Abstract
Rapid growth in production of the farmed Vietnamese whitefish pangasius and its trade with the European Union has provoked criticism of the fish’s environmental, social and safety credentials by actors including WWF and Members of the European Parliament and associated negative media coverage. This paper reviews the range of claims communicated about pangasius (identified as a form of mass mediated risk governance), in light of scientific evidence and analysis of data from the EU’s Rapid Alert System for Food and Feeds food safety notification system for imported seafood. This analysis shows pangasius to be generally safe, environmentally benign and beneficial for actors along the international value chains that characterise the trade. The case is made that increasingly politicised debates in Europe around risk and uncertainty are potentially counterproductive for EU seafood security and European aquaculture industry, and that the trade in pangasius can contribute to sustainable seafood consumption in a number of ways. Transparent evidence-based assessment and systems for communicating complex issues of risk for products such as pangasius are required in order to support continuance of fair and mutually beneficial trade.
David C. Little, Simon R. Bush, Ben Belton, Nguyen Thanh Phuong, James A. Young, Francis J. Murray. Marine Policy, Volume 36, Issue 3, May 2012, Pages 738–745.
Article available at: http://www.sciencedirect.com/science/article/pii/S0308597X11001564
Abstract
In this study we investigated nitrite (NO2−) effects in striped catfish, a facultative air-breather. Fish were exposed to 0, 0.4, and 0.9 mM nitrite for 0, 1, 2, 4, and 7 days, and levels of functional haemoglobin, methaemoglobin (metHb) and nitrosyl haemoglobin (HbNO) were assessed using spectral deconvolution. Plasma concentrations of nitrite, nitrate, chloride, potassium, and sodium were also measured. Partitioning of oxygen consumption was determined to reveal whether elevated metHb (causing functional hypoxia) induced air-breathing. The effects of nitrite on maximum oxygen uptake (MO2max) and critical swimming speed (Ucrit) were also assessed. Striped catfish was highly tolerant to nitrite exposure, as reflected by a 96 h LC50 of 1.65 mM and a moderate nitrite uptake into the blood. Plasma levels of nitrite reached a maximum after 1 day of exposure, and then decreased, never exceeding ambient levels. MetHb, HbNO and nitrate (a nitrite detoxification product) also peaked after 1 day and then decreased. Only high levels of nitrite and metHb caused reductions in MO2max and Ucrit. The response of striped catfish contrasts with that seen in most other fish species and discloses efficient mechanisms of combating nitrite threats. Furthermore, even though striped catfish is an efficient air-breather, this species has the ability to sustain aerobic scope and swimming performance without air-breathing, even when faced with nitrite-induced reductions in blood oxygen carrying capacity. Our study is the first to confirm that high levels of nitrite and metHb reduce MO2max and thereby aerobic scope, while more moderate elevations fail to do so. Further studies are needed to elucidate the mechanisms underlying the low nitrite accumulation in striped catfish.
Sjannie Lefevre, Frank B. Jensen, Do T.T. Huong, Tobias Wang, Nguyen T. Phuong, Mark Bayley. Aquatic Toxicology (2011) 104 (2011) 86–93.
Article available at http://www.sciencedirect.com/science/article/pii/S0166445X11000981
Abstract
The striped catfish (Pangasianodon hypophthalmus) (Sauvage), also referred to as tra catfish or sutchi catfish, farming sector is an icon of aquaculture development in Vietnam and globally. Over a decade it has developed from a humble backyard operation to one that currently accounts for the production of over one million tonnes, employing over 180 000 rural poor, and generating an export income exceeding US$ 1.4 billion (2010). It accounts for the highest average production, ranging from 200 to 400 t ha−1 crop, ever recorded for the primary production sector. The system is integrated and incorporates seed production, fry to fingerling rearing and grow-out, and is concentrated in a few provinces in the Mekong Delta (8°33′–10°55′N, 104°30′–106°50′E), along two branches of the Mekong River. In essence, perhaps, the initial trade restrictions on catfish exports to the USA provided the impetus and then the associated developments from 2002 to 2005 of the sector to a great extent in seeking new markets. The explosion of tra catfish farming has resulted in many competitive sectors challenging this ‘tra catfish’ invasion into a globalized market. These confrontations still exist with many instances of attempts to discredit the sector and discourage international consumers. However, the Vietnamese catfish sector is resilient and has managed to withstand such pressures and continues to thrive. This paper reviews the development of catfish farming in the Mekong Delta, its current status and what is required to sustain it as a major food source and livelihood provider.
Sena S. De Silva and Nguyen T. Phuong. Reviews in Aquaculture. Volume 3, Issue 2, pages 45–73, June 2011.
Article available at http://onlinelibrary.wiley.com/doi/10.1111/j.1753-5131.2011.01046.x/abstract
Abstract
Production management of intensive prawn farming strongly differs between dry and wet season in terms of availability and quality of prawn seeds and water quality. Secondary data implied that prawn seed batches from the market had a total pathogen infection rate of 53%, predominantly caused by 37% white spot syndrome virus (WSSV), 19% monodon baculovirus (MBV) and 4% yellow head virus (YHV). Pathogen-free seed batches averaged to 52% during the dry season compared to the wet season (42%). Survey revealed average stocking density of 17 PL m−2 with a survival rate of 55%, a crop yield of 2,470 kg ha−1 crop−1 and a net income of 6,768 USD ha−1 crop−1. Average production cost amounted to 3.4 USD kg−1, and feed cost accounted for 58% of the production cost. Technical efficiency with respect to prawn yield and survival rate was higher during the dry season than the wet season. The probability of yield loss was 15.6 times higher in the wet than in the dry season. A positive net income can be generated for farms operating in the dry season using new ponds and performing pathogen laboratory tests on prawn seeds before stocking.
Vu Nam Son, Nguyen Thanh Phuong, Tran Ngoc Hai and Amararatne Yakupitiyage. Aquacultture International (2011) 19: 555-566.
Article available at http://www.springerlink.com/content/b654q33816850u22/
Abstract
Aquaculture of catfish, Pangasianodon hypophthalmus (Sauvage), locally known as “ca tra”, and commonly referred to as striped catfish, river catfish and sutchi catfish, in Vietnam, having recorded a production of 683,000 tonnes in 2007, valued at about 645 million US$ is one of the largest single species based farming system, restricted to a small geographical area, in the world. The product is almost totally exported to over 100 countries as frozen fillets, as an acceptable alternative to white fish. Catfish is farmed mostly in earthen ponds, up to 4 m deep, in nine provinces in the Mekong Delta in South Vietnam. The results of the grow-out system of catfish farming in the Mekong Delta from a survey of 89 farms are presented. The farm size ranged from 0.2 to 30 ha with a mean of 4.09 ha. The frequency distribution of the yield in tonne/ha/crop and tonne/ML/crop corresponded to a normal distribution curve, where 75% of the farms yielded 300 tonnes/ha/crop or more. It was found that the yield per crop was significantly correlated (p < 0.05) to stocking density, pond depth and volume but not to pond surface area. Yields per crop was significantly different (p < 0.05) between upper and lower provinces of the Mekong Delta and water source (river versus channels), amongst others. It was evident that diseases and/or symptoms were observed to occur mostly in accordance with the onset of rains. In this paper the history of the catfish farming in the Mekong Delta is briefly traced, and current harvesting and marketing procedures as well as pertinent social elements of the farming community are dealt with.
Lam T. Phan, Tam M. Bui, Thuy T.T. Nguyen, Geoff J. Gooley, Brett A. Ingram, Hao V. Nguyen, Phuong T. Nguyen and Sena S. De Silva. Aquaculture 296 (2009) 227–236
Article available at http://www.sciencedirect.com/science/article/pii/S0044848609007066
Abstract
Hatchlings to fry, and fry to fingerling rearing of the striped catfish (Pangasianodon hypophthalmus) sectors of the Mekong Delta (8°33’- 10°55′N; 104°30’-106°50′E), Vietnam, a practice that has witnessed an explosive growth (1,094,879 tonnes, in 2008), in an area of approximately 7,000ha, and the produce exported to over 100 countries, is presented. The findings are based on a survey of 45 hatcheries and 47 nursery farms located in three provinces (Dong Thap, An Giang and Can Tho) where these activities are predominant. Hatchery and nursery farm size ranged from 0.2-15ha (2.5±0.5ha), with 0.05-10ha (1.59±0.3ha), and from 0.09-11ha (mean 1.9±0.4ha), with 0.01-8ha (1.36±0.28ha) under water, respectively. Hatcheries maintained 350 to 29,200 (8,042±805) fish, of which 240-11,300 (4,100±454) are considered as broodstock, the rest being potential broodstock. The mean weight of male and female broodstock ranged from 0.5-8kg and 0.5-12kg, respectively, maintained at a ratio of 0.05-1.0 (mean 0.34±0.03). Fish spawned were at least 1.75kg (female) and 1.5kg (males), and induced spawned by injection with HCG. Females received four or five doses at a time (averages 542, 597, 893 and 3,442IU/kg or 500, 500, 500, 1500 and 3000IU/kg; injected at 0, 23, 46, 56 and 66hrs). Ovulation occurred 5-11hours after the last injection (at 28-29°C). The relationship of relative fecundity and larvae per kg to body weight are: Eggs/ kg (mil.)=0.151 – 0.015 x female wt (kg) (P=0.006, Adj. R2=0.179), Larvae/ kg (mil.)=0.108 – 0.012 x female wt (kg) (P=0.006, Adj. R2=0.182)
Tam M. Bui, Lam T. Phan, Brett A. Ingram, Thuy T.T. Nguyen, Geoff J. Gooley, Hao V. Nguyen, Phuong T. Nguyen, and Sena S. De Silva. Aquaculture 306 (2010) 92–100.
Article available at http://journals1.scholarsportal.info/details.xqy?uri=/00448486/v306i1-4/92_spposcitmdrv.xml