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The tire track eel, Mastacembelus favus, is an economically important freshwater fish in mainland Southeast Asia. Understanding the spatial population structure is important to design an effective and efficient management of the species. The aim of this study was to investigate the genetic diversity and structure of M. favus populations. In total, 519 individuals from 30 locations across its distribution range were genotyped using a set of eight polymorphic microsatellite loci. Results showed that populations in Mekong and Chao Phraya exhibited higher genetic variability than those from Gulf of Thailand and Malay–Thai Peninsula. Clustering results revealed two evolutionarily isolated groups geographically separated at Northeastern Cambodia; the more widespread group was further divided into two subclusters. The spatial genetic variation and structure of its populations are attributed to the evolutionary history and population dynamics of the species. The study provides important information for the management and conservation of M. favus in Southeast Asia.

The drastic changes in hydroelectric reservoir development created a completely new ecosystem that affects the river, particularly in the inundated area. In this study, five Neolissochilus soroides and Channa lucius were surgically implanted with a unique coded acoustic transmitter to observe the habitat utilisation and movement activity in Tembat Reservoir after the inundation process. All of the individuals were released into the transition zone of the reservoir and observed using passive and active acoustic tracking devices from April to December 2018. Kruskal-Walis test showed no significant difference between the average size of core area for N. soroides and C. lucius, x2(1) = 1.320, p = 0.251. The home range also showed a similar result for N. soroides and C. lucius where there was an insignificant difference, x2(1) = 0.273, p = 0.602. However, duration wise, N. soroides spend more time in the transition zone, R1 (M = 2.71 hrs, SE = 0.38), and C. lucius in the riverine zone, R5 (M = 7.14 hrs, SE = 6.13) and R6 (M = 3.85 hours, SE = 6.36). From the active tracking survey, PCA identified three (62.32%) and four (71.19%) components with eigenvalues greater than 1 for N. soroides and C. lucius, respectively. Three most important habitat parameters for N. soroides were the size of river (r = 0.97), existence of canopy cover (r = 0.77), and substrate type (r = 0.79).While, for C. lucius were mesohabitat type (r = 0.79), distance to riffle (r = 0.97), existence of canopy cover (r = 0.90), and elevation (r = 0.90). A 24-hour movement frequency analysis for both species revealed two active hours of movement at dusk and dawn for both species. From the study, it is known that N. soroides and C. lucius respond differently towards the inundation of the reservoir. The findings in this study can be implemented for effective aquatic management and conservation plan to ensure sustainable dam development.

In this paper, we studied some biological aspects of big eye scad (Selar crumenophthalmus) from Maldives. The fish sample was collected from the local fish market at Bangaa Faru, Male, Maldives. The length of the samples were ranged from 7.7 cm to 24.5 cm (mean value = 16.85 ± 2.82 cm) in fork length. Body weight ranged between 8 g to 255.6 g (mean value = 87.76 ± 40.41 g). The exponent values (b slope) of lengthweight relationship of S. crumenophthalmus are 2.9838 for females and 2.7687 for males; indicating negative allometric growth pattern for both sexes. Synchronous reproductive behaviour was observed in both sexes and a pronounced peak of Gonadosomatic index was observed in females in January 2013. It is estimated that length at first maturity (L50) for females is at 19.39 cm FL and for males at 21.76 cm FL. Our result also suggest that big eye scad have a reduced swimming capability, resulting the species to be easily caught. Careful planning and management should be implemented to prevent the big eye scad from being overfished.

The importance of terrestrial insects as food items for freshwater fish was studied by examining stomach contents of Devario regina (Fowler 1934) and its population parameters at canopied areas of selected tributaries of Sungai Kerian, in the northern state of Peninsular Malaysia. Ninety six percent (121 out of 126) of the fish stomachs examined contained food materials in the stomachs and the values of percentage of occurrence (%F), percentage numerical (%N) and percentage points (%P) indicated that collected fish ate similar food items in all rivers. Among the food categories, scavenging terrestrial ants (Formicidae) were the most dominant food item, hence the main diet for this species. The Index of Relative Importance (IRI) scores of food items indicated that ants were higher than other food items. This surface water feeder experienced a positive allometric growth (W = aLb) with a b (rate of growth) value of 3.256. Its asymptotic length, growth constant and growth performance index represented this species with a short life-span (L∞ = 10.90 cm, K = 1.20 year-1, φ’ = 2.15, tmax = 3 year, respectively) and had higher natural mortality (M = 2.40 year-1) than fishing mortality (F = 0.35 year-1) while the fish stock was underexploited (E = 0.13). The finding of this study indicated the importance of terrestrial ants as a food source that support excellent growth of D. regina and the need to conserve riparian trees along river banks to provide allocthonous materials and habitats for the ants.

Gracilaria red algae are notable for their economic importance as agrophytes, sold as salad vegetable, and used as the base for selected food and nonalcoholic beverages. A wild population of Gracilaria exists in coastal areas of Sarawak, Malaysian Borneo, but there is only limited knowledge on species diversity and its abundance leaving the untapped economic potential of this resource. This study was carried out to determine diversity of wild Gracilaria populations in Lawas, Santubong, and Asajaya, Sarawak, using the combination of morphological character examination and 5′ region of the mitochondrial cytochrome c oxidase 1 (CO1-5P) gene analysis. Identification of the species using morphological characters revealed three species, namely, Gracilaria changii, G. blodgettii, and G. arcuata, had been collected from the sampling sites. However, based on 672 bp CO1-5P gene sequence analysis, all the three species were identified as G. blodgettii; besides, low genetic divergence values (0.17%–0.34%) were scored between samples in this study with the same species in GenBank. In the phylogenetic trees, all samples in this study group together with other G. blodgettii have high bootstrap values; thus, this species is monophyletic. This study implies that species identification of Gracilaria and other seagrass taxa which have a phenotypic plasticity problem should include the CO1-5P gene analysis as it is a reliable gene marker for species diversity assessment.

Although freshwater biomes cover less than 1% of the Earth's surface, they have disproportionate ecological significances. Attempts to study the taxonomy and function of freshwater microbiota are currently limited to samples collected from temperate lakes. In this study, we investigated samples from the photic and aphotic of an aquaculture site (disturbed) of Temengor Lake, a tropical lake in comparison with the undisturbed site of the lake using 16S rRNA amplicon and shotgun metagenomic approaches. Vertical changes in bacterial community composition and function of the Temengor Lake metagenomes were observed. The photic water layer of Temengor Lake was dominated by typical freshwater assemblages consisting of Proteobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, and Cyanobacteria lineages. On the other hand, the aphotic water featured in addition to Proteobacteria, Bacteroidetes, Verrucomicrobia, and two more abundant bacterial phyla that are typically ubiquitous in anoxic habitats (Chloroflexi and Firmicutes). The aphotic zone of Temengor Lake exhibited genetic potential for nitrogen and sulfur metabolisms for which terminal electron acceptors other than oxygen are used in the reactions. The aphotic water of the disturbed site also showed an overrepresentation of genes associated with the metabolism of carbohydrates, likely driven by the enrichment of nutrient resulting from aquaculture activities at the site. The results presented in this study can serve as a basis for understanding the structure and functional capacity of the microbial communities in the photic and aphotic zones/water layers of tropical man-made lakes.

Fish from three major rivers namely Pengkalan Chepa, Kelantan, and Galas rivers in Kelantan, Malaysia was caught using gill-nets with separate mesh sizes of 1, 2, 3, and 4 inches, respectively. There were 170 fish collected from the PCR systems, which represented 18 families and 21 species (2008-2009). The most common fishes, based on total fish captured, were Ikan duri (Arius maculatus) and Puyu (Anabas testudineus). A total of 245 individual fish were collected from KR (2010-2012) which comprised of 7 families and 22 fish species with the highest number of individual fish (51) collected during this survey was the spotted catfish (Arius maculatus). A total of 562 fish specimens representing 12 families and 32 species were captured from riverine monitoring in the GR systems (2008-2010).

Population Dynamics of Bigeye Scad, Selar crumenophthalmus in Bangaa Faru, Maldives Selar crumenophthalmus (bigeye scad) locally known as mushimas, is a widely distributed fish in Maldives. For the biological study, random samples of Selar crumenophthalmus (bigeye scad) were collected from September 2012 to February 2013. The samples were caught from Bangaa faru, in Male’ atoll, Maldives. A total of 1648 samples were collected, with their fork length ranging from 7.7 cm to 24.5 cm (16.85 ± 2.82 cm) and body weight ranging between 8g to 255.6 g (87.76 ± 40.41g). FiSAT software was used in estimating the population parameters.

Red seaweed Gracilaria sp. is known as ‘Janggut Duyong’ by the local people of Sarawak. This macroalgae iswell-distributed in both temperate and tropical seawaters. Gracilaria sp. could be processed to produce agar forindustrial purposes whereas some people consumed it directly and become part of their daily diet. In terms ofecology, Gracilaria sp. is one of primary producer in the seawater and its presence can form habitats to supportother aquatic organisms. Despite its socio-economic and ecological importance, little is known about Gracilariasp. in Sarawak. Hence, this study is designed to: (i) determine the diversity and abundance of Gracilaria in cageculture of Lawas, Sarawak (ii) assess the water quality of the cage culture area where Gracilaria is found and(iii) determine other aquatic organisms that found within Gracilaria population. Three field samplings had beenconducted from October 2013 to November 2014 at cage culture areas of Awat-Awat Village, Lawas, Sarawak.Only single species of Gracilaria was found namely Gracilaria arcuata. Besides G. arcuata, Acanthophora sp.and Padina sp. were also found but in small patches. In addition, five different groups of aquatic invertebrateswere observed namely tunicates, bivalves, polychaetes, small crabs and brittle stars. The selected water qualityparameters namely temperature, pH, dissolved oxygen, salinity, turbidity, total suspended solid, orthophosphate,silicate and chlorophyll a were significantly different (p= 0.000) during all the three field samplings except fornitrite (p= 0.588). However, the values recorded were within normal range of standard water quality for tropicalestuarine area. Since healthy population of Gracilaria could be easily found here, therefore this area has thepotential for future seaweed aquaculture.