Ving Ching Chong

Relative importance of benthic microalgae, phytoplankton, and mangroves as sources of nutrition for penaeid prawns and other coastal invertebrates from Malaysia

Carbon, sulfur, and nitrogen stable isotope ratio techniques were used in 1989 and 1990 to evaluate the relative importance of algae and of mangrove detritus in the nutrition of two penaeid prawn species on the west coast of Peninsular Malaysia. Mangrove detritus was found to contribute to the nutrition of juvenile Penaeus merguiensis de Man living within tidal creeks, but not to adult P. merguiensis and juvenile and adult Parapenaeopsis sculptilis (Heller) captured offshore. Results from radiotracer feeding studies, with refractory 14C mangrove lignocellulose as the food source, indicated that juvenile P. merguiensis from tidal creeks assimilated mangrove carbon with an efficiency of 13.4%. This did not differ significantly (P=0.05) from the assimilation efficiencies of juvenile and adult P. sculptilis living offshore (10.0 and 10.9%, respectively); these values were significantly higher (P<0.001) than for adult P. merguiensis (2.1%). Thus, the differential contribution of mangrove material to the nutrition of prawns in the tidal creeks and offshore was not related to differences in the prawns ability to utilize detritus. Instead, our analysis of C stable isotopes in sediments indicated that mangrove detritus was generally more abundant within the tidal creeks than offshore. Juvenile prawns in the tidal creeks may also utilize mangrove material indirectly by feeding on small detritivorous invertebrates. Stable isotope analyses suggest that benthic microalgae constitute the other major dietary component for prawns living in tidal creeks. Prawns offshore were utilizing mainly phytoplankton-based material.

The fish and prawn communities of a Malaysian coastal mangrove system, with comparisons to adjacent mud flats and inshore waters

The fish and prawn communities of four coastal habitats in Selangor, Malaysia: (1) coastal mangrove swamps; (2) mud flats, including subtidal regions; (3) near inshore waters; and (4) far inshore waters, were examined with respect to species composition, abundance, diversity, similarity and sexual maturity. The number of fish species sampled for these habitats were 119, 70, 58 and 92 species respectively. For prawns, the number of species were 9, 16, 8 and 14 respectively. The mangrove community comprised 63–99% and 100% juvenile fish and prawn respectively. Despite a high species richness, it was low in fish species diversity due to the dominance (70%) of six species of fish of low economic value. In contrast, the prawn community was poor in species, and was dominated by threePenaeus spp. of high economic value. The intertidal mudflat community is largely transient and comprised mainly of species from both the mangrove and subtidal habitats. Fifty-six per cent of the fish population and 62·6% of the prawn population were juveniles. Many of the inshore fish and prawn species were also common species found in mangrove and mudflat habitats. Similarity coefficients indicate that the inshore fish and prawn communities are more similar to those of mud flats than mangroves. However, maturity studies indicate that only five species of fish are true migrants, that the majority of the fish species (juveniles and adults) are ubiquitous with a distribution that extends several nautical miles offshore. Results of this study indicate that tropical coastal mangroves function more importantly as feeding grounds than as nursery grounds for juveniles of commercially important fish species. Mangroves and mud flats are utilized during flood tides by many periodic foragers from the inshore waters. However, this study confirms that coastal mangroves and mud flats are important nursery areas for commercially important prawn species.

Mangroves as a habitat for fish and prawns

Mangrove inlets and creeks in Selangor, Malaysia are the habitat for 119 species of fish and 9 species of prawns. The majority of fish and all prawns sampled in the inlets were juveniles. The common fish species in the inlets in terms of weight were Arius sagor, Ambassis gymnocephalus, Liza subviridis, Toxotes jaculator, Sphyraena barracuda and Lates calcarifer. Prawns were represented by juvenile Penaeus penicillatus, P. merguiensis, P. indicus, Metapenaeus brevicornis and M. affinis. Samples from enclosure traps set on mudflats during ebbing water captured 37 species of fish and 11 species of prawns. The role of mangroves as nursery and feeding grounds for fish and prawns is reviewed in the light of recent work in Selangor. It is apparent that mangroves support fisheries by providing habitat and food.

The influence of fish cage aquaculture on pelagic carbon flow and water chemistry in tidally dominated mangrove estuaries of peninsular Malaysia

The impact of floating net cages culturing the seabass, Lates calcarifer, on planktonic processes and water chemistry in two heavily used mangrove estuaries in Malaysia was examined. Concentrations of dissolved inorganic and particulate nutrients were usually greater in cage vs. adjacent (approximately 100 m) non-cage waters, although most variability in water-column chemistry related to water depth and tides. There were few consistent differences in plankton abundance, production or respiration between cage and non-cage sites. Rates of primary production were low compared with rates of pelagic mineralization reflecting high suspended loads coupled with large inputs of organic matter from mangrove forests, fishing villages, fish cages, pig farms and other industries within the catchment. Our preliminary sampling did not reveal any large-scale eutrophication due to the cages. A crude estimate of the contribution of fish cage inputs to the estuaries shows that fish cages contribute only approximately 2% of C but greater percentages of N (32-36%) and P (83-99%) to these waters relative to phytoplankton and mangrove inputs. Isolating and detecting impacts of cage culture in such heavily used waterways--a situation typical of most mangrove estuaries in Southeast Asia--are constrained by a background of large, highly variable fluxes of organic material derived from extensive mangrove forests and other human activities.

Diversity, extinction risk and conservation of Malaysian fishes

A total of 1951 species of freshwater and marine fishes belonging to 704 genera and 186 families are recorded in Malaysia. Almost half (48%) are currently threatened to some degree, while nearly one third (27%) mostly from the marine and coral habitats require urgent scientific studies to evaluate their status. Freshwater habitats encompass the highest percentage of threatened fish species (87%) followed by estuarine habitats (66%). Of the 32 species of highly threatened (HT) species, 16 are freshwater and 16 are largely marine-euryhaline species. Fish extinctions in Malaysia are confined to two freshwater species, but both freshwater and marine species are being increasingly threatened by largely habitat loss or modification (76%), overfishing (27%) and by-catch (23%). The most important threat to freshwater fishes is habitat modification and overfishing, while 35 species are threatened due to their endemism. Brackish-water, euryhaline and marine fishes are threatened mainly by overfishing, by-catch and habitat modification. Sedimentation (pollution) additionally threatens coral-reef fishes. The study provides recommendations to governments, fish managers, scientists and stakeholders to address the increasing and unabated extinction risks faced by the Malaysian fish fauna.

The Role of Mangroves in Retaining Penaeid Prawn Larvae in Klang Strait, Malaysia

The mangrove-fringed Klang Strait, Malaysia, retains approximately 65 billion penaeid prawn larvae annually prior to their settlement in coastal nursery grounds. This phenomenon appears to be due principally to tidal currents and lateral trapping in mangrove-fringed channels, the wind playing an insignificant role.

Growth and production of biomass of Rhodovulum sulfidophilum in sardine processing wastewater

Aims: Rhodovulum sulfidophilum was grown in sardine processing wastewater to assess growth characteristics for the production of bacterial biomass with simultaneous reduction of chemical oxygen demand.

Detection of multiple potentially pathogenic bacteria in Matang mangrove estuaries, Malaysia

The deltaic estuarine system of the Matang Mangrove Forest Reserve of Malaysia is a site where several human settlements and brackish water aquaculture have been established. Here, we evaluated the level of fecal indicator bacteria (FIB) and the presence of potentially pathogenic bacteria in the surface water and sediments. Higher levels of FIB were detected at downstream sampling sites from the fishing village, indicating it as a possible source of anthropogenic pollution to the estuary. Enterococci levels in the estuarine sediments were higher than in the surface water, while total coliforms and E. coli in the estuarine sediments were not detected in all samples. Also, various types of potentially pathogenic bacteria, including Klebsiella pneumoniae, Serratia marcescens and Enterobacter cloacae were isolated. The results indicate that the Matang estuarine system is contaminated with various types of potential human bacterial pathogens which might pose a health risk to the public.

Molecular and morphological analyses reveal phylogenetic relationships of stingrays focusing on the family Dasyatidae (Myliobatiformes).

Elucidating the phylogenetic relationships of the current but problematic Dasyatidae (Order Myliobatiformes) was the first priority of the current study. Here, we studied three molecular gene markers of 43 species (COI gene), 33 species (ND2 gene) and 34 species (RAG1 gene) of stingrays to draft out the phylogenetic tree of the order. Nine character states were identified and used to confirm the molecularly constructed phylogenetic trees. Eight or more clades (at different hierarchical level) were identified for COI, ND2 and RAG1 genes in the Myliobatiformes including four clades containing members of the present Dasyatidae, thus rendering the latter non-monophyletic. The uncorrected p-distance between these four ‘Dasytidae’ clades when compared to the distance between formally known families confirmed that these four clades should be elevated to four separate families. We suggest a revision of the present classification, retaining the Dasyatidae (Dasyatis and Taeniurops species) but adding three new families namely, Neotrygonidae (Neotrygon and Taeniura species), Himanturidae (Himantura species) and Pastinachidae (Pastinachus species). Our result indicated the need to further review the classification of Dasyatis microps. By resolving the non-monophyletic problem, the suite of nine character states enables the natural classification of the Myliobatiformes into at least thirteen families based on morphology.

Novel life‐history data for threatened seahorses provide insight into fishery effects

Life-history variables for three incidentally captured species of seahorse (Kelloggs seahorse Hippocampus kelloggi, the hedgehog seahorse Hippocampus spinosissimus and the three-spot seahorse Hippocampus trimaculatus) were established using specimens obtained from 33 fisheries landing sites in Peninsular Malaysia. When samples were pooled by species across the peninsula, sex ratios were not significantly different from unity, and height and mass relationships were significant for all species. For two of these species, height at physical maturity (HM ) was smaller than the height at which reproductive activity (HR ) commenced: H. spinosissimus (HM = 99·6 mm, HR = 123·2 mm) and H. trimaculatus (HM = 90·5 mm, HR = 121·8 mm). For H. kelloggi, HM could not be estimated as all individuals were physically mature, while HR = 167·4 mm. It appears that all three Hippocampus spp. were, on average, caught before reproducing; height at 50% capture (HC ) was ≥HM but ≤HR . The results from this study probe the effectiveness of assessment techniques for data-poor fisheries that rely heavily on estimates of length at maturity, especially if maturity is poorly defined. Findings also question the sustainability of H. trimaculatus catches in the south-west region of Peninsular Malaysia, where landed specimens had a notably smaller mean height (86·2 mm) and markedly skewed sex ratio (6% males) compared with samples from the south-east and north-west of the peninsula.