Asian Sea Research Articles

The effects of probiotics‐supplemented diets on Asian sea bass ( Lates calcarifer ): Growth performance, microbial flora, digestive enzymes activity, serum biochemical and non‐specific immune indices

The effects of probiotics‐supplemented diets on Asian sea bass ( <i>Lates calcarifer</i> ): Growth performance, microbial flora, digestive enzymes activity, serum biochemical and non‐specific immune indices

Perfluoroalkyl substances in freshwater and marine fish from northern Vietnam: Accumulation levels, profiles, and implications for human consumption

The accumulation profiles of nine perfluoroalkyl substances (PFASs) were determined in 95 muscle samples of seven freshwater (n = 65) and seven marine (n = 30) fish species collected in Northern Vietnam. In both groups of fish, perfluorooctane sulfonic acid (PFOS) was the most prevalent component, accounting for roughly 29 % of total PFASs. The total PFASs in freshwater fish species ranged from 0.08 to 8.06 ng/g wet weight (w.w), with the highest concentration found in topmouth culter (7.01 ± 1.23 ng/g w.w). In marine fish, the highest mean concentration of PFASs was detected in Asian sea bass (2.75 ± 0.54 ng/g, w.w). Estimation on the human dietary intake of PFASs from fish consumption resulted in hazard ratios (HR) ranging from 0.019 to 0.238 for freshwater fish and from 0.016 to 0.074 for marine fish, indicating low exposure risks associated with PFASs.

Development of aeration devices and feeding frequencies for oxygen concentration improvement in 60-tones freshwater recirculating aquaculture and biofloc ponds of Asian seabass (Lates calcarifer) rearing

This research aimed to improve the technique to maintain the oxygen content of two freshwater Asian sea bass (Lates calcarifer) culture systems (recirculating aquaculture system; RAS; and biofloc system; Floc). The dissolved oxygen content was increased by using a blower with flexible rubber hose aerators. For the first study, the effectiveness of oxygenation was investigated. As a result, the aerator and flexible rubber hose are appropriate for increasing oxygen levels in the fish pond. An air pump with a flexible aeration tube (400 W), one set of ejector aerators (250 W), and two sets of ejector aerators (250 × 2 W) were used to test the efficiency of oxygenation. In addition, the performance of the RAS and Floc systems, off-flavor (geosmin and MIB) in taints, and economic returns were assessed. This study found that after monitoring two 60-tonne concrete ponds with one set of blowers (RAS1) and two sets of blowers (RAS2) connected by a flexible rubber tube; feeding frequency (2 and 6 times/day). However, daily dissolved oxygen fluctuated in the RAS, and this value went to its lowest after post-feeding. Dissolved oxygen was higher than the two-meal pack per day when the feeding was expanded to six meals. This aeration device could provide dissolved oxygen enough for 900 kg fish/400 W. Seabass raised in the freshwater RAS system had higher yields and growth rates than those raised in the biofloc pond systems. In addition, low off-flavors trained was observed. Therefore, this research could improve aeration management by aeration devices and increase feeding frequency while developing freshwater-adapted Asian seabass production.

History of coastal dune evolution in the Fujian region of southeastern China over the last millenium

Coastal dunes are a product of the evolution of the coastal environment. Previous research shows that dune development in the Fujian coastal region correlates well with the fluctuations of East Asian winter monsoon (EAWM) and sea level. However, comparison of coastal dune evolution along the Fujian coast since 1 ka with various paleoenvironmental indicators shows that, in addition to EAWM and sea level change, increased frequency and intensity of typhoon landfalls and tropical cyclone may have played an important role in dune building. Here we present the results of optically stimulated luminescence (OSL) dating and analyses of lithostratigraphy, grain size, and color of late Holocene aeolian sediments from Shenhu Bay of the Fujian coast, Southeastern China. Together with published chronological data from the region, three phases of coastal aeolian activity are defined: ~1050–1300 CE (the Medieval Climatic Anomaly, MCA), ~1450–1700 CE (early Little Ice Age, LIA), and ~ 1750–1930 CE (late LIA). These phases of sand accumulation had different sand sources: the source for the two phases of ~1050–1300 CE and ~ 1450–1700 CE was the reworking of the adjacent “old red sand”, and that for the phase of ~1750–1930 CE was beach and/or foredune sand. During ~1050–1300 CE, although the sea level was relatively high and the beach sand source was relatively limited, the increased frequency of typhoon landfalls and the widely distributed “old red sand” deposits provided important dynamic and provenance conditions for the formation of coastal dunes. During ~1450–1700 CE, strong EAWM and increased frequency of typhoon landfalls were all conducive to aeolian activities. On the contrary, the strong aeolian activity during ~1750–1930 CE may be related to sea level drop and strong EAWM.

Summaries

Summaries

Then What? Assessing the Military Implications of Chinese Control of Taiwan

Abstract The military implications of Chinese control of Taiwan are understudied. Chinese control of Taiwan would likely improve the military balance in China's favor because of reunification's positive impact on Chinese submarine warfare and ocean surveillance capabilities. Basing Chinese submarine warfare assets on Taiwan would increase the vulnerability of U.S. surface forces to attack during a crisis, reduce the attrition rate of Chinese submarines during a war, and likely increase the number of submarine attack opportunities against U.S. surface combatants. Furthermore, placing hydrophone arrays off Taiwan's coasts for ocean surveillance would forge a critical missing link in China's kill chain for long-range attacks. This outcome could push the United States toward anti-satellite warfare that it might otherwise avoid, or it could force the U.S. Navy into narrower parts of the Philippine Sea. Finally, over the long term, if China were to develop a large fleet of truly quiet nuclear attack submarines and ballistic missile submarines, basing them on Taiwan would provide it with additional advantages. Specifically, such basing would enable China to both threaten Northeast Asian sea lanes of communication and strengthen its sea-based nuclear deterrent in ways that it is otherwise unlikely to be able to do. These findings have important implications for U.S. operational planning, policy, and grand strategy.

Mucoadhesive cationic lipid-based Flavobacterium oreochromis nanoencapsulation enhanced the efficacy of mucoadhesive immersion vaccination against columnaris disease and strengthened immunity in Asian sea bass (Lates calcarifer)

Columnaris is a bacterial disease, found in freshwater fish, caused by Flavobacterium oreochromis. The disease has a devastating impact on a range of cultured and wild freshwater fish species e.g. Lates calcarifer (Asian sea bass), which is a serious economic losses to the freshwater aquaculture in Thailand. The disease can be prevented by an efficacious vaccine, however, no licensed effective vaccine is available to date. Current study was based on the development of a novel mucoadhesive nano-encapsulated vaccine (EncapFlavoNP++), where, cationic lipid-based nanoparticles were combined with an antigen obtained from F. oreochromis. Various parameters including transmission electron microscopy (TEM), physiochemical properties; zeta potential, and polydispersity index were determined. The TEM results depicted well-formed circular-shaped nano-encapsulates complexed with cationic lipid surfactants. The average diameter of the molecules was 200 nm, having a zeta potential of 31.82 mV, while, the polydispersity index (PDI) was 0.31. The in vivo study lasted for 8 weeks, the immunologic and protective potentials of the prepared molecules were determined by challenging the fish for 8 weeks. The most effective dilutions of EncapFlavoNP++ solution were 1:100 and 1:200, which significantly improved the efficacy of the immunity by increasing the level of antibody specific to F. oreochromis. A trend of upregulation was found in the immune-related genes including immunoglobulin M heavy chain (IgM), major histocompatibility complex class IIα molecules (MHC-IIα), and dendritic cell specific transcript (DCs) in gills, skin, liver, peripheral blood lymphocytes (PBLs), head kidneys, and spleen as compared to the control group (P < 0.05 and P < 0.01). Upon immunization with EncapFlavoNP++ solution at the dilution of 1:100 and 1:200, the significant increase in survival rate (SR) and relative percent survival (RPS) were found in fish challenged with virulent F. oreochromis bacterium (SR 72.50% and RPS 62.07) and (SR 65.83% and RPS 52.87), respectively as compared to the control group (P < 0.05). It can be concluded that immunization with EncapFlavoNP++ solution has significant immunologic and protective effects against Columnaris disease. Furthermore, the prepared vaccine candidate has more potential as compared to whole-cell immersion vaccination (FK-WC). It can be used on a large scale in the freshwater aquaculture industry to boost immunity against Columnaris disease.

Soluble Asian sea bass bone bio‐calcium: characteristics, bioavailability across Caco‐2 cells and fortification into apple juice

SummarySoluble Asian sea bass bone bio‐calcium (SBC) prepared using citric acid was characterised and examined for bioavailability. SBC showed lower calcium content (9.12%) but higher solubility (74.56%) in in vitro gastrointestinal tract system, compared to bio‐calcium. Calcium bioavailability of bio‐calcium across Caco‐2 cells was higher than that of SBC. SBC showed slightly lower L*, b* and ΔE*‐values with higher a*‐values than that of bio‐calcium. Fortification of SBC at various levels (0, 0.5, 1, 1.5 and 2%, w/v) into apple juice was also carried out. Apple juice fortified with SBC at various levels showed differences in pH, turbidity, brown colour and calcium content. The increased SBC levels resulted in lower pH, but higher turbidity, brown colour and calcium content. SBC fortification had no effect on likeness score for appearance, colour, odour and sandy mouthfeel. Nevertheless, flavour, taste and overall likeness of apple juice decreased when SBC added was increased. Calcium content of apple juice fortified with SBC up to 1% was increased by 6.13‐fold with no sensory effects.

Distribution of Vibrionaceae in farmed Asian sea bass, Lates calcarifer in Thailand and their high prevalence of antimicrobial resistance

This study describes the etiological agent of Vibriosis along with its distribution and antimicrobial resistance profiles among farmed Asian sea bass (Lates calcarifer) in Thailand. The study isolated 283 Vibrionaceae from 15 Asian sea bass farms located around the provinces of the Andaman Sea and Gulf of Thailand coasts to uncover the distribution and antimicrobial resistance profiles. Bacterial identification based on a combination of the biochemical characteristics, Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) analysis, and the species-specific PCR demonstrated the predominant Vibrionaceae were Vibrio harveyi (n=56), Photobacterium damselae (n=35), and V. vulnificus (n=31), respectively. According to a laboratory challenge experiment, among the six isolates, only V. harveyi was found to cause clinical signs of muscle necrosis and scale loss in Asian sea bass. Antibiotics resistance test results exhibited high resistance to antibiotics such as metronidazole (100%), streptomycin (97%), clindamycin (96%), colistin sulphate (70%) and amoxicillin (59%). Remarkably, 100% of Vibrionaceae isolates are susceptible to florfenicol. The 28 of 29 resistance profiles were multidrug resistances (MDR), with V. vulnificus having the highest MAR value (0.66). The findings of this study advise that a surveillance program, as well as preventive and control measures, be developed for Vibrionaceae to reduce production loss, pathogen proliferation, and antibiotic abuse, whereas AMR data indicate substantial health problems for aquatic animals and humans.

Effects of dietary tuna hydrolysate supplementation on feed intake, growth performance, feed utilization and health status of Asian sea bass ( Lates calcarifer ) fed a low fish meal soybean meal‐based diet

This study aimed to examine the effects of dietary tuna hydrolysate supplementation on feed intake, growth, feed utilization and health status of Asian sea bass. Experimental diets included a high fish meal-based diet (HFM diet) containing 45% of fish meal, a low fish meal-based diet (LFM diet) in which 55% of fish meal protein was replaced with soybean meal and the LFM diet coated with 2.5% tuna hydrolysate (LFM + TH diet). Fish were fed diets for 8 weeks. Growth rate, feed intake, feed efficiency, protein efficiency ratio, nitrogen retention, intraperitoneal fat and serum albumin of fish-fed LFM + TH diet were significantly higher than those of fish-fed LFM diet (p < 0.05). No significant differences in carcass chemical compositions, serum cholesterol, triglyceride, aspartate aminotransferase, lysozyme activity, superoxide dismutase and trypsin and lipase activities were found in hepatopancreas and anterior intestine among the dietary treatments. Fish-fed LFM + TH diet displayed a longer length of distal intestine villi than those of fish-fed LFM + TH diet. No histopathological changes in the liver were observed in this study. The results suggest that dietary supplementation of 2.5% tuna hydrolysate is sufficient to enhance the diet palatability, which can increase the replacement levels of fish meal protein with soybean meal up to 55% in a low fish meal soybean meal-based diet without negative impacts on feed intake and growth performance of juvenile Asian sea bass.

Combined effects of prior plasma-activated water soaking and whey protein isolate-ginger extract coating on the cold storage stability of Asian sea bass (Lates calcarifer) steak

The combination of prior plasma-activated water soaking (PS) before whey protein isolate-crude ginger extract coating (WC) on the cold storage stability (4 °C) of Asian sea bass steaks (ASBS) was first investigated in the present study. The total viable count of control, WC, PS, and PS + WC exceeded the acceptable limit on Days 8, 15, 25, and 30 of storage, respectively. Throughout storage, all three treated samples had a total psychotropic count (TPC) and a Pseudomonas spp. count below the permitted level, with the TPC of control exceeding the limit on Day 20. The PS + WC reduced off-flavour development measured by total volatile base-nitrogen, trimethylamine, and propanal, as well as lipid, protein, and myoglobin oxidations (p < 0.05) compared to PS or control. The PS + WC reduced the discolouration, drip loss, and textural softening of ASBS (p < 0.05), which was comparable to PS and WC (p > 0.05). Thus, conjunction of PS and WC was an effective hurdle technique for extending the shelf-life of ready-to-cook ASBS. This approach was practical and industrially applicable. • PAW soaking plus WPI-ginger extract coating improved shelf-life of sea bass steaks. • With this hurdle, microbial indices were within the acceptable level up to 30 days. • Off-flavour development was reduced and oxidative stability was improved. • Shelf-life of chilled sea bass steaks was extended up to 30 days.

Effects of rearing tank colour on growth indices, blood chemistry, digestive enzymes, expression of stress and growth‐related genes of Asian sea bass juvenile ( Lates calcarifer )

The background colour of the fibreglass tanks attributed to their significant correlation with light intensity and spectrum serves as one of the major factors influencing growth performance and stress levels of cultured fish. Moreover, it plays a key role in the successful production of the cultured species, which is challenging under confinement conditions. On the other hand, Asian sea bass (Lates calcarifer) has received significant attention among researchers due to its high-profit value and growing demand in the global market. Hence, the current study was designed to investigate the effects of different tank background colours (white, red, black and blue) on growth indices, body composition, digestive enzymes, haematological parameters, expression of stress and growth-related factors in L. calcarifer. Therefore, fish (160.90 ± 6.0 g) were distributed into 12 fibreglass tanks (250-L) including four treatments in triplicates and were reared for 6 weeks. According to the present results, the highest specific growth rate was observed in fish raised in red-coloured tank followed by white and black tanks. Maximum weight gain (WG) and high protein efficiency ratio (PER) were observed in fish raised in red-coloured tank followed by white-, black- and blue-coloured tanks, respectively. Modulation of the main digestive enzymes was observed across four treatments indicating different strategies for the utilization of nutrients by fish. Fish from red- and white-coloured tanks showed a lower level of cortisol and higher levels of heat shock protein (HSP70) when compared to the other groups. The present findings indicate that red colour is the most suitable background colour for rearing Asian sea bass juveniles followed by white colour compared with the other ones.

Effect of sodium bicarbonate on textural properties and acceptability of gel from unwashed Asian sea bass mince.

Asian sea bass mince gels having different adjusted moisture/water content (80 and 85%; w/w) were prepared with addition of sodium bicarbonate (SB) at various concentrations (0, 0.05 and 0.1%; w/w). Fish mince gels of 80% water content added with 0.05 and 0.1% SB (G80-0.05 and G80-0.1, respectively) had the highest increase (135-139%) in breaking force (BrF) than the respective control gel (G80) (P < 0.05). For gel with 85% water content, a lower increase (17-28%) in BrF was found with the addition of SB as compared to their corresponding control (G85). Whiteness of all samples was continuously decreased with increasing amount of SB, however the water holding capacity was increased drastically with augmenting levels of SB, regardless of thewater content (P < 0.05). A loss in the elasticity of gel was attained with the addition of SB as indicated by decreasing storage modulus. A finer and more compact network was detected in a gel containing SB, irrespective of water content. Based on sensory scores, gel having 85% water content added with 0.05 and 0.1% SB had similar acceptability to the control gel (G80) containing 80% water content (commercial level). Therefore, SB at the appropriate level could improve the gelling properties with higher water holding ability of the mince gel with high acceptability.

An In-silico Approach for Identifying Phytochemical Inhibitors Against Nervous Necrosis Virus (NNV) in Asian Sea Bass by Targeting Capsid Protein

Nervous necrosis virus (NNV) is a devastating infectious pathogen for fish species with 100% mortality. To date, no specific drugs or vaccines have been developed that can prevent infections in aquaculture caused by NNV. It has been found that the NNV utilizes capsid protein to enter into the host cell in Asian sea bass and cause disease. In this study, we evaluated the inhibitory potential of Allium sativum compounds that have been reported to show antiviral activity against various pathogens. The capsid protein was modeled and the binding affinity of all the compounds was calculated with the docking approach and top 2 (PubChem CID: 122130381 and CID 12303662) inhibitory compounds were selected for further ADMET properties and DFT analysis. Both the geometry optimization and redocking of the two inhibitory compounds (PubChem CID: 122130381 and CID 12303662) showed a strong binding affinity of -8.2 and -8.0 kcal/mol, respectively with the capsid protein. The molecular dynamic simulation approach further validated the capsid protein – CID: 122130381 and capsid protein- CID 12303662 complex stability. In conclusion, this study deduces that these Allium sativum phytochemicals might act as significant inhibitors of the NNV in sea bass, which can be further validated experimentally.

Effect of Asian sea bass bio‐calcium on textural, rheological, sensorial properties and nutritive value of Indian mackerel fish spread at different levels of potato starch

AbstractEffect of potato starch (2%–4%) and Asian sea bass bone bio‐calcium (BC) (0%–10%) on characteristics of Indian mackerel fish spread was investigated. Starch levels had higher impact than bio‐calcium concentration on characteristics of fish spread (P &lt; 0.05). Firmness, consistency and cohesiveness of fish spread were raised with increasing starch and BC levels (P &lt; 0.05). Highest lightness (L*) was found in fish spread added with 2% starch and 10% BC (P &lt; 0.05). Highest a*, b*, C*‐values but lowest hue angle were obtained in fish spread added with 4% starch and 10% BC (P &lt; 0.05). Higher G' and viscosity were observed in sample added with 4% starch when BC was incorporated at higher level. All fish spreads generally showed shear thinning flow behaviour. Higher acceptability was attained for fish spread containing 4% starch and 10% BC without grittiness. This fish spread showed higher ash with lower moisture, protein and lipid contents than those without BC. Calcium solubility of fish spread was augmented after in vitro gastrointestinal tract system when fortified with 10% BC, and higher solubility of calcium was also noticeable, compared to BC itself. Overall high PUFA, acceptable PV and TBARS value were attained for fish spread fortified with 4% starch and 10% BC.

Toward Systematic Breeding of Asian Sea Bass, Lates calcarifer (Bloch, 1790), in Malaysia: Status, Challenges and Prospects for Future Development

Asian sea bass, Lates calcarifer (Bloch, 1790), is one of the most farmed marine fish in Malaysia since the 1970s and is predominantly cultured at present. Although it has been farmed for some time, there is no systematic breeding programme in place. Local hatcheries rely heavily on wild and imported broodstock. However, imported stocks do not guarantee improved quality and even increase the chances of introducing pathogens into the country. Availability of superior breeding stocks, efficient dissemination and control of seed production could greatly assist in increasing Asian sea bass production. This paper presents the status of Asian sea bass production, its culture history in Malaysia and the current broodstock development programme implemented by the Fisheries Research Institute, particularly in the 11th Malaysia Plan from 2015 to 2020. In brief, broodstock from Malaysia, Thailand and Indonesia were used as base population and were mated using full diallel method to produce cohorts. Three pairs of the selected broodstock were used for each cross and spawning performance was evaluated. The growth performances of the first generation (F1) offsprings were assessed in different culture systems. Physico-chemical water quality parameters such as dissolved oxygen, temperature, pH and salinity were maintained at optimal levels during all stages of the experiment. Results indicate that the growth performance of F1 improved by more than 60 % in terms of weight gain compared with the base population. The project demonstrated the benefits of using selective breeding to enhance the production of Asian sea bass.

Beneficial role of polyphenols as feed additives on growth performances, immune response and antioxidant status of Lates Calcarifer (Bloch, 1790) juveniles

Six-week research was conducted to evaluate the effect of dietary supplementation of polyphenols on the performance of Asian sea bass (Lates Calcarifer) juveniles (16.4 ± 0.49 g). The experimental diets included: 0 (control), 0.5, 1.0, 2.5, 5.0 g/kg−1 diet of a mixture of commercially available polyphenol (PMIX), made of chestnut wood extract and olive extract (Silvafeed®TSP, and PhenoFeed®, respectively) The results indicate that 2.5 g/kg diet of PMIX, significantly affected the final weight, final length, specific growth rate, percent weight gain, hepatosomatic index, and condition factor. Daily weight gain was significantly increased in fish fed with 2.5 and 5.0 g/kg diet of PMIX (P < 0.05). There were no significant differences between PMIX treatments and the control group in biochemical blood parameters and body composition (P > 0.05). Analysis of the data shows that mucus lysosomes activity was significantly increased in 0.5, 2.5, and 5.0 g/kg diet of PMIX groups. ACH50 increased in fish fed with 2.5 g/kg diet of PMIX. Total Ig levels in groups of 2.5 and 5.0 g/kg diet of PMIX were better than the control (P < 0.05). Catalase (CAT) increased in fish fed by 5.0 g/kg diet of PMIX compared to control fish (P > 0.05). The glutathione reductase (GR) and glutathione S-transferase (GST) activity in fish fed on 2.5 and 5.0 g/kg diet of PMIX was significantly higher than in the control fish (P < 0.05). There was a significant decrease in Malondialdehyde (MDA) level in the liver of fish fed with 1.0, 2.5, and 5.0 g/kg diet of PMIX. These results indicated that PMIX can be considered as a beneficial dietary supplement for improved growth parameter, mucosal immune response, and liver oxidative status of the Asian sea bass juveniles.

Prevalence and Antimicrobial Resistance of Escherichia coli, Salmonella and Vibrio Derived from Farm-Raised Red Hybrid Tilapia (Oreochromis spp.) and Asian Sea Bass (Lates calcarifer, Bloch 1970) on the West Coast of Peninsular Malaysia.

Antibiotics are widely used in intensive fish farming, which in turn increases the emergence of antimicrobial-resistant (AMR) bacteria in the aquatic environment. The current study investigates the prevalence and determines the antimicrobial susceptibility of E. coli, Salmonella, and Vibrio in farmed fishes on the west coast of Peninsular Malaysia. Over a period of 12 months, 32 aquaculture farms from the Malaysian states of Selangor, Negeri Sembilan, Melaka, and Perak were sampled. Both E. coli and Salmonella were highly resistant to erythromycin, ampicillin, tetracycline, and trimethoprim, while Vibrio was highly resistant to ampicillin and streptomycin. Resistance to the antibiotics listed as the highest priority and critically important for human therapy, such as colistin in E. coli (18.1%) and Salmonella (20%) in fish, is a growing public health concern. The multi-drug resistance (MDR) levels of E. coli and Salmonella in tilapia were 46.5% and 77.8%, respectively. Meanwhile, the MDR levels of E. coli, Salmonella, V. parahaemolyticus, V. vulnificus and V. cholerae in Asian seabass were 34%, 100%, 21.6%, 8.3% and 16.7%, respectively. Our findings provide much-needed information on AMR in aquaculture settings that can be used to tailor better strategies for the use of antibiotics in aquaculture production at the local and regional levels.

Evaluation of the antibacterial activity of Coccinia grandis, against bacteria isolated from chronic suppurative otitis media infection

In vitro antimicrobial activity of betel, Piper betle leaf extract against Vibrio alginolyticus isolated from Asian sea bass, Lates calcariferAhmad Baihaqi Othman, Mohd Zamri Saad , Nik Haiha Nik Yusof, Siti Zahrah Abdullah

Maritime Territorial Disputes and Diplomatic Negotiations in the Northeast Asian Sea: Focusing on the Case of Korea-China Maritime Delimitation Negotiations

Maritime Territorial Disputes and Diplomatic Negotiations in the Northeast Asian Sea: Focusing on the Case of Korea-China Maritime Delimitation Negotiations