An ecological approach: a viable option for aquaculture industry in Malaysia

Aquaculture sector in Malaysia is poised to playa major role to compensate for the declining capture fisheries, and is expected to emerge as one of the major agricultural contributors to the national economy. The industry is anticipated to increase the production to 600,000 mt, generating returns up to US$2.63 billion by 2010. This is a significant increase of approximately 360 at US$255.34 million. Aquaculture involves utilization of natural resources such as clean water, vast tracks of land, feed materials and fertilizers to produce desirable products with simultaneous production of organic and chemical wastes. Thus, the successful development of this sector is dependent on the nation's ability to utilize its resources efficiently and sustain its growth without adversely affecting the aquatic environment. At present, most aquaculture practices in Malaysia generate adverse impacts on aquatic environment, the very resource that determine the sUccess and the sustainability of the aquaculture industry. Wetland habitats such as mangroves, estuaries, sea-grass beds, coral reefs and mudflats are particularly vulnerable, especially when the impacts exceeded the ecosystem's resilience and carrying capacity. However, carrying capacity in various ecosystems is poorly known and thus the tendency to exceed the upper limit seems to be common in most environments. Adverse impacts associated with aquaculture, especially the intensive systems, include habitat destruction, discharge of effluents with high organic contents, contamination of the aquatic environment with chemicals, eutrophication, disease outbreak, effects of escaped- exotic species and decrease in biodiversity

Heavy metals in neuston from the straits of Malacca.

Heavy metals cadmium, lead, copper and zinc in neuston were analyzed from samples collected with a modified neuston net (310 μm mesh size) during an oceanographic cruise from July 29 to August 8, 2000 in the Straits of Malacca. The period of sampling coincided with South-West (SW) monsoon. The heavy metal concentrations in neuston were relatively low: ranging from 1.19-1013.70 μg g-1 wet weight for copper, 16.54-235.78 μg g-1 wet weight for zinc, 3.92-36.08 μg g-1 wet weight for lead and from 0.32-4.09 μg g-1 wet weight for cadmium. The heavy metal concentrations in neuston in this study were within the ranges published elsewhere, except for cadmium, there were significant differences (p <0.05) in concentrations of Cu, Pb and Zn between northern, central and southern parts of the Straits. However, concentrations of Cu and Zn were significantly (p 0.05). The presence of two groups of stations with high and low heavy metal concentration as revealed by multivariate analyses corresponded mostly to near-coastal and neritic waters, respectively

Siltation in Zoo Negara Lake

In a study of Zoo Negara Lake, it was found that the turbidity and total residues were higher in the lake than in the upstream station where there is no effect of soil erosion. The immediate results of massive flows of erosion silt were the change of water colour and reduction in the depth of the lake. Effects of siltation such as the reduction in light penetration and aquatic organisms are discussed

The effects of phosphorus and nitrogen on phytoplankton dominance in tropical fish ponds

Nine ponds were used to determine the effects of phosphorus (P) and nitrogen (N) loading on: the phytoplankton dominance in tropical fish ponds. Three ponds received triple superphosphate (TSP), three received triple superphosphate plus urea (TSPUrea) and the rest served as the control. Addition of both phosphorus and nitrogen (TSP-Urea treatment) resulted in higher total phytoplankton than the TSP treatment and the control (P < 0.05). In general, blue-green algae formed the dominant group in TSPUrea treatment ponds followed by dinoflagellates, green algae, euglenoids and diatoms. In TSP-Urea treatment ponds, green algae was the most abundant group followed by blue-green, dinoflagellates, euglenoids and diatoms. Addition of combined nitrogen and phosphorus to the ponds not only significantly increased (P <0.05) total phytoplankton densities, but also caused a shift from bluegreen algal dominance to green algae. TSP treatment ponds showed significantly higher: blue-green algae than TSP-Urea treatment in the early culture cycle. However, as the ponds became more productive with time, blue-green algae also appeared to be common in TgP-Urea treatment in spite of high N: P ratios. The blue-green algae increased linearly with the increase of total phytoplankton in all treatments (r2 = 0.58. P < 0.01)

Status, prospects and potentials of echinoid sea urchins in Malaysia

Among the bottom-dwelling invertebrates, sea urchins have been considered as the high-valued new marine bioresource in Asia. They inhabit the depths of coral reefs and rocky shores that are covered with coralline algae and seaweeds. They are usually spherical in shape, and their whole body is covered by numerous thorns or spines that act as defense mechanism against predators. The sea urchin gonad has been used as luxury food and folk medicine by the peoples of certain countries. For this reason, sea urchin became an important product and fetches high price in international markets. It also plays an important role towards providing employment opportunity and income source to the coastal communities in many Pacific island countries including Malaysia. Sea urchin gonad is very rich in essential proteins, lipids and bioactive compounds having profound nutraceutical and pharmaceutical importance. Nowadays, sea urchins have been harvested for trade with Asia and are perhaps one of the worthy exports from the Indo-Pacific islands. Unluckily, owing to increasing demand and prices, combined with the development of cash economies and growing coastal populations, it has led to extensive overfishing of the resource across much of this region, especially in Pulau Bum Bum near Semporna between Philippines and Eastern Malaysia. Nevertheless, some Pacific island countries have completed research trials on breeding, nursing and culture techniques, but such types of research works are yet to be completely explored and determined in Malaysia. In the recent years, undiscriminating catching and over-exploitation of sea urchin turns out to be excessive and disrupts its sustainability. Because of this prevalent situation, aquaculture of sea urchins through the appropriate breeding, seed production and culture techniques in captivity should be the best alternative to solve these problems in a worthwhile and sustainable manner

Status of planktonic copepod diversity in the Merambong seagrass meadow, Johor, Peninsular Malaysia

The diversity and abundance of planktonic copepods were analysed from zooplankton samples collected within six times throughout the year in the Merambong seagrass area. A total of 48 species from 20 genera and 15 families comprising an average of 78.8%, of the total zooplankton populations were recorded throughout the sampling period. Among the copepod groups, calanoids were the most abundant inhabiting all the stations, taking an average of 51.2% of the total copepod populations. The most common species observed in the area were Paracalanus parvus, Paracalanus elegans, Oithona rigida, and Euterpina acutifrons. The highest copepod density was recorded at 17.0±2.8 x104 individuals/m3. Copepod species diversity (H’) and species richness (d) were highest at H’ = 3.58 and d=7.08, respectively. Species evenness (J) was, however, relatively constant (0.9) during the entire sampling period. The findings from this study provide important baseline information for future research and monitoring programs

Population Growth and Production of Apocyclops dengizicus (Copepoda: Cyclopoida) Fed on Different Diets

This study was carried out to investigate the effects of various diets: 4 monoalgal diets: Nannochloropsis oculata (N), Isochrysis galbana (I), Chaetoceros calcitrans (C), and Tetraselmis tetrathele (T); 4 mixed algal diets: N+I+C+T(NICT), N+I+C(NIC), C+T(CT), and I+T(IT); and 2 nonalgal diets: baker’s yeast (BY) and prepared shrimp feed (SF) on population growth and density of Apocyclops dengizicus. The type and density of diet had significant effects on the growth and density of A. dengizicus (P , 0.01). Of tested diets, T and CT were optimum diets due to higher density and growth rate of A. dengizicus compared to other diets. Their high dietary value was related to the higher contents of polyunsaturated fatty acid, particularly docosahexaenoic acid (22:6n-3), eicosapentaenoic acid (20:5n-3), and arachidonic acid (20:4n-6) compared to A. dengizicus cultured on other diets. The results of the present study illustrated that T. tetrathele was the most suitable food for the culture of A. dengizicus

Vertical distribution of zooplankton and copepod community structure in the Straits of Malacca.

Vertical distribution of zooplankton biomass and abundance, copepod taxonomic composition and species diversity were analyzed at eight stations during an oceanographic expedition along the Straits of Malacca. Samples were collected in vertical hauls (140 μm mesh using 45 cm diameter NORPAC net) from four depth strata. Zooplankton biomass was higher at 10-20 m depth in the central and southern parts of the Straits compared to the other depth layers, but the differences were significant (p<0.05) only in the southern part. A total of 96 species of planktonic copepods belonging to 35 genera were identified in the surveyed area. Except for the 10-20 m depth layer in the northern part of the Straits, copepods were the major fraction of the total zooplankton at all depths. In the northern and central parts of the Straits, the deeper layers had higher species diversity indices than in the surface waters, mainly due to higher evenness in the deeper layers. The lower species diversity in the deeper layers of the southern region was attributed to the dominance of a few species

Effects of delayed metamorphosis on larval survival, metamorphosis, and juvenile performance of four closely related species of tropical sea urchins (genus Echinometra)

We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22–24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis

Mercury in zooplankton from the Malacca Straits.

Total mercury concentration in mixed zooplankton was determined from near surface waters in Malacca Straits (05o 59' N, 99o 59' E and 01o 10' N, 103° 29' E). Total mercury concentrations in mixed zooplankton ranged from 1.12 to 4.68 ng dry weight g-1 with a mean of 2.08 ± 0.25 ng dry weight g-1 and showed a decreasing trend from nearshore to offshore areas. Higher mercury concentrations were found in nearshore waters (mean of 2.79 ± 0.49 ng dry weight g-1). Total mercury content was higher in the southern part of the Straits compared to the other parts. The zooplankton in the Malacca Straits environment is not heavily contaminated with mercury