Experimental challenge studies in Vietnamese catfish,Pangasianodon hypophthalmus (Sauvage), exposed to Edwardsiella ictaluri and Aeromonas hydrophila     

M Crumlish  P C Thanh  J Koesling  V T Tung  K Gravningen 《Journal of fish diseases》2010,33(9):717-722

The two main diseases in the pangasius catfish industry are bacillary necrosis of Pangasianodon (BNP) and motile aeromonas septicaemia (MAS), where the aetiological agents have been identified as Edwardsiella ictaluri and Aeromonas hydrophila, respectively. In this study, apparently healthy Pangasianodon hypophthalmus were exposed to E. ictaluri, A. hydrophila or both bacterial species by intraperitoneal injection or immersion. There were 20 fish per treatment group, and the bacterial isolates used for the study were recovered from natural infections of BNP or MAS in farmed Vietnamese P. hypophthalmus. The results of the experimental infections mimicked the natural disease outbreaks reported from these pathogens in P. hypophthalmus. Furthermore, it was clearly demonstrated that E. ictaluri was only recovered from the fish exposed to the bacterium and not recovered from the animals receiving A. hydrophila.  相似文献   

Reproductive cycle of yellow croaker <Emphasis Type="Italic">Larimichthys polyactis</Emphasis> in southern waters off Korea     

Han Kyu Lim  Minh Hoang Le  Cheul Min An  Sung Yeon Kim  Mi Seon Park  Young Jin Chang 《Fisheries Science》2010,76(6):971-980

The reproductive cycle and batch fecundity of yellow croaker Larimichthys polyactis were examined in 981 specimens (286 males, 695 females) caught from waters around Mokpo, Busan, and Jeju-do (Korea) between February 2008 and January 2009. Males and females with ripe-stage gonads were collected between April and June, at which time the mean gonadosomatic indices were also high, indicating that the spawning season of yellow croaker around the waters off southern Korea occurs from April to June. Degenerating postovulatory follicles as well as oocytes in the migratory-nucleus stage or hydrated stage were found in ripe-stage gonads, suggesting that this species can spawn repeatedly in a season. Batch fecundity in 45 females with migratory-nucleus or hydrated oocytes ranged from 19,396 to 106,311 eggs in fish varying from 20.0 to 26.7 cm in total length and was found to be positively related to total length and body weight. Our findings should assist in implementing a proper stock assessment of yellow croaker around the waters off Korea.  相似文献   

IncK plasmid-mediated tetracycline resistance in Edwardsiella ictaluri isolates from diseased freshwater catfish in Vietnam     

Tu Thanh Dung  Freddy Haesebrouck  Patrick Sorgeloos  Nguyen Ahn Tuan  Frank Pasmans  Annemieke Smet  Annemie Decostere   《Aquaculture (Amsterdam, Netherlands)》2009,295(3-4):157-159

Eight tetracycline resistant Edwardsiella ictaluri isolates obtained from diseased freshwater catfish (Pangasianodon hypophthalmus) in Vietnam, and showing different resistance phenotypes to other antimicrobial agents, were studied. The tet genes were determined using PCR. Conjugation experiments were performed to assess transferability of the tetracycline resistance determinant and the size and incompatibility group (Inc) of each tet-carrying plasmid were determined. PCR and sequencing were used for characterization of the co-transferred resistance genes. A tetA gene was demonstrated in the E. ictaluri isolates and for all of them, Escherichia coli transconjugants were obtained. All transconjugants contained high-molecular weight tetA-carrying plasmids (~ 140 kb) belonging to the incK group, as was shown with the PCR-based replicon typing method. The strA–strB, dhfr1 and sul 2 genes were detected on the tetA-carrying plasmids of the transconjugants showing resistance to streptomycin, trimethoprim and sulfonamides, respectively. The dhfr1 gene was found to be located in a class 1 integron as determined by PCR and sequencing. Interestingly, the 3′ CS region of class 1 integrons was not detected by PCR. This study shows the presence of incK plasmid-mediated tetracycline resistance among E. ictaluri isolates from diseased freshwater catfish in Vietnam.  相似文献   

Farm types for beef production and their economic success in a mountainous province of northern Vietnam     

Le Thi Thanh Huyen  Pera Herold 《Agricultural Systems》2010,103(3):137-145

The objective of this study was to compare the management and economic success of beef production by three types of farm in northwestern Vietnam. The potential of household farms to supply beef for the market and their competition with large farms were examined.The fieldwork was done in 2007 on 73 farms consisting of 58 small mixed farms (small farms), 10 medium mixed farms (medium farms) and 5 specialised large-scale beef farms (large farms) in Son La province. The three types of farm differed in ethnicity (Thai, H’mong, and Kinh), remoteness (lowland, highland), production objectives (subsistence, market output), degree of specialization (mixed farm, specialised beef farm) and integration of production (single farmers, cooperative). Data on biological productivity, inputs and outputs, and the social contribution of cattle production were collected by household and key person interviews, participatory rural appraisal tools and cattle body measurements. Economic values were derived by assessment of market or replacement costs. Quantitative data analysis was done with linear models (PROC GLM) in the SAS software (version 9.1).Lowland small farms had higher costs for cattle production than the highland farms (0.8 Mill. VND head⁻¹ year⁻¹ compared with 0.02 Mill. VND head⁻¹ year⁻¹, respectively). The large farms had high production costs, with an average of 2.5-3.6 Mill. VND head⁻¹ year⁻¹. Cattle brought high benefits of non-cash values to the household farms. The total revenue from cattle was in the range 4.5-11.5 Mill. VND head⁻¹ year⁻¹, which depended on the use of non-market functions of cattle on the household farm. The value of net benefit/kg live weight (LW) of lowland small farms with an average of 39,000 VND/kg LW was significantly higher than that of the medium and small farms in the highlands (26,000 VND/kg LW). However, the small farms kept fewer cattle than the medium farms (average of 2-4 cattle/farm compared with 9 cattle/farm, respectively) because of forage and labour shortages and have no option to further develop cattle production. Keeping larger numbers of cattle based on available natural pasture brought high benefit from stock value as farm liquidity to only the medium farms. This was the most promising type of farm for future development of beef production, given its actual success and the availability of underutilised resources. Large-scale farms suffered high economic losses of 0.3-1.4 Mill. VND cattle⁻¹ year⁻¹, due to the lack of professional management, high feed costs and low animal performance, and showed no potential for developing cattle production.  相似文献   

‘Blue boats’ and ‘reef robbers’: A new maritime security threat for the Asia Pacific?     

Andrew M. Song  Viet Thang Hoang  Philippa J. Cohen  Transform Aqorau  Tiffany H. Morrison 《Asia Pacific viewpoint》2019,60(3):310-324

Vietnamese ‘blue boats’ – small wooden‐hulled fishing boats – are now entering the territorial waters of Pacific Island countries and illegally catching high‐value species found on remote coastal reefs. Crossing several international boundaries and traversing a distance of over 5000 km, these intrusions have alarmed Oceanic countries, including Australia. Lacking administrative capacity as well as jurisdictional authority to effectively control the vast stretches of island coastlines individually, governments and intergovernmental bodies in the region have called for strengthened coordination of surveillance efforts while also pressuring Vietnam diplomatically. This paper reviews these latest developments and is the first to provide a focused assessment of the issue. Through the lens of Copenhagen School of securitisation theory, we analyse responses of national and regional actors and their portrayal in online media to understand how blue boats are constructed as a security threat within a narrative of maritime, food and human security. Arguably, Australia together with the Forum Fisheries Agency, who advise on the governance of offshore tuna resources, have so far acted most decisively – in a way that might see them extend their strategic role in the region. We propose a comprehensive empirical research agenda to better understand and manage this nascent, flammable and largely unpredictable inter‐regional phenomenon.  相似文献   

Breeding for improved resistance to Edwardsiella ictaluri in striped catfish (Pangasianodon hypophthalmus): Quantitative genetic parameters     

Nguyen Thanh Vu  Nguyen Van Sang  Trinh Quoc Trong  Nguyen Huynh Duy  Nguyen Thi Dang  Nguyen Hong Nguyen 《Journal of fish diseases》2019,42(10):1409-1417

Bacillary necrosis of Pangasius (BNP), caused by Edwardsiella ictaluri, is one of the most devastating diseases in striped catfish farming. To date, quantitative genetic inheritance of BNP resistance is not known in striped catfish Pangasianodon hypophthalmus. The main aim of this study was to estimate genetic parameters for BNP resistance in a breeding population of striped catfish undergoing four generations of selection for high growth. Specifically, the study examined whether BNP resistance is heritable to enable family selection and whether genetic improvement for enhanced BNP resistance may have detrimental effects on growth and survival rate. To test these hypotheses, 720 full‐ and half‐sib families were challenged with E. ictaluri pathogen using injection and cohabitation methods over four years, from 2010 to 2012 and 2015. In total, the data included 398,234 animals in the pedigree, from which 18,849 animals had disease challenge test records and 39,103 siblings had growth performance. Both univariate and bivariate sire–dam linear and threshold mixed models were used to estimate (co)variance components for BNP resistance, survivals and growth traits. The estimates of heritability for the BNP resistance recorded as death or survival were low regardless of models used (0.10–0.16), whereas survival time (days post‐challenge test) showed moderate heritability (0.35). The survival rate during hapa rearing had medium heritability (0.33–0.52). The genetic correlations of BNP resistance with body weight and survival were all positive (0.03–0.53), suggesting that selection of increased BNP resistance may have positive impacts on growth and survival traits, and these traits could be easily improved simultaneously in the selective breeding programme for striped catfish.  相似文献   

The use of machine learning to predict acute hepatopancreatic necrosis disease (AHPND) in shrimp farmed on the east coast of the Mekong Delta of Vietnam     

Khiem  Nguyen Minh  Takahashi  Yuki  Oanh  Dang Thi Hoang  Hai  Tran Ngoc  Yasuma  Hiroki  Kimura  Nobuo 《Fisheries Science》2020,86(4):673-683

Fisheries Science - Predicting the outbreak of disease is essential when managing shrimp farms. Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus is a serious...  相似文献   

Thermal challenge of the Indian shrimp Penaeus indicus     

Tung Hoang  Thi Hong Hanh Bui  Hai Co Ho  Ngoc Phuong Thanh Le 《Aquaculture Research》2020,51(4):1480-1486

This study investigated short‐term effects of increasing water temperature from 27 to 41°C on survival and feed consumption of Penaeus indicus at three different ages: PL₂₅ (postlarvae 25 days old), PL₅₀ and PL₉₀. For each age group, water temperature was maintained at 27°C in the control, but increased to 32, 35, 38 and 41°C at a rate of 1°C every eight hours. The temperature was then kept stable until the end of the 7‐day experiment. Results showed that increasing water temperature affected both survival and feed consumption of the experimental shrimps (p < .01). Survival was highest at 32 and 35°C ranging from 93.8% to 100%, but significantly reduced to 40.0%–81.6% at 38°C. No shrimp survived the 41°C treatment. PL₂₅ were more tolerant to 38–41°C than PL₅₀ and PL₉₀ in terms of survival. Increasing water temperature had no effects on feed consumption of PL₂₅ (p > .05). For PL₅₀ and PL_90, feed consumption significantly increased at 38 and 41°C (p < .01) and was similar within the range of 27–35°C. This study suggests that P. indicus in tropical areas can tolerate water temperatures of at least 35°C and should be considered for farming during the summer time.  相似文献   

The effects of two fish species mullet,Mugil cephalus,and tilapia,Oreochromis niloticus,in polyculture with white shrimp,Litopenaeus vannamei,on system performances: A comparative study     

Manh N. Hoang  Phuoc N. Nguyen  Ana Maria Vital Estrocio Martins Bossier  Peter Bossier 《Aquaculture Research》2020,51(6):2603-2612

A comparative study was carried out to compare the effect of caging mullet and tilapia in a shrimp polyculture system. In six shrimp tanks (three tanks for each fish species), either mullet, Mugil cephalus (CCT‐SM), or tilapia, Oreochromis niloticus (CCT‐ST), was stocked in cages. In three other tanks, mullets were allowed to roam freely in shrimp tanks (D‐SM). White shrimp, Litopenaeus vannamei (0.50 g), was cultured as the predominant species were distributed randomly into nine fibreglass tanks (5 m³) at a density of 300 shrimp/tank, while fish (1.50 g) were stocked at the same density of 10% of the initial total shrimp biomass. The results showed that water quality parameters were not significantly different among treatments (p > .05), except for total suspended solids (TSSs). System performances based on parameters such as total weight gain (2,808.15 g/tank) and nutrient recovery were higher in D‐SM treatment (39.80% for nitrogen and 27.40% for phosphorus) than in CCT‐SM and CCT‐ST treatments (p < .05). These system performance parameters were significantly affected by the mullet‐holding strategy; however, they were not affected by fish species. The addition of mullet or tilapia in shrimp tanks did not affect shrimp growth differentially. Fish growth performances based on parameters such as final weight (98.43 g/fish) and DGR (1.29 g/day) were significantly higher in D‐SM treatment and were significantly different among D‐SM, CCT‐SM and CCT‐ST treatments (p < .05). It is concluded that in shrimp–fish polyculture with a stocking density of fish at 10% of the initial total shrimp biomass, tilapia is more effective than mullet, when caged. However, under free‐roaming conditions, the use of mullet is more effective in terms of system performances relative to a system holding caged tilapia.  相似文献   

Spatial epidemiology of human anthrax in Son La province,Vietnam, 2003–2022     

Tan Luong  Tien Dung Nguyen  Van Truong Lu  Morgan C. Metrailer  Van Khang Pham  Thi Thu Ha Hoang  Thi Mai Hung Tran  Thanh Hai Pham  Thanh Long Pham  Quang Thai Pham  Jason K. Blackburn 《Zoonoses and public health》2024,71(4):392-401

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