Marudu Bay, north coast of Sabah is characterized with mesotrophic water body and typical environmental parameters
throughout the year. The current study was undertaken to evaluate the effect of environmental parameters and nutrients
in mesotrophic water on the occurrence and distribution of potentially harmful phytoplankton species. The samplings
were conducted over a period of thirteen months, covering southwest monsoon (SWM), inter-monsoon (IM), and northeast
monsoon (NEM), at ten stations throughout the bay. Physical parameters (temperature, salinity, pH, dissolved oxygen,
current speed and secchi depth), biological parameters (cell densities of phytoplankton) and chemical parameters
(phosphate, nitrate, silicate and ammonia) were examined. The results indicated at least eight potentially harmful
phytoplankton species (Dinophysis caudata, D. miles, Ceratium furca, C. fursus, Prorocentrum micans, P. sigmoides, P.
triestinum and Pseudo-nitzschia sp.) were detected in north coast of Sabah. However, the potentially harmful phytoplankton
species contributed only about 1.3% of the total phytoplankton community. Under nutrient deprivation conditions, the
potentially harmful phytoplankton species distribution was mainly influenced by the ability to utilize other nitrogen
sources, cell mobility and toleration to low nutrients environments.
Sabah has extensive mangrove forests surrounded by oceanic waters which provide suitable habitat for many species of animals including mud crabs (Scylla spp.). This study was conducted to obtain information on the species composition, distribution and catch per unit effort in Marudu Bay, Sabah. Samplings were done monthly in five mangrove areas along the river channels in Marudu Bay (06°33’N; 114°44’E) from October 2012 to September 2013 using collapsible baited crab traps. From a total of 1859 mud crab specimens caught in Marudu Bay, three species were identified. Scylla tranquebarica was the dominant species forming 78% of the total followed by S. paramamosain 13% and S. olivacea 8%. The number of males (n=1224) was higher compared to females (n=635) with an average sex ratio male : female of 1.0:0.5. The catch per unit effort (CPUE) showed an average value of 0.55 trap-1 day-1 and revealed a declining trend throughout the sampling. S. tranquebarica was widely distributed in all the rivers surveyed, however, it mostly occurred in near the lower reaches of the river near the areas open to the sea where average water salinity ranged from 12.98 to 14.28 ppt and the environment favoured the growth of Rhizophora sp. Other species, S. paramamosain and S. olivacea, were mostly found in upstream areas covered generally by Nypa sp. and where average water salinity varied from 6.93 to 7.50 ppt. The information on the species composition, distribution and CPUE of the mud crabs in Marudu Bay can be useful for mud crab fisheries resources management in Sabah.
The prevalence of antibiotic resistant bacteria in aquaculture has reached alarming proportions and intensified the search for microbe derived antimicrobial compounds. This study isolated bacteria from the intestine of Sagor catfish (Hexanematichthys sagor) and screened it for antagonistic properties. Five out of 334 bacterial isolates inhibited growth of fish pathogens. The 5 bacterial strains included relatives of Shewanella haliotis, Myroides odoratimimus, Vibrio harveyi, Vibrio alginolyticus and Alcaligenes faecalis. The growth profiles and probiotic properties of these bacteria were examined. The results showed that the isolate 9 (3) 7.5.2.1, whose closest relative was S. haliotis exhibited growth and probiotic advantage compared to the other bacterial strains, such as highest doubling time and the ability to survive at all experimental temperatures (18 to 60℃) , and bile concentrations (0.01 to 1.00%) and pH (pH2 to 9) . While the bacteria with probiotic properties were successfully isolated. Further study is necessary to examine the efficiency of the probiotic candidate bacteria in boosting fish immunity against pathogens.
Pathogenic marine fungi, Lagenidium thermophilum is known causative agent in the crustacean industry. Current disinfection practice in hatchery has risks and negative impacts which prompts suitable substitute to synthetic antifungal agents. Thus, this study was conducted to evaluate the antifungal potential of postbiotic from four potential probiotics towards marine oomycetes, L. thermophilum IPMB 1401. The screening test showed that the Lactobacillus plantarum GS12 and Bacillus cereus GS15 postbiotics were positive for antifungal activity on L. thermophilum IPMB 1401. These two bacterial extracts have minimum inhibitory concentration （MIC） at 50%. The toxicity assay on MIC level of the postbiotic revealed that the cumulative mortality of brine shrimp nauplii exposed to B. cereus postbiotic was significantly lower compared to L. plantarum GS12 postbiotic and formalin. This indicates a high potential of B. cereus GS15 as a prospect for alternative control method for fungal infections in the crustacean culture industry.