respectively. Group 6 were fed without extract addition and acted as control. E. agallocha extracts were administered as feed supplement in fish diet for 28days and the hematological, immunological, and growth performance studies were conducted. Fish were infected with S. agalactiae at a dose of 15×105CFUmL-1 and the total white blood cell (WBC), phagocytosis and respiratory burst activities of leukocytes, serum bactericidal activity, lysozyme, total protein, albumin, and globulin levels were monitored and mortalities recorded for 15days post infection. Results revealed that feeding O. niloticus with 50mgkg-1 of E. agallocha enhanced WBC, phagocytic, respiratory burst, serum bactericidal and lysozyme activities on day 28 pre-challenge and on 3rd, 6th, 9th, 12th and 15th day post-challenge as compared to control. Total protein and albumin were not enhanced by E. agallocha diet. E. agallocha increased the survival of fish after challenge with S. agalactiae. The highest mortality rate (97%) was observed in control fish and the lowest mortality (27%) was observed with group fed with 50mgkg-1 extract. The results indicate that dietary intake of E. agallocha methanolic leaf extract in O. niloticus enhances the non-specific immunity and disease resistance against S. agalactiae pathogen.

Biology and population dynamics of the goby Pseudapocryptes elongatus in the coastal mud flat areas of the Mekong Delta, Vietnam.

This study describe the reproductive biological characteristics and population parameters of the goby, Pseudapocryptes elongatus (Cuvier, 1816), in the coastal mud flat areas of the Mekong Delta, Vietnam. A total of 1058 specimens was collected from January 2004 to June 2005 and results showed that the breeding season occurred with two spawning peaks in July and October. Length at first maturity (L(m)) was 15.4 and 16.3 cm for females and males, respectively. The batch fecundity estimates ranged from 2,652 to 29,406 hydrated oocytes per ovary in the fish ranging from 12.8 to 22.4 cm TL. Length frequency data of the goby ranging from 9.0 to 24.0 cm TL were analyzed using the FiSAT II software. The von Bertalanffy growth parameters were determined as L8 = 25.9 cm, K = 0.66 year(-1) and t(o) = - 0.26 year(-1). The longevity (t(max)) of the goby was estimated to be 4.55 years. There were two recruitment peaks with very different magnitudes and the means of these two peaks were separated by an interval of 5 months. Length at first capture (L(c)) was 10.05 cm, the instantaneous fishing mortality rate (F = 1.38 year(-1)) and natural mortality rate (M = 1.46 year(-1)) accounted for 49 and 51% of the total mortality (Z = 2.84 year(-1)), respectively. Relative yield-per-recruit and biomass-per-recruit analyses gave E(max) = 0.65, E0.1 = 0.55 and E0.5 = 0.33. Results show that the fish stock is subjected to growth overexploitation.