Effect of salinities on gastric emptying and nutrient absorption of tiger grouper × giant grouper (Epinephelus fuscoguttatus × E. lanceolatus) hybrid

The effects of salinity on the gastric emptying time (GET) and absorption of nutrient along the alimentary tract of tiger grouper (TG) × giant grouper (GG) (Epinephelus fuscoguttatus × E. lanceolatus) hybrid were studied. Juveniles TG×GG hybrid grouper (10.0 ± 0.5 cm total length; 50.5 ± 2.0 g) were reared in different salinities (10, 15, 20, 25 and 30 parts per thousand (ppt)) and fed with commercial pellet diet during the 60-day experimental period. The fish were then slaughtered sequentially at different time intervals after initial feeding to obtain GET. Our results showed that low salinity (10-20 ppt) lead to a shorter GET in the hybrid grouper. The shortest and longest GETs were observed in 15 ppt (12 h) and 30 ppt (18 h) treatments, respectively. Apparent digestibility coefficient (ADC) using ash contents was measured to determine the absorption of nutrient in each treatment. The absorption of macronutrient in TG×GG hybrid grouper was increased as the salinity decreased. The highest absorption occurred in 15 ppt (72% protein, 75% lipid, 68% carbohydrate and 74% energy) while the lowest absorption occurred in 30 ppt (59% protein, 64% lipid, 34% carbohydrate and 55% energy). The findings of this study suggested that 15 ppt salinity facilitates faster digestion and maximize the nutrient absorption of TG×GG hybrid and may enhance the growth rate of this newly developed grouper species

Fenomena El Niño dan impak terhadap hasil tangkapan ikan: kajian kes di Sabah, Malaysia

Kesan fenomena El Niño Southern Oscillation (ENSO) berbeza-beza bergantung kepada lokasi dan ia telah menyebabkan berlakunya dapatan kajian yang berbeza dalam bidang perikanan. Kajian ini bertujuan mengkaji fenomena El Nino dan impak terhadap taburan kepekatan klorofil di perairan Pantai Barat Sabah, dan pengaruhnya terhadap tangkapan ikan pada tahun 2015/2016. Kajian ini menggunakan maklumat data daripada satelit penderiaan jauh MODIS bagi tahun 2012 hingga tahun 2016 bagi memetakan taburan kepekatan kandungan klorofill. Kajian ini juga menggunakan maklumat data tangkapan ikan yang diperoleh daripada Jabatan Perikanan Negeri Sabah dan maklumat data Oceanic Niño Index (ONI). Hasil kajian mendapati penurunan hasil tangkapan ikan semasa fenomena El Niño pada tahun 2015/2016.Hasil kajian mendapati fenomena El Niño mempengaruhi hasil tangkapan ikan dan kandungan klorofil yang tentunya memberi kesan terhadap jumlah pendapatan nelayan dan industri yang berikatan

Effects of quorum sensing and its degrader on the virulence of vibrio harveyi towards tiger grouper, Epinephelus fuscoguttatus Forsskal larvae

Quorum sensing (QS) is a bacterial cell-to-cell communication with small signal molecules such as acyl-homoserine lactones (AHL) that control a number of phenotypes including the regulation of virulence determinants in pathogenic bacteria. Therefore, quorum sensing degrader has been suggested as one of the biocontrol strategy to fight bacterial infections as an alternative to the use of antibiotics. In this study, the link between quorum sensing (QS) in Vibrio harveyi and its virulence towards tiger grouper (Epinephelus fuscoguttatus) were investigated. The virulence activity was studied using V. harveyi wild type and its QS mutants with constitutively maximal or minimal quorum sensing activity and different signal molecule (autoinducer) synthase gene mutants. The potential of live feed Artemia as the carrier of bacterial quorum sensing degrader for the tiger grouper larvae was also investigated. The results showed that the wild type Vibrio harveyi BB120 was pathogenic to grouper (Epinephelus fuscogutattus) larvae causing more than 50% larval mortality after four days of challenge. Furthermore, the mortality of grouper larvae challenged withV. harveyimutant JAF483 with maximally active QS (QS+) was significantly higher than the V. harveyiwild type BB120. Meanwhile, high survival was observed in the grouper larvae challenged to JAF548 with minimally active QS (QS-) compared to the JAF483 (QS+). High survival of larvae were also observed in the QS autoinducer mutant strains of JMH634 (QS triple autoinducer synthase mutant),BB152 (Harveyi autoinducer-1 (HAI-1) synthase mutant) and MM30 (Autoinducer-2 (AI-2) synthase mutant). In contrast, low survival was observed in the strain JMH603 (Cholerae autoinducer-1 (CAI-1) synthase mutant). This indicated that the HAI-1 and AI-2 QS signal molecules might play important roles for the virulence of V. harveyi towards grouper larvae but not CAI-1. To support this, addition of HAI-1 in the water restored the virulence of the mutant. The effects of the infection on the larvae could also be seen histologically. In addition, the in vivo expression data showed that the HAI-1 signal molecule upregulated the innate immune genes consisting of tripartite motif-containing protein 39 (TRIM39), Hepcidin-1 (Hep-1), peptidoglycan recognition protein SC2 (PGRP) and toll like receptor 5 (TLR5) at different hours compared to control. The expression of both control and the bacterial mutant BB152 without HAI-molecules remained low throughout the experimental period. Next, different bacterial QS degrader strains were isolated from Artemia and screened using Chromobacterium violaceum CV026 bioassay. The results showed six bacterial strains (four Gram-positive and two Gramnegative) isolated from Artemia are able to degrade AHL in two different in vitro assays. The highest bacterial AHL degrader, identified as Bacillus litoralis BP-ART/6 fully degraded 10 ppm AHL from 9 hours. Encapsulation of the Bacillus strain to Artemia also significantly improve the survival and total length of the live feedcompared to control without addition of any bacteria. This study showed that bacterial strain isolated from Artemia can act as a quorum sensing degrader and can be encapsulated to Artemia. It was later observed that B. litoralis could also be used as probiotic bacteria administered through Artemia nauplii to protect grouper larvae against infection of V. harveyi

Towards Sustainable Aquaculture: A Brief Look into Management Issues

Aquaculture’s role has expanded over the past two decades, with the industry contributing to nearly 50% of the overall fish production. Aquaculture production in Asia and Africa contributes a significant share of total global aquaculture output growth. Aquaculture supports livelihoods and income improvement in a number of states, despite the fact that economic situations have indeed been unfavourable and environmental concerns remain undeniable. To meet the growing demand for fish, aquaculture must expand. However, this expansion will not be sustainable unless management and planning are significantly improved. Local, national, and international management are needed to address the social, economic, and environmental problems. These provide the foundation to proper aquaculture management strategies. In considering the involved ecology, water quality, and genetics, aquaculture can have a detrimental impact on the environmental sustainability. This paper highlights the review on site selection with capacity evaluation, analysis of threats and risks, as well as certification and standards, which are all important considerations in achieving a sustainable aquaculture industry

Coastal Vulnerability: A Brief Review on Integrated Assessment in Southeast Asia

Coastal zones are an essential part of maintaining sustainability in the world. Coastal regions have gained importance due to various factors, including high ecological production, dense population, industry compatibility, waste disposal, leisure, transportation, and development of military strategies. Coasts are often on the move and must adapt while nature constantly works to maintain balance. Southeast Asia has gained prominence due to its rich ecosystem, high productivity, and densely populated coastal region. In light of this, the coastlines of Southeast Asia are threatened by various factors, including global climate change and human activities. These factors exacerbate the shoreline erosion, frequent catastrophic events, rising sea levels, and saltwater intrusion. Coastal management has become one of the most important challenges of the past decade. The coastal vulnerability index (CVI) was developed to identify and manage vulnerable locations along the coast. Thus, this review attempts to summarize coastal vulnerability in Southeast Asian based on journals and reports. Topics covered include: (1) introduction to coastal vulnerability, (2) methods for determining coastal vulnerability, (3) factors influencing coastal vulnerability (4) associated coastal vulnerability, (5) assessment gaps, and (6) further courses of action. Consequently, assessment of coastal vulnerability will support Southeast Asian coastal communities in guiding mitigation strategies to manage coastal threats in future climate change and urban development

Coastal Vulnerability: A Brief Review on Integrated Assessment in Southeast Asia

Coastal zones are an essential part of maintaining sustainability in the world. Coastal regions have gained importance due to various factors, including high ecological production, dense population, industry compatibility, waste disposal, leisure, transportation, and development of military strategies. Coasts are often on the move and must adapt while nature constantly works to maintain balance. Southeast Asia has gained prominence due to its rich ecosystem, high productivity, and densely populated coastal region. In light of this, the coastlines of Southeast Asia are threatened by various factors, including global climate change and human activities. These factors exacerbate the shoreline erosion, frequent catastrophic events, rising sea levels, and saltwater intrusion. Coastal management has become one of the most important challenges of the past decade. The coastal vulnerability index (CVI) was developed to identify and manage vulnerable locations along the coast. Thus, this review attempts to summarize coastal vulnerability in Southeast Asian based on journals and reports. Topics covered include: (1) introduction to coastal vulnerability, (2) methods for determining coastal vulnerability, (3) factors influencing coastal vulnerability (4) associated coastal vulnerability, (5) assessment gaps, and (6) further courses of action. Consequently, assessment of coastal vulnerability will support Southeast Asian coastal communities in guiding mitigation strategies to manage coastal threats in future climate change and urban development

Effect of stocking density on the growth, body composition, and blood parameters of cage-reared Gangetic mystus catfish (Mystus cavasius)

Suitable stocking density of Gulsa tengra (Mystus cavasius) was observed by measuring growth performance, production, and survival in nylon net cages for 120 days in Chalan Beel floodplain ecosystem. Fry of Gulsha tengra (5.55 ± 0.49 g in weight) were stocked into 6 × 3 × 2-m (36 m3) floating net cages with treatments: T1-50, T2-100, T3-150, and T4-200 fry/m3 (in triplicates). The stocked fry was fed twice daily with commercial floating pellet containing 32 % protein at the rate of 5 % /fish body weight during the first 2 months and then reduced to 3 % for the next 2 months. The highest weight gain was observed in the lowest density treatment, T1 (18.70 ± 1.37 g) and the lowest (8.66 ± 0.99 g) in highest density treatment, T4 (all tests for significance were performed at a 5 % level). The rate of survival varied from 86.6 % and 95.8 %, with T1 resulting in the significantly highest survival. A better feed conversion ratio was also observed in T1 (1.75 ± 0.26). Significantly higher protein (16.86 ± 0.36) and fat (2.78 ± 0.02) contents were recorded in the fish body composition in T1. Water quality parameters (temperature: 26.0 ± 1.0 °C, pH: 7.2 ± 0.2, DO: 6.4 ± 0.1 mg/l, NH3-N: 0.002 ± 0.001) recorded throughout the study period were within the suitable range for fish culture. The highest red (119.0 ± 4.85 ×106 µl) and white blood cell (233.2 ± 16.02 ×103 µl), hemoglobin (5.65 ± 0.30 g/dl), total protein (5.50 ± 0.03 g/dl), albumin (1.82 ± 0.06 g/dl), and globulin (3.65 ± 0.15 g/dl) were also observed in T1 indicating optimum condition. Total and net production per cage were the highest in T1 with approximately 50 % increase (88.31 ± 6.72 and 59.27 ± 5.79 kg, respectively) compared to T4. The net income and benefit–cost ratio was increased by approximately 42 % and 30 %, respectively, in T1. Thus, this study recommended an optimal stocking density of 50 fish/m3 for Gulsha tengra to achieve a profitable and robust yield in cage culture

Elevated Carbon Dioxide and Its Impact on Growth, Blood Properties, and Vertebral Column of Freshwater Fish Mahseer, <i>Tor tambroides</i> Juveniles

The level of carbon dioxide, which resembles water acidification, is critical to the success of juvenile fish production. The growth, skeletal deformities, and blood parameters of the economically important freshwater fish mahseer, Tor tambroides, were assessed in different concentrations of pCO2 (400, 700, and 1000 µatm pCO2). The highest growth properties (survival rate, body weight gain (BWG), specific growth rate (SGR)) in mahseer were observed at 400 µatm, whereas the lowest growth indices were found in the treatment of 1000 µatm pCO2. The lowest pCO2 concentration was found to be within the optimum healthy blood parameter range. The fish exposed to acidic conditions (700 and 1000 µatm) exhibited considerably higher levels of haemoglobin and haematocrit compared to the control fish. Glucose levels were significantly lower in the acidic conditions, while total cholesterol levels in mahseer fish exposed to acidic conditions were higher. The fish displayed skeleton malformations as the concentration of pCO2 was elevated. The findings from this research could be set as a standard technique in the juvenile rearing of mahseer fish under acidified conditions

Length-weight relationship, condition factor, and age estimation of commercially important trawl species from Mersing coastal waters, Johor, Malaysia

Trawl fishing contributes to majority of the total fishes’ landings, supporting the choice of using age, growth determination, and condition factors (K) as part of the monitoring method for the fishes in Malaysia waters. This research specifically examines the use of age, length-weight relationship (LWR), and K to monitor the status of the commercially important fishes in Malaysia waters. LWR, K, and age of 10 commercially important trawl species (Gerres erythrourus, Drepane punctata, Otolithes ruber, Anodontostoma chacunda, Drepane longimana, Dendrophysa russelii, Sillago parvisquamis, Cynoglossus bilineatus, Sardinella brachysoma, and Alepes kleinii) from Mersing coastal waters, Johor, Malaysia, were studied. LWR (W=aLb ) indicated positive allometric growth (b > 3) for G. erythrourus and D. punctata but negative allometric growth (b < 3) for the other species. Results indicated that the species collected were in good conditions (average K, Kn > 1) in Mersing coastal waters, Johor, Malaysia. The daily growth rings of scale counts confirmed that the ages of the 10 species were typically less than 1 year (age range: 50-170 days; mean age: 95 days). The data obtained from this study will be useful for understanding the population growth pattern, age, and well�being of commercially important trawl species, which will facilitate better management techniques of these important fishery resources

Quorum sensing is required for full virulence of Vibrio campbellii towards tiger grouper (Epinephelus fuscoguttatus) larvae

The link between quorum sensing in Vibrio campbellii and its virulence towards tiger grouper (Epinephelus fuscoguttatus) was investigated using V. campbellii wild type and quorum-sensing mutants with inactive quorum sensing or constitutively maximal quorum-sensing activity, and signal molecule synthase mutants. The results showed that wild-type V. campbellii is pathogenic to grouper larvae, causing more than 50% mortality after 4 days of challenge. Furthermore, the mortality of larvae challenged with the mutant with maximally active quorum sensing was significantly higher than that of larvae challenged with the wild type, whereas a higher survival was observed in the larvae challenged to the mutant with a completely inactive quorum-sensing system. Grouper larvae challenged with either the signal molecule synthase triple mutant, the harveyi autoinducer-1 (HAI-1) synthase mutant and the autoinducer-2 (AI-2) synthase mutant showed higher survival than larvae challenged with the wild type. In contrast, larvae challenged with the cholerae autoinducer-1 (CAI-1) synthase mutant showed high mortality. This indicates that HAI-1 and AI-2, but not CAI-1, are required for full virulence of V. campbellii towards grouper larvae. Our data suggest that quorum-sensing inhibition could be an effective strategy to control V. campbellii infections in tiger grouper