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.
Asian arowana, Scleropages formosus is a highly valued aquarium fish in the world, particularly in Asian countries, and has been listed as one of the most highly endangered species. This is a freshwater, carnivorous, fairly large mouth breeding fish belonging to the family Osteoglossidae. Arowana can be found in different colour varieties such as green, red, silver and golden. Among these varieties, Malaysian golden is the most valuable fish and is endemic to the Krian riverine system, Malaysia. However, overexploitation, habitat change and pollution have caused a serious decline of this arowana variety. Recently, arowana aquaculture industry is expanding rapidly in Southeast Asian countries. However, difficulties in an accurate differentiation of sex and strains, causing imbalanced stocking ratios for optimum spawning, remain major obstacles in maximizing arowana production. In addition, problems in sustainable water sources of suitable quality and prevention of diseases need to be addressed. Recirculating aquaculture system (RAS) and bioremediation are two possible technologies that could be used to minimize pollution and ensure adequate high-quality water for arowana culture. In addition, the application of appropriate molecular markers for sex and strain identification is also an important strategy required for the improvement of captive breeding. This review discusses several issues such as the importance of arowana as an aquarium fish, its market demand, current problems in the arowana aquaculture industry and the possible technologies to enhance reproductive capacity and increase culture production. ?
Coupled behavioural observations and acoustical recordings of aggressive dyadic contests showed that the mudskipper Periophthalmodon septemradiatus communicates acoustically while out of water. An analysis of intraspecific variability showed that specific acoustic components may act as tags for individual recognition, further supporting the sounds' communicative value. A correlative analysis amongst acoustical properties and video-acoustical recordings in slow-motion supported first hypotheses on the emission mechanism. Acoustic transmission through the wet exposed substrate was also discussed. These observations were used to support an "exaptation hypothesis", i.e. the maintenance of key adaptations during the first stages of water-to-land vertebrate eco-evolutionary transitions (based on eco-evolutionary and palaeontological considerations), through a comparative bioacoustic analysis of aquatic and semiterrestrial gobiid taxa. In fact, a remarkable similarity was found between mudskipper vocalisations and those emitted by gobioids and other soniferous benthonic fishes.
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.
Samples of threadfin breams Nemipterus japonicus were collected from a village in Kuala Nyalau and a fish landing centre at Bintulu from April 2013 to March 2014. A total of 360 individuals of N. japonicus (214 male and 146 female) were used in this reproductive study.? The total length (TL) of individuals were measured to the nearest 0.1 cm and body weight (BW) was recorded to the nearest 0.1 g. Month-wise distribution of the sexes was significantly higher for males in September and March, while in the month of May the number of females was significantly higher (X(2) = 6.53; P < 0.05). Males showed a preponderance in the size-class of 19.0-20.9 cm (X(2) = 80.24; P < 0.001), 21.0 -22.9 cm (X(2) = 56.39; P < 0.001) and 23.0 -24.9 cm (X(2) = 17; P < 0.001). The gonadosomatic index (GSI) values of N. japonicus ranged from 0.07 to 0.19 for males and 0.34 to 4.99 for females. Females had higher GSI than males throughout the study period. For males, a higher GSI (0.11-0.19) was observed during January to February, while it was found to be higher (2.73-4.99) for females during January to March, indicating the spawning season. The present study revealed that ovarian maturity based on histological analysis of N. japonicus was classified into seven stages namely, immature (I), immature (II), maturing (III), mature (IV), ripe (V), spawning (VI) and spent (VII). The fecundity of N. japonicus was estimated to be within a range of 19221 to 85923 with higher GSI (3.08-6.78) from the coastal waters of Bintulu, Sarawak.
The stomach contents of Omobranchus sp. (family Blenniidae) larvae were investigated in a seagrass-mangrove based ecosystem in Johor Strait, Malaysia from October 2007 to September 2008. Specimens of larval fish were collected through subsurface towing of a Bongo net from five different stations. The stomach sacs of 267 Omobranchus sp. larvae were separated and observed, which comprised of 24 significant food stuffs belonging to 6 main groups viz. phytoplankton (62.45%), zooplankton (18.24%), algae (5.56%), plant-like particles (5.75%), debris (4.22%) and unidentified particles (2.03%). In situ water parameters were also measured throughout the sampling cruises. There was a strong and significant positive correlation between stomach phytoplankton and salinity (r = 0.658, p < 0.05).? Canonical correlation analysis indicated a weak relationship (29.8%) between stomach contents and physico-chemical parameters. Only salinity appeared to be the controlling factor for the stomach contents of Omobranchus sp. larvae in the investigated area. Based on the stomach content analysis, it could be concluded that Omobranchus sp. were mainly herbivorous during the larval stages. ?
Food production is a major driver of global environmental change and the overshoot of planetary sustainability boundaries. Greater affluence in developing nations and human population growth are also increasing demand for all foods, and for animal proteins in particular. Consequently, a growing body of literature calls for the sustainable intensification of food production, broadly defined as "producing more using less". Most assessments of the potential for sustainable intensification rely on only one or two indicators, meaning that ecological trade-offs among impact categories that occur as production intensifies may remain unaccounted for. The present study addresses this limitation using life cycle assessment (LCA) to quantify six local and global environmental consequences of intensifying aquaculture production in Bangladesh. Production data are from a unique survey of 2,678 farms, and results show multidirectional associations between the intensification of aquaculture production and its environmental impacts. Intensification (measured in material and economic output per unit primary area farmed) is positively correlated with acidification, eutrophication, and ecotoxicological impacts in aquatic ecosystems; negatively correlated with freshwater consumption; and indifferent with regard to global warming and land occupation. As production intensifies, the geographical locations of greenhouse gas (GHG) emissions, acidifying emissions, freshwater consumption, and land occupation shift from the immediate vicinity of the farm to more geographically dispersed telecoupled locations across the globe. Simple changes in fish farming technology and management practices that could help make the global transition to more intensive forms of aquaculture be more sustainable are identified.
While the ecological impact of anthropogenically introduced exotic species is considered a major threat for biodiversity and ecosystems functioning, it is generally not accounted for in the environmental life cycle assessment (LCA) of products. In this article, we propose a framework that includes exotic species introduction in an LCA context. We derived characterization factors for exotic fish species introduction related to the transport of goods across the Rhine-Main-Danube canal. These characterization factors are expressed as the potentially disappeared fraction (PDF) of native freshwater fish species in the rivers Rhine and Danube integrated over space and time per amount of goods transported (PDF·m(3)·yr·kg(-1)). Furthermore, we quantified the relative importance of exotic fish species introduction compared to other anthropogenic stressors in the freshwater environment (i.e., eutrophication, ecotoxicity, greenhouse gases, and water consumption) for transport of goods through the Rhine-Main-Danube waterway. We found that the introduction of exotic fish species contributed to 70-85% of the total freshwater ecosystem impact, depending on the distance that goods were transported. Our analysis showed that it is relevant and feasible to include the introduction of exotic species in an LCA framework. The proposed framework can be further extended by including the impacts of other exotic species groups, types of water bodies and pathways for introduction.
In this paper, a digital 3D model which allows for visualisation in three dimensions and interactive manipulation is explored as a tool to help us understand the structural morphology and elucidate the functions of morphological structures of fragile microorganisms which defy live studies. We developed a deformable generic 3D model of haptoral anchor of dactylogyridean monogeneans that can subsequently be deformed into different desired anchor shapes by using direct manipulation deformation technique. We used point primitives to construct the rectangular building blocks to develop our deformable 3D model. Point primitives are manually marked on a 2D illustration of an anchor on a Cartesian graph paper and a set of Cartesian coordinates for each point primitive is manually extracted from the graph paper. A Python script is then written in Blender to construct 3D rectangular building blocks based on the Cartesian coordinates. The rectangular building blocks are stacked on top or by the side of each other following their respective Cartesian coordinates of point primitive. More point primitives are added at the sites in the 3D model where more structural variations are likely to occur, in order to generate complex anchor structures. We used Catmull-Clark subdivision surface modifier to smoothen the surface and edge of the generic 3D model to obtain a smoother and more natural 3D shape and antialiasing option to reduce the jagged edges of the 3D model. This deformable generic 3D model can be deformed into different desired 3D anchor shapes through direct manipulation deformation technique by aligning the vertices (pilot points) of the newly developed deformable generic 3D model onto the 2D illustrations of the desired shapes and moving the vertices until the desire 3D shapes are formed. In this generic 3D model all the vertices present are deployed for displacement during deformation.
A study on diversity and distribution of fish communities and water qualities were carried out from January 2009 to December 2010 to cover monsoon and non-monsoon at Kuantan estuary, Pahang, Malaysia. A total of 19 species of primary marine fish belong to 12 families were recorded. Out of 311 individuals the fish fauna was dominated by Ariidae followed by Lutjanidae and Lactaridae. As such Ariidae contributes 50% of the fish caught in the study area and its diversity index (H') was 0.97. A The Ariidae family consist of four (4) species; Arius maculatus, Arius sumatranus, Arius tenuispinis and Arius thalassinus. The Ariidae family can be found in all stations as they are euryhaline (highly tolerant to salinity) and this fish family are known to be a hardy estuarine catfish. Among all species in family Ariidae, Arius thalassinus was the most dominant (23%) among all species. As such collected species showed highest species diversity (0.34) followed by Arius tenuispinis (0.25) compared to other species. Arius tenuispinis alone contributed 11.90% among the samples caught from all stations. The fishes were caught and recorded highest in September-December. Pseudorhombus quinque ocellatus, Nibea soldado, Sardinella fimbriata, Toxotes jaculatrix, Dasyatis ushiei, Setipinna taty were the least dominant in the Kuantan estuary with 9.33% of total abundance. Physico-temperatures, such as temperature (22.03-30 degrees C), Conductivity (10.342.43 mS cm(-1)), TDS (0.06-26.34 mg L(-1)), salinity (0.05-29.09 ppt), DO (6.37-8.38 mg L(-1)), pH (4.97-8.03), Chl a (0.01-1.33 microg L(-1)), nitrite (0.01-0.08 mg L(-1)), nitrate (0.60-0.88 mg L(-1)), phosphate (0.24-0.40 mg L(-1)). Nevertheless, the study envisages that the water quality and fish diversity are still conducive in the Kuantan estuary. The fish diversity of Pahang estuary was high monsoon compared to non-monsoons. The station 4 (LKIM fishing boat jetty and adjacent Hospital Kuantan) is the most polluted area due to the presence of several outskirts could be alarming for the sustainable development of fish and other aquatic organisms in Kuantan estuary in the long run.
To satisfy increasing demands for fish as food, progress must occur towards greater aquaculture productivity whilst retaining the wild and farmed genetic resources that underpin global fish production. We review the main selection methods that have been developed for genetic improvement in aquaculture, and discuss their virtues and shortcomings. Examples of the application of mass, cohort, within family, and combined between-family and within-family selection are given. In addition, we review the manner in which fish genetic resources can be lost at the intra-specific, species and ecosystem levels and discuss options to best prevent this. We illustrate that fundamental principles of genetic management are common in the implementation of both selective breeding and conservation programmes, and should be emphasized in capacity development efforts. We highlight the value of applied genetics approaches for increasing aquaculture productivity and the conservation of fish genetic resources.
Our previous study demonstrated that among different habitat sites (mangrove, estuary, river, seagrass and Open Sea) in Johor Strait, Malaysia, seagrass showed highest family diversity and abundance of larval fish. However, it is unclear whether this was due to difference in habitat complexity or water quality parameters.? To test this, larval fish were collected by using a bongo net equipped with a flow meter by subsurface horizontal towing from different habitats in Johor Strait between October 2007 and September 2008.? Various physico-chemical parameters were measured and then examined for any relationship to fish larvae diversity and abundance. Among the 24 families identified from the sites, seven families (Blenniidae, Clupeidae, Mullidae, Nemipteridae, Syngnathidae, Terapontidae and Uranoscopeidae) were significantly correlated with the tested waters quality parameters.? Salinity showed a positive and negative significant correlation with Clupeidae (p < 0.01) and Uranoscopeidae (p < 0.05), respectively. Terapontidae was significantly correlated with dissolved oxygen (p < 0.01), while both Mullidae and Syngnathidae were significantly correlated with pH (p < 0.05). However, a canonical correspondence analysis test indicated weak overall correlation (36.4%) between larval assemblage and in the seagrass-mangrove ecosystem of Johor Strait, Malaysia. This likely indicates that habitat structure was more important in determining larval abundance (highest in the seagrass habitat) as compared to water quality at the tested sites. This study emphasizes the need to conserve seagrass beds as important nursery grounds for various fish larvae to ensure adequate recruitment and ultimately sustainable fisheries management. ?
The anadromous Hilsa shad (Tenualosa ilisha) live in the Bay of Bengal and migrate to the estuaries and freshwater rivers for spawning and nursing of the juveniles. This has led to two pertinent questions: (i) do all Hilsa shad that migrate from marine to freshwater rivers come from the same population? and (ii) is there any relationship between adults and juveniles of a particular habitat? To address these questions, NextRAD sequencing was applied to genotype 31,276 single nucleotide polymorphism (SNP) loci for 180 individuals collected from six strategic locations of riverine, estuarine and marine habitats. FST OutFLANK approach identified 14,815 SNP loci as putatively neutral and 79 SNP loci as putatively adaptive. We observed that divergent local adaptations in differing environmental habitats have divided Hilsa shad into three genetically structured ecotypes: turbid freshwater (Western Riverine), clear freshwater (Eastern Riverine) and brackish-saline (Southern Estuarine-Marine). Our results also revealed that genes involved in neuronal activity may have facilitated the juveniles' Hilsa shad in returning to their respective natal rivers for spawning. This study emphasized the application of fundamental population genomics information in strategizing conservation and management of anadromous fish such as Hilsa shad that intersect diverse ecotypes during their life-history stages.
Kisspeptin and its cognate receptor, GPR54 (kisspeptin receptor, Kiss-R) have recently been recognized potent regulators of reproduction in vertebrates. In non-mammalian vertebrates, kisspeptin-Kiss-R homologous and paralogous genes have been identified with their conserved functions in reproduction. Teleosts possess two paralogous genes encoding kisspeptin (kiss1 and kiss2) and Kiss-R (kissr1 and kissr2). Identification of the location and the distribution of the kisspeptin-Kiss-R systems as well as their connectivity with other neural system in the brain is important to elucidate the role of kisspeptin in neuroendocrine functions. This review focuses on the comparative aspects of neuroanatomical distribution of two kisspeptin-Kiss-R systems in the brain of teleosts and their potential roles in reproductive and non-reproductive functions. Finally, based on the association of kisspeptin types with tachykinin peptides, their potential neuromodulatory roles in the brain of teleost will be discussed. The existence of two kisspeptin systems suggests their independent functions in the brain of teleosts. Understanding of teleosts Kiss1 and Kiss2 systems will provide insight into the physiological and evolutional significance of multiple kisspeptin systems in the vertebrate brain.
In order to understand feeding ecology and habitat use of coral reef fish, fatty acid composition was examined in five coral reef fishes, Thalassoma lunare, Lutjanus lutjanus, Abudefduf bengalensis, Scarus rivulatus and Scolopsis affinis collected in the Bidong Island of Malaysian South China Sea.
Morphological identification of fish taxa can sometimes prove difficult because phenotypic variation is either being affected by environmental factors, phenotypic characters are highly conserved or marker selection has been inappropriate. DNA based markers especially neutral mitochondrial DNA (mtDNA) have been used widely in recent times to provide better resolution of systematic relationships among vertebrate taxa. The Asian Arowana (Scleropages formosus) is a high value ornamental fish belonging to the family Osteoglossidae with a number of different colour variants distributed geographically across different locations around Southeast Asia. Systematic relationships among colour variants still remain unresolved. Partial sequences of the Cytochrome B (Cyt B) and DNA barcoding gene, Cytochrome C Oxidase I (COI) were used here to assess genetic relationships among colour variants and as a tool for molecular identification for differentiating among colour variants in this species. Results of the study show that in general, colour pattern shows no relationship with extent of COI or Cyt B mtDNA differentiation and so cannot be used to identify taxa. Partial sequences of the mtDNA genes were sufficient however, to identify S. formosus from a closely related species within the order Osteoglossidae.
Population growth, trophic level, and some aspects of reproductive biology of two congeneric archer fish species, Toxotes chatareus and Toxotes jaculatrix, collected from Johor coastal waters, Malaysia, were studied. Growth pattern by length-weight relationship (W=aL(b)) for the sexes differed, and exhibited positive allometric growth (male, female and combined sexes of T. chatareus; female and combined sexes of T. jaculatrix) and isometric growth (male samples of T. jaculatrix only). Trophic levels of both species were analyzed based on 128 specimens. The results show that, in both species, crustaceans and insects were the most abundant prey items, and among crustaceans the red clawed crab Sesarma bidens and Formicidae family insects were the most represented taxa. The estimated mean trophic levels for T. chatareus and T. jaculatrix were 3.422+/-0.009 and 3.420+/-0.020, respectively, indicating that they are largely carnivores. Fecundity of T. chatareus ranged from 38 354 to 147 185 eggs for females with total length ranging from 14.5 to 22.5 cm and total body weight from 48.7 to 270.2 g, and T. jaculatrix 25 251 to 150 456 eggs for females with total length ranging from 12.2 to 23.0 cm and total body weight from 25.7 to 275.0 g. Differences in values of gonadosomatic and hepatosomatic indexes calculated for both species in this study may have resulted from uneven sample size ranges.
The first phase of toxicity identification evaluation (TIE) method comprised of physic-chemical fractionation steps of pH adjustment, pH adjustment followed by filtration, aeration, extraction with solid phase C18 column (SPE), oxidant reduction with sodium thiosulphate and EDTA chelation was conducted to characterize the toxicants of a Malaysian landfill leachate. The battery of organisms test chosen were freshwater fish (Rasbora sumatrana), freshwater prawn (Macrobrachium lanchesteri) and tomato seed (Lycoperson esculentum). Toxicity reductions at each step were comparable for all test organisms. The major toxicants present in the leachate were found to be mostly basic in nature and precipitable under acidic conditions as well as containing non-polar organic compounds. A small reduction in toxicity was observed when leachate was treated with sodium thiosulphate in oxidant reduction test indicating the presence of oxidizers. The EDTA chelating step did not significantly reduce toxicity in the test organisms suggesting insignificant level of (toxic) metals.
A total of 58 Gram-positive bacteria strains were isolated from the marine environment and screened for potential probiotics for disease prevention and improving the productivity of tiger grouper Epinephelus fuscoguttatus larvae and juveniles. The bacteria were identified as Bacillus licheniformis, B. subtilis, B. circulans, B. sphaericus, B. cereus, Brevibacillus brevis, Corynebacterium propinquum, Leifsonia aquatica and Paenibacillus macerans. Only 24 strains showed antagonistic activities against four pathogenic strains; Vibrio alginolyticus, V. harveyi, V. parahaemolyticus and Aeromonas hydrophila, where two of the Bacillus strains, B12 and B45 demonstrated intermediate to highest level of inhibitory activity against these pathogenic strains, respectively. Further assessment by co-culture assay showed that Bacillus strain B12 exhibited a total inhibition of V. alginolyticus, while B45 strain displayed no inhibitory activity. Mixed culture of Bacillus B12 and B45 strains to outcompete V. alginolyticus was observed at a cell density of 10(7) CFU ml(-1). Molecular identification and phylogenetic tree analysis have categorized Bacillus strain B12 to the reference strains GQ340480 and JX290193 of? B. amyloliquafaciens, and Bacillus strain B45 with a reference strain JF496522 of B. subtilis. Safety tests of probionts by intraperitoneal administration of B12 and B45 strains at cell densities of 103, 105 and 10(7) CFU ml(-1) revealed no abnormalities and cent percent survival for healthy Epinephelus fuscoguttatus juveniles within 15 days of experimental period. Overall, the study revealed that Bacillus B12 strain possesses tremendous probiotic potential that could be used as a feed supplement in tiger grouper diets. ?
Oxyeleotris marmorata is an ambush predator. It is known for slow growth rate and high market demand. Farming of O. marmorata still remains a challenge. In order to establish a proper feeding practice to stimulate growth, knowledge of its metabolic processes and cost should be examined. Therefore, this study was designed to investigate the diel osmorespiration rhythms of O. marmorata in response to feeding challenge by using an osmorespirometry assay. The results have shown that oxygen consumption rate of the fed fish was approximately 3 times higher than that of the unfed fish in early evening to support specific dynamic action. Digestion and ingestion processes were likely to be completed within 18-20 h in parallel with the ammonia excretion noticeable in early morning. Under resting metabolism, metabolic oxygen consumption was influenced by diel phase, but no effect was noted in ammonia excretion. As a nocturnal species, O. marmorata exhibited standard aerobic metabolic mode under dark phase followed by light phase, with high oxygen consumption rate found in either fed or unfed fish. It can be confirmed that both the diel phase and feeding have a significant interactive impact on oxygen consumption rate, whereas ammonia metabolism is impacted by feeding state. High metabolic rate of O. marmorata supports the nocturnal foraging activity in this fish. This finding suggested that feeding of O. marmorata should be performed during nighttime and water renewal should be conducted during daytime.