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.
Betta nuluhon, new species, is described from a hill stream habitat in western Sabah. This species is allied to both B. chini and B. balunga, and differs from rest of its congeners in the B. akarensis group in having the following combination of characters: yellow iris when live; mature males with greenish-blue iridescence on opercle when live; mature fish with distinct transverse bars on caudal fin; slender body (body depth 22.1-25.2 % SL); belly area with faint reticulate pattern (scales posteriorly rimmed with black); absence of tiny black spots on anal fin; lateral scales 29-31 (mode 30); predorsal scales 20-21 (mode 20). Notes on a fresh series of B. chini are also provided.
This study investigates the published literature and incorporates our field data from 1997 to September 2018 to generate an inventory report of primary freshwater fishes for Perak State in Malaysia. We critically examined and enumerated 186 species from 2 classes, 16 orders, 43 families and 114 genera in 57 localities. A total of 173 fish species (91.4%) are native to Perak and 17 species (8.6%) are non-native. The provisional checklist presented herein is conservative and excludes doubtful inventory records that lack synthesis and traceability. We encountered seven taxonomic discrepancies and we also could not confidently identify eight species. These are explicitly discussed to inform future workers.
Biodiversity surveys are crucial for monitoring the status of threatened aquatic ecosystems, such as tropical estuaries and mangroves. Conventional monitoring methods are intrusive, time-consuming, substantially expensive, and often provide only rough estimates in complex habitats. An advanced monitoring approach, environmental DNA (eDNA) metabarcoding, is promising, although only few applications in tropical mangrove estuaries have been reported. In this study, we explore the advantages and limitations of an eDNA metabarcoding survey on the fish community of the Merbok Estuary (Peninsular Malaysia). COI and 12S eDNA metabarcoding assays collectively detected 178 species from 127 genera, 68 families, and 25 orders. Using this approach, significantly more species have been detected in the Merbok Estuary over the past decade (2010-2019) than in conventional surveys, including several species of conservation importance. However, we highlight three limitations: (1) in the absence of a comprehensive reference database the identities of several species are unresolved; (2) some of the previously documented specimen-based diversity was not captured by the current method, perhaps as a consequence of PCR primer specificity, and (3) the detection of non-resident species-stenohaline freshwater taxa (e.g., cyprinids, channids, osphronemids) and marine coral reef taxa (e.g., holocentrids, some syngnathids and sharks), not known to frequent estuaries, leading to the supposition that their DNA have drifted into the estuary through water movements. The community analysis revealed that fish diversity along the Merbok Estuary is not homogenous, with the upstream more diverse than further downstream. This could be due to the different landscapes or degree of anthropogenic influences along the estuary. In summary, we demonstrated the practicality of eDNA metabarcoding in assessing fish community and structure within a complex and rich tropical environment within a short sampling period. However, some limitations need to be considered and addressed to fully exploit the efficacy of this approach.
Mesohabitat selection in fluvial fishes was studied in a small tropical stream of the Malay Peninsula. A total of 681 individuals representing 24 species were sampled at 45 stations within heterogeneous stream (ca. 1 km in length), in which water depth, water velocity, substrate size, and riparian canopy cover were measured as environmental variables. A canonical correspondence analysis (CCA) yielded a diagram that shows a specific mesohabitat selection of the fish assemblage, in which the species were plotted widely on the CCA1-CCA2 biplot. Generalized linear model also revealed a significant pattern of the mesohabitat selection of several species. Water velocity and substrate size mainly separated on CCA1, indicating variation of pool (deep, slow-flow section) and riffle (shallow, fast-flow section) structures is a primary factor of mesohabitat selection in the fluvial fish assemblage. The mean body weight of species significantly correlated with CCA1; larger species tended to inhabit pools, while small ones occupied riffles. The riparian canopy cover separated on CCA2. The trophic level of species significantly correlated with CCA2; herbivorous species (low trophic level) selected open sites without riparian cover, whereas omnivorous/carnivorous (middle-high trophic level) species preferred highly covered sites. In conclusion, our results suggest that mesohabitat selection is closely related to the species feeding habit, which is consistent with the results of previous studies.
The genetic population structure of red snapper Lutjanus malabaricus and orange-spotted grouper Epinephelus coiodes in Brunei and Sabah was investigated using allozyme electrophoresis. Samples were collected from three sites in Brunei for E. coiodes and from three sites in Brunei and Sabah for L. malabaricus. A total of 22 loci and 16 loci were scored, respectively. The index of fixation (F(ST) ) for the E. coiodes population was 0.176 but, in general, it lacked within-population structuring. The F(ST) was particularly high between Brunei Bay/Jerudong and Brunei Bay/ Kuala Belait, suggesting genetic subdivision on a small spatial scale. Isolation of Brunei Bay from the South China Sea may constrain the movement of adult fishes and larval dispersal, thereby reducing homogeneity among subpopulations. All variable loci for E. coiodes were in Hardy-Weinberg equilibrium except for MDH* and GTDHP* (P < 0.01), in which two subpopulations showed an excess of heterozygotes (P < 0.01). The study on the L. malabaricus population showed a heterozygote deficit of approximately 60% in variable loci (F(ST) genetic variation within population = 0.45; P < 0.05); however, the mean observed heterozygosity for the population far exceeded L. malabaricus populations in Australia and Indonesia. A F(ST) value of 0.076 revealed moderate genetic differentiation among subpopulations of L. malabaricus. The genotypes were likely to be drawn from the same distribution in Jerudong and Kuala Belait. This study infers that sustainable management of snapper and grouper resources in Brunei waters must take into account the presence of a single stock and two stocks, respectively.
In the crystal structure of the title compound, C(12)H(10)N(4), the pyridine ring makes a dihedral angle of 1.12 (9) degrees with the mean plane of the complete almost planar and crystallographically centrosymmetric molecule. There are stacks of parallel molecules along the a-axis direction, with alternate stacks having a herring-bone arrangement relative to each other and an interplanar spacing of 3.551 A.
Laboratory radiotracer experiment was performed to study the bioaccumulation of 109Cd and 134Cs in the Malaysian common fish White seabass (Lates calcarifer). The aim of this study was to compare the biokinetics of uptake these two contrasting radionuclides by White seabass in laboratory condition scale. Experiments were designed to determine the processes controlling uptake of both radionuclides following exposure via seawater. In this study, the curve shapes of the uptake kinetic of 109Cd and 134Cs in White seabass were slightly linear and gradually increased with increasing of exposure time but were not reach equilibrium in the period of the study of 21 days. This phenomenon can be concluded that radioelement concentrations of 109Cd and 134Cs; and exposure duration of this experiment may not adequately to reach steady-state condition for uptake kinetic of those radioelements in White seabass. Furthermore, this was indicated that the uptake rate of 109Cd was 1.79 times faster than 134Cs due to some factors may probably influenced the output of this experiment such as different element accumulation strategies, physiological, behavior of radioelements, etc.
The behaviour and aggregation of fish in an artificial reef area in Tioman Island, Malaysia, was observed using underwater videography under a combination of shooting conditions. The camera distance and direction relative to the neighboring artificial reef module was varied, and comparisons of images with a color filter were made. A distance of 260 cm at a diagonal shooting angle provided a suitable observation of the reef fish around the reef module, and a red color filter provided a truer color replication in morning observations while better images were obtained without the color filter in afternoon light environments. Four criteria were considered to assess the artificial reef effectiveness: total abundance, appearance rate, residence time and feeding frequency. A total of 824 individuals were observed during the study. Mean residence times were shorter for schooling fishes such as Caesio caerulaurea and Liza subviridis, and longer for solitary swimmers like Cephalopholis boenak and Scolopsis bilineatus. Feeding frequency was lower for schooling fishes. A significant correlation was obtained between the feeding frequency and residence time for the high feeding frequency fishes (r = 0.89; p<0.05). The effectiveness of the artificial reef was suggested to be significant in solitary swimmers but less so for schooling fishes.
Neenchelys buitendijki Weber and de Beaufort, 1916 from Malaysia is reported for the first time. Five specimens collected
from Matang, Peninsular Malaysia, represent the third record in the Indo-western Pacific region. A detailed description
is provided to document the species into the fish fauna of Malaysia.
Fish is one of the major sources of protein among Malaysians. This has made incidents of fish bones lodged in the throat fairly common clinical problems. Plain radiograph, which is the first line of imaging in such cases, has been reported to have low sensitivity. Besides the location, the degree of radio-opacity of the bone is another important factor and is species dependent. This study was undertaken to determine the radio-opacity of bones from commonly consumed fish in Malaysia. A total of 15 types of fish were identified, six of them were opaque even when embedded and three were visualized in the simulated airway. In terms of radio-opacity, the commonly consumed fish in Malaysia possessed opaque bones and this fact can help doctors identify the location of the foreign body in the throat.
For over 150 years, ecologists have been striving to explain fundamental patterns of biological diversity, such as the observation that communities invariably consist of common and rare species, and to unravel the processes that underpin these patterns. This task is increasingly urgent given the accelerating loss of biological diversity. Although fishes are the most diverse vertebrate taxon and fish communities occur in a wide range of habitats, they have been relatively little studied in the quest to elucidate the processes that shape patterns of biological diversity. Here, some of the topics that investigations of fish assemblages can illuminate are highlighted. These include the characteristics of ecological communities and the role that dispersal limitation plays in structuring them, the distinction between core and occasional species, the insights that evaluating abundance in different currencies can bring and the assessment of community capacity. Questions are identified that future investigations of fish communities might tackle and a case study of a biodiverse ecoregion (Thailand and Peninsula Malaysia) is used to illustrate the need for better links between these ecological questions and effective conservation practice.
Community resistance to, and resilience from, perturbation will determine the trajectory of recovery from disturbance. Although selective timber extraction is considered a severe disturbance, fish communities from headwater streams around Danum Valley Field Centre, Sabah, Malaysia, showed few long-term changes in species composition or abundance. However, some species showed short-term (< 18 months) absence or decrease in abundance. These observations suggested that both resistance and resilience were important in maintaining long-term fish community structure. Resistance to perturbation was tested by monitoring fish communities before and after the creation of log-debris dams, while resilience was investigated by following the time-course of recolonization following complete removal of all fish. High community resistance was generally shown although the response was site-specific, dependent on the composition of the starting community, the size of the stream and physical habitat changes. High resilience was demonstrated in all recolonization experiments with strong correlations between pre- and post-defaunation communities, although there was a significant difference between pool and riffle habitats in the time-course of recovery. These differences can be explained by the movement characteristics of the species found in the different habitats. Resilience appeared to be a more predictable characteristic of the community than resistance and the implications of this for ensuring the long-term persistence of fish in the area are discussed.
Haruan, Channa striatus, is a snakehead fish consumed in many parts of the southeast Asian region. It is believed to promote wound healing, as well as reduce post-operative pain. In an attempt to establish the scientific basis for the alleged pain-relieving benefits of this fish, we studied the antinociceptive effects of whole fillet and mucus extracts from haruan in the mouse using the abdominal constriction and tail flick tests. In the abdominal constriction test, the 30 min fillet extract exhibited concentration-dependent inhibition of the writhing response in the 10-50% concentration range, with 20% as the IC50 value. This activity was not dependent on the duration of extraction, with no significant differences among the extracts obtained at durations of 10, 20, 30, 60, 90 and 120 min (range between 45-54% inhibition at 20% concentration). The mucus extract also showed concentration-dependent inhibition of the abdominal constriction response-at the highest concentration used the average inhibition was 68.9%, while IC50 value was 25%. Neither the fillet extract (30 min, 20%) nor the mucus extract (25%) had any demonstrable effect on the tail flick latency on their own, but significantly enhanced the antinociceptive activity of morphine in this assay. Similarly, low concentrations of the mucus and fillet extract enhanced the effects of morphine in the abdominal constriction test. Collectively, these results suggest a scientific basis for the folklore practice of eating haruan fish in the post-operative period for pain relief: Haruan extracts have antinociceptive activity and enhance the activity of other antinociceptive agents.