Ministry of Agriculture and Rural Development COLLABORATION FOR AGRICULTURE AND RURAL DEVELOPMENT (CARD) 002/05 VIE Technical and economic feasibility of applying the Better Management Practices (BMP) to household aquaculture in Vietnam MS 8: Technical Report Environmental and Economic Evaluation of Better Management Practices for Shrimp Culture in Vietnam Nguyen Xuan Suc1, Dinh Van Thanh1, Bui Kien Cuong1, Virginia Mosk2 and Elizabeth Petersen2 § Research Institute for Aquaculture No (RIA1), Tu Son, Bac Ninh The University of Western Australia, 35 Stirling Hwy, NEDLANDS WA 6907 Corresponding Author: Liz.Petersen@tpg.com.au, Ph/Fax: +61 9332 8310 - 2008 - Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Acknowledgements The authors would like to sincerely thank the Collaboration for Agriculture and Rural Development (CARD) Programme for funding this research We would also like to thank the following institutions for their support: • The Research Institute for Aquaculture Number in Vietnam, • The University of Western Australia, • The Center for Fisheries Extension in Ha Tinh, Nghe An, and Thua Thien-Hue, • Vietnam’s National Fisheries Quality Assurance and Veterinary Directorate (NAVIQAVED), and • The nine farming households for participating in the trial: o Phan Ngan, o Hau Van Anh, o Tran Dinh Van, o Cao Xuan Hoa, o Le Van Tuan, o Dinh Van Dung, o Nguyen Hong Quyen, o Nguyen Ngoc Hanh, and o Hoang Xuan Kien Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Executive Summary The aim of the report is to provide an initial investigation into whether Better Management Practices (BMPs) can be adopted by Vietnamese shrimp farmers to reduce the environmental and food safety risks of shrimp production, while ensuring the farms remain economically viable It includes analysis of data from in-field measurements and laboratory analysis of key environmental quality parameters at different locations within shrimp farming systems that implemented BMPs, including water in inlet canals before it enters cultivation ponds, water within the cultivation ponds themselves, and water in outlet canals once it has exited the pond The same in-field measurements and laboratory analysis is conducted for shrimp ponds of nine farming households implementing BMPs (three each in Nghe An, Ha Tinh and Thua Thien-Hue) Chemical and microbial analysis is also conducted on shrimp produced in these nine households, and the economic viability of their operations is assessed While trials need to be conducted on a larger number of farms over a longer time period for the findings to be presented with confidence, initial results in this report suggest that implementation of BMPs are generally effective at controlling environmental water quality, and chemical and microbial outbreaks Moreover, the profitability of farms using these practices are just as cost-effective as farms that not use BMPs (the benefit cost ratio of BMP and non-BMP farms are similar) Hence, widespread adoption of these practices in Vietnam is not likely to have a detrimental impact on profitability of farming enterprises Rather, it is likely to have a positive impact if export markets can be ensured or possibly expanded with product certification Specific key findings Analysis of environmental water sampling showed that, on average, a number of parameters were within recommended limits for maximising shrimp production, including: salinity and water temperature (although significant variation outside recommended limits was reported through time for these two parameters), pH, ammonia, alkalinity, nitrogen dioxide and hydrogen sulphide, Transparency readings were found to be slightly problematic being mostly above the optimal range which showed a difficulty in establishing good phytoplankton blooms Temperature was sometimes found to be lower than recommended levels for optimal production, The one problematic environmental parameter was dissolved oxygen – with levels being consistently below recommended levels for maximised production, especially in the morning Moreover, low dissolved oxygen levels in output channels have the potential to be hazardous to significant varieties of fish fauna Pond aeration prior to discharge is likely to negate these impacts, although the cost impacts to the shrimp enterprise needs to be assessed, Chemical and microbial analysis found no or negligible levels of chemicals or microbes harmful to shrimp (for production or food safety) or the environment, Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Total costs of half-hectare shrimp operations is approximately 55 million VND (approximately USD3,400 at the time of writing) These costs are dominated by feeding (51%) There is significant variation in costs across farms, The average production is just over tonne/half-hectare operation, valued at 76 million VND (approximately USD4,700 at the time of writing) This is also very variable across shrimp operations, The average price received for the shrimp was 73,000VND per shrimp, although higher prices were received for larger shrimp compared with the small shrimp (by weight), Profit was approximately 21 million VND (approximately USD1,300 at the time of writing), compared with million VND for non-BMP farmers The average Benefit Cost Ratio was approximately 1.3, on par with non-BMP farmers This suggests that the study farms invested significantly more funds into their operations, than the average nonBMP farmer, If environmental water quality is contained within recommended limits, and chemical and microbial outbreaks are avoided, then the major determinant of profit was feeding The most cost-effective farms were those that invested heavily in feeding the shrimp 10 There are significant opportunities for increased capitalisation of shrimp enterprises Significant growth in Vietnam’s shrimp aquaculture industry has the potential to be sustained in the medium-term Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Table of Contents Acknowledgements Executive Summary Introduction Methodology Environmental Quality of Shrimp Aquaculture Systems 10 3.1 Transparency 10 3.2 Salinity 11 3.3 pH 12 3.4 Dissolved oxygen (DO) 12 3.5 Water temperature 13 3.6 Ammonia (NH3) 14 3.7 Alkalinity 15 3.8 Nitrite 15 3.9 Sulphides 16 3.10 Key findings 17 Household Shrimp Production 18 4.1 4.2 4.3 4.4 4.5 4.6 General information on household operations 18 Environmental water quality data 19 Shrimp produt quality analysis (chemical and microbial) 22 Costs of production 23 Production volume and value 27 Profit and Benefit Cost Ratio 29 Discussion and Conclusions 31 5.1 Environmental water quality parameters 31 5.2 Shrimp production and profitability 32 5.3 Summary comments 33 Bibliography 34 Appendix 1: Better Management Practices 35 Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Introduction Household shrimp production is the predominant form of coastal aquaculture in Vietnam In 2006, approximately 459,000 tonnes of shrimp was produced comprising 12% of total fisheries production in Vietnam (USDAFAS 2007) Approximately 34% of shrimp production (158,000 tonnes) was exported at a value of USD1.46billion Shrimp production is increasing, with an average of 13% growth experienced each year from 2000 to 2006 (USDAFAS 2007) Prices have remained steady such that the growth in the value of shrimp production is similar to the growth in volume Approximately 70% of shrimp production (by volume) is produced through aquaculture operations, which comprises approximately 24% of total aquaculture production by volume but 71% by value (Fistenet 2007) Aquaculture production of shrimp experienced an average of 26% growth between 2001 and 2006, compared with 2% growth in the wild-caught sector In recent years, residues and contaminants have been detected in exported shrimp, with devastating results in markets In 2003, five consignments from Thua Thien-Hue (TT-Hue) province to the European Union were destroyed or returned because of the presence of residues, and a far larger quantity from all north central provinces were similarly treated in 2004 Low standards of education, limited farm capital and minimal opportunities for capacity-building amongst households have resulted in inappropriate farm practices, which have caused degradation of the environment, declines in water quality, loss of farm resources and disease outbreaks As a consequence, the livelihood of many of these farmers is threatened The loss of production, negative environmental and socio-economic impacts, and food safety concerns have provided impetus for the development and extension of better management practises (BMP) for household shrimp farms BMPs have been used in many countries to implement the more general principles of responsible shrimp farming (FAO 2005) They can be defined as farm and local-level practices aimed at enhancing efficiency, productivity, mitigating negative environmental and socio-economic impacts, and suppling products that meet requirements of food safety BMPs are voluntary and are becoming widely used as an important strategy to enhance the marketability of aquaculture product A number of projects have contributed to the development of practical BMPs for shrimp farming in Vietnam (e.g a DANIDA-funded (Danish International Development Agency) SUMA/NACA project (Support to Brackish Water and Marine Aquaculture/Network of Aquaculture Centre in Asia-Pacific), and a NAFIQAVED (National Fisheries Quality Assurance and Veterinary Directorate) pilot project - see Appendix for the list of BMP protocols) These projects have proposed specific BMPs and have conducted some small-scale testing of these BMPs Their findings have not yet been widely disseminated among producers and BMP implementation is still limited This is due to a number of financial, social, technical and economic feasibility constraints Small-scale household shrimp farms are extremely diverse and fragmented, and their capacities to adopt BMP are hampered by lack of awareness, capital constraints and lack of perceived incentive The benefits of applying BMP to Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam household farms remain to be fully investigated However, experience in Thailand, India and Bangladesh has shown that small-scale farmers who applied BMPs made gains in efficiency, productivity and quality (SUMA, 2004) This report is one output of a project jointly funded by the Australian Agency for International Development (AusAID) and the Vietnam Ministry of Agriculture and Rural Development (MARD) through the Collaboration for Agriculture and Rural Development Programme (CARD) The aim of the report is to provide an initial investigation into whether BMPs can be adopted by Vietnamese shrimp farmers to reduce the environmental and food safety risks of shrimp production, while ensuring the farms remain economically viable It presents the results of environmental and economic evaluation of BMP trials in three provinces of Vietnam (Ha Tinh, TT-Hue and Nghe An) The evaluation includes analysis of water quality as it enters and leaves shrimp ponds, product quality data, and economic assessment of household incomes for those participating in the BMP trials The report proceeds with a methodology (Section 2), an analysis of environmental quality parameters of shrimp aquaculture systems (including the potential impact of shrimp production on food safety and the environment) (Section 3), and an analysis of household shrimp production (including food safety, production and profitability aspects of households implementing BMPs) (Section 4) The report finishes with a discussion and conclusion regarding the initial assessment of the cost-effectiveness of BMP adoption in reducing environmental and food safety risks (Section 5) Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Methodology Data collection was conducted over a five month period, March to July 2007, in three provinces; Ha Tinh, Nghe An, and Thua Thien-Hue (TT-Hue) (see Figure 1) Figure 1: Vietnamese provincial map indicating the location of the three project provinces Data was collected by three sources: Extension officers These data include in-field measurements and laboratory analysis of key environmental quality parameters at different locations within the project site Data is presented for inlets (water in inlet canals before it enters the ponds), outlets (water in outlet canals once it has exited the pond), and within the ponds themselves Readers are referred to Ha and Suc (2007) for more information on project sampling sites Farmer households These data include in-field measurements of key environmental quality, production and economic parameters collected by nine different shrimp farmers within the project site NAVIQAVED officers (Vietnam’s National Fisheries Quality Assurance and Veterinary Directorate) NAVIQAVED controls food safety and veterinary services for seafood products in Vietnam They provide chemical and microbiological analyses of shrimp produced by the nine farmer households during the trial period Research Institute for Aquaculture No & The University of West Australia Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam In-field measurements included: • pH: measured with a portable pH meter (YSI 52) • Salinity: use of refractometer (Spec T2000) • Dissolved Oxygen (DO): measured with an oxygen meter (YSI 52) • Temperature (oC): measured with a digital thermometer (Thermo 100) • Transparency (cm): measured with Secchi disk The running river water was used as a supply source for in-field laboratory analysis Samples were collected using a peristaltic pump with two heads, were kept cool with ice, and then analyzed immediately upon reaching the laboratory All analysis followed standard methods (Alpha 1998), and included: • Alkalinity (mg/l), • Ammonia (mg/l), • Nitrite (mg/l), and • Sulphide (mg/l) In-field measurements and laboratory analyses were conducted by Extension Officers and the nine farming households (with assistance from the Vietnamese research team) The nine farming households also completed a shrimp culture diary to collate production and economic information The Vietnamese project team took the shrimp product samples from the nine households to Vietnam's NAVIQAVED for shrimp product quality analysis (including chemical and microbial analysis) The Vietnamese and Australian partners (Research Institute for Aquaculture No.1 and the University of Western Australia) collaborated in the data analysis and report writing Three Vietnamese project partners visited Perth in December 2007 to collaborate with the Australian project partners to conduct initial data analysis, discussion and planning The analysis and report was finalised through email contact Project team The Vietnam-based project team comprised: Mr Nguyen Xuan Suc, Project Leader, Dr Dinh Van Thanh, and Mr Bui Kien Cuong The Australian-based project team comprised: Dr Elizabeth Petersen – Adjunct Senior Lecturer, the University of Western Australia, and Applied Economist, Advanced Choice Economics Pty Ltd, Ms Virginia Mosk, MSc – Technical Aquaculture Consultant to The University of Western Australia, and Associate Professor Steven Schilizzi – The University of Western Australia Research Institute for Aquaculture No & The University of West Australia Environmental Quality of Shrimp Aquaculture Systems This section presents data collected by Extension Officers on nine environmental water quality parameters, which was taken at approximately two week intervals over a four month period from March/April – June/July 2007 (the exact time period differs across provinces) These tests were done at three demonstration farms Testing was conducted on water within ponds, as well as on water before it enters the ponds (inlets) and after it has exited the ponds (outlets) Key findings are presented at the end of this section (Sub-section 3.10) 3.1 Transparency It is recommended that transparency (Secchi disc visibility) remain between 25 and 40cm for maximum production (Boyd 1990) If transparency is less than 25cm and the pond is too turbid with phytoplankton, this may create problems with dissolved oxygen If the reading is greater than 40cm then the phytoplankton is too scarce Transparency readings were found to be above the maximum level at the start of the production period in ponds of all three provinces, decreasing to within recommended levels half way through the season in Ha Tinh and Nghe An (Figure 2) While transparency readings were higher than recommended in the inlets and outlets of all provinces (with the exception of the outlets in TT-Hue), transparency is considered to be an indication of pond condition and phytoplankton density, and is therefore less important in the inlet and outlet channels Transparency levels in the inlet and outlet are unlikely to have an impact on the environment, or affect food safety, as it is purely an optimal range for the best growth of the shrimp Plankton blooms favour greater shrimp production by stimulating the growth of shrimp food organisms and it also limits the visibility of the shrimp from predatory birds, thus reducing stress to the target species allowing them to roam and feed, and develop more quickly 10 Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam 4.6 Profit and Benefit Cost Ratio Figure 12 presents profit and benefit cost ratio per half-hectare for each shrimp producing household On average, these operations are profitable, with average profit being 21 million VND/half-ha (approximately USD1,300 at current exchange rates) This is higher than the average non-BMP shrimp producer where profit is approximately million VND/half-ha However, two of the operations made a net loss The variability of profit is high (the coefficient of variation is 144%), with profit ranging from -26 million to 49 million VND/half-hectare The average benefit cost ratio is 1.3, indicating that on average, for every VND spent, the farmer will receive 1.3 VND in return (this is on par with the benefit cost ratio of non-BMP farmers) However, this too varies significantly across enterprises, from 0.4 to 1.8 2.0 80.0 1.8 1.6 60.0 40.0 1.4 1.2 20.0 1.0 0.8 0.0 -20.0 0.6 0.4 Benefit Cost Ratio Profit (million VND/half-ha) 100.0 0.2 0.0 -40.0 Household number Profit BCR Figure 12: Profit and benefit cost ratio per household While a larger number of shrimp farms would be needed to determine the characteristics that lead to profitable shrimp production, analysis of the data presented in this report shows that those farmers who used relatively high quantities of feed produced significantly higher production, both in terms of weight and value (see Figure 13).2 They produced significantly higher number of relatively large sized shrimp Profitability does not seem to be related to other factors such as size of pond, environmental water quality (although, all ponds exhibited quality data generally within the optimal range for Vietnam), number of seed purchased, the number of quality checks made on the seed, chemical use, water treatment use, or fertiliser use The most profitable of the nine farmers had relatively high costs, but these costs were rewarded with very high returns The correlation coefficient (an indicator of the strength and direction of a linear relationship between two random variables) between profitability and feed costs is equal to 0.88 The correlation coefficient between profitability and shrimp of size 35-45 shrimp/kg, 45-55 shrimp/kg and > 55 shrimp/kg is 0.95, 0.41 and 0.55, respectively There is no strong relationship between profitability and other types of costs Research Institute for Aquaculture No & The University of West Australia 29 Profit (million VND/half-ha) Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam -40.0 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 -20.0 0.0 20.0 40.0 60.0 80.0 100.0 Feed costs (million VND/half-ha) Figure 13: The relationship between profit and feed costs Research Institute for Aquaculture No & The University of West Australia 30 Discussion and Conclusions 5.1 Environmental water quality parameters Both the Household and Extension officers’ environmental data reflected ongoing problems with transparency with readings being over the acceptable maximum level of 40cm, some also fell below the minimum of 25cm Comparisons of these data with the baseline data for the project shows similar results for sites at Nghe An and Ha Tinh (Ha and Suc 2007) Baseline data for Thua Thien Hue reflected optimal transparencies within the ideal range However, the transparency readings deteriorated during the BMP trial in this province Turbidity caused by plankton blooms is generally desirable in fish and shrimp ponds (Boyd 1990) It reduces the likelihood of troublesome underwater weeds as it inhibits sunlight penetration and their development via photosynthesis Plankton blooms favour greater shrimp production by stimulating the growth of shrimp food organisms It also limits the visibility of the shrimp from predatory birds, thus reducing stress to the target species allowing them to roam and feed If transparency (Secchi disc visibility) is less than 25cm and pond is too turbid with phytoplankton this may create problems with dissolved oxygen If the reading is greater than 40cm then the phytoplankton is too scarce It is desirable that plankton blooms are encouraged more strongly with aeration and fertilisation (if too little is being used), to create a consistent bloom in all ponds The drop in salinity, water temperature and pH, and the rise in alkalinity at the midseason point in these ponds would reduce turbidity of the water thus reflecting declined transparency readings Salinity from original baseline data fell within the suitable range of 15–25%o Household and extension officer’s results correlated with all ponds beginning in the optimal range, ponds in Nghe An and Ha Tinh rising steadily towards the end of the season and finishing over the optimal range at 27%o TT-Hue reflected an aberration with a sharp drop mid season to below the optimal range then rising gradually As previously noted in the household data comments, this was due to heavy rainfall as it also affected water temperature, pH, alkalinity and ammonia contemporaneously The individual household data comments from the farmers indicate that heavy rain occurred a number of times in the TT-Hue district as well as Ha Tinh Even though Penaeus monodon is chosen for this area due to its tolerance for salinity fluctuations, if the water is changed more than 10%o every few minutes or hours, shrimp may be unable to compensate Tangko & Wardoyo (1985) found that survival of Penaeus monodon decreased from 82.2% to 56.7% when salinity was lowered at 2.5%o/hr compared with 10.0%o/hr Fluctuations in salinity are especially critical when shrimp moult Low dissolved oxygen was problematic in the early mornings for most ponds Some ponds suffered low dissolved oxygen both in morning and afternoon, with corresponding poor health, growth rates and increased shrimp mortality Interestingly, the baseline dissolved oxygen levels for all areas were within the optimum range (Ha and Suc 2007), therefore the natural environment is not the concern The oxygen levels during the growout phase needs attention and swift 31 Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam response is necessary when farmers see this deterioration There are several ramifications of low dissolved oxygen; firstly fry survival is reduced, then in adults the growth rate, weight gain and feed consumption decline with decreasing dissolved oxygen This increases food conversion ratios, which greatly impact water quality as feed remains unconsumed and falls to the bottom creating areas of low dissolved oxygen Continued exposure to low dissolved oxygen also is considered to be a precursor to bacterial infection (Snieszko 1973; Plumb et al 1976) Homemade food, whilst it is being phased out in the three research areas, can add to the biological oxygen demand as it rapidly disperses and settles on the bottom of the ponds Low dissolved oxygen levels are easily alleviated with aeration; hence it is highly recommended that effective aeration be put in place for future seasons and used at the applicable times of the day Stagnant areas of the ponds, which were not aerated and circulated properly, will affect an overall reduction of oxygen in the system It is imperative that aerators are placed at correct positions to gain the maximum circulation Shrimp being poikilothermic or “cold-blooded” means that their body temperature is roughly the same as the temperature of the surrounding water So shrimp body temperature changes frequently and the rates of biochemical processes are temperature dependent Oxygen consumption increases with temperature until it reaches a maximum where a lethal temperature is finally reached All areas had temperature fluctuations throughout the season, although it stayed predominantly within the optimum range for this species There was a rapid drop in temperature in the Extension officers’ data in mid April for TT-Hue and early May for Nghe An As it was only 2-3 degrees, it is unlikely that the shrimp would have suffered shock, although a larger fluctuation would Alkalinity was generally within the optimal range for all ponds Whilst the baseline survey at the TT-Hue site was the only area to have excessive alkalinity readings, the post cultivation period showed that the TT-Hue farmers had alkalinity under control; hence the conditions were better than when they started Ammonia, nitrate and sulphide levels stayed within optimal levels for both sets of data, hence would have no impact on the growth of the shrimp 5.2 Shrimp production and profitability The average feed conversion ratio, growth rate, survival rate and size at harvest for the nine ponds was 1.6, 0.16 g/shrimp/day, 69% and 50 shrimp/kg, respectively There was little variation in these findings between ponds Despite differences early in the production season, shrimp length and weight were very similar at the time of harvest The average production for a half-hectare shrimp farm is just over tonne, although this varies significantly across households The average value of production per halfhectare is approximately 76 million VND, although this also varies significantly across households (ranging from 10 to 217 million VND/half-ha) The average price received for the shrimp was approximately 73,000VND/kg, although relatively larger shrimp received relatively higher prices Total costs for a half-hectare operation is approximately 46.6 million VND per year This equates to a little over AUD3,000 at the current exchange rate Costs are Research Institute for Aquaculture No & The University of West Australia 32 Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam dominated by feeding (51%) followed by chemicals (11%) and labour (11%) The variability of costs was significant across households The average profit per half-hectare pond was approximately 21 million VND (approximately USD1,300 at current exchange rates) This is significantly higher than the average non-BMP shrimp producer where profit is approximately million VND/half-ha The average benefit cost ratio is 1.3, indicating that on average, for every VND spent, the farmer will receive 1.3 VND in return (this is on par with the benefit cost ratio of non-BMP farmers) This provides evidence that farmers that use BMPs in Vietnam can be profitable, and that BMPs may have the impact of increasing profitability However, it should be noted that the variability of profitability was significant, and two of the nine operations made a net loss A larger study would be needed to determine the characteristics leading to increased profitability of shrimp production, however this analysis shows that in the absence of issues associated with chemical and microbial outbreaks, and ensuring that environmental water parameters remain within desirable limits, farmers who used relatively high quantities of feed produced significantly higher quantities of shrimp, leading to significant higher profitability There was no significant correlation between profitability and any other cost source The most profitable of the nine farmers had relatively high feed costs, but these costs were rewarded with very high returns There are significant opportunities for increased capitalisation of shrimp enterprises Significant growth in Vietnam’s shrimp aquaculture industry has the potential to be sustained in the medium-term 5.3 Summary comments The farmers who took part in the Better Management Practice trial were successful in understanding environmental water quality parameters and their effects long-term to their own operations, as well as the surrounding environment They also have a better understanding of controlling chemical and microbial outbreaks Moreover, the profitability of farms using these practices were just as cost-effective as farms that not use Better Management Practices (the benefit cost ratio of BMP and non-BMP farmers are similar) Hence, widespread adoption of these practices in Vietnam is not likely to have a detrimental impact on profitability of farming enterprises Rather, it is likely to have a positive impact if export markets can be ensured or possibly expanded with certification that exported product does not contain food safety concerns, and has been produced with minimal environmental impact Research Institute for Aquaculture No & The University of West Australia 33 Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam Bibliography Boyd C E (1990) Water Quality in Ponds for Aquaculture Burmingham Publishing Company, Burmingham, Alabama Chin T S & Chen J C (1987) Acute Toxicity of Ammonia to Larvae of the Tiger Prawn, Penaeus monodon Aquaculture, 66: 247-253 Ellis, M M (1937) Detection and Measurement of Stream Pollution USA Bureau of Fish., Bulletin 22: 367-437 Fistenet (2007) Fisheries scientific-technical economic Information Centre, Vietnam (www.fistenet.gov.vn) information Fisheries Food and Agriculture Organization (FAO) (2005) Code of Conduct for Responsible Fisheries FAO, Rome Ha, M.V and Suc, N.X (2007) Technical and Economic Feasibility of Applying the Better Management Practices (BMP) to Household Aquaculture in Vietnam MS3 Initial Environmental Assessment Report Research Institute for Aquaculture Number Hanson L.A & Grizzle J.M (1985) Nitrite-induced predisposition of channel catfish to bacterial diseases Prog Fish-Culture, 47: 98-101 Plumb J.A., Grizzle J.M & Defigueiredo, J (1976) Necrosis and bacterial infection in channel catfish (Ictalurus punctatus) following hypoxia Journal Wildlife Diseases, 12: 247-253 Schwedler T.E, Tucker C.S & Baleau M.H (1985) Non-infectious diseases, p 497541 In: C S Tucker (ed.), Channel Catfish Culture Developments in Aquaculture and Fisheries Science, Vol 15, Elsevier, New York Snieszko S.F (1973) Recent advances of scientific knowledge and developments pertaining to diseases in fishes Adv Vet Sci Comp Med, 17: 291-314 Support to Marine and Brackish Aquaculture (SUMA) (2004) Proceedings of Workshop on Code of Conduct for Responsible Fisheries and Code of Practise/Good Aquaculture Practice in Vietnam Hanoi, 5-6 August, 2004 SUMA publication, Hanoi Thanh, D.V., Suc, N.X, Petersen, E.H., McCartney, A., and Schilizzi, S (2007) Economic and Technical Evaluation of Shrimp Culture Management Practices in Northern Vietnam Collaboration for Agriculture and Rural Development 002/05/VIE Working Paper United States Department of Agriculture Foreign Agricultural Service (USDAFAS) (2007) Vietnam Fishery Products Annual Report 2007 Global Agriculture Information Network (GAIN) Report Number VM7043, June 2007 Research Institute for Aquaculture No & The University of West Australia 34 Appendix 1: Better Management Practices I POND PREPARATION 1.1 Pond condition The area of semi-intensive pond should be from 0.5-0.7 ha, with well-constructed and separated inlet and outlet Pond bottom should slope down to outlet 1.2 Pond cleaning Before PLs are released at 25-30 days, draining out pond water and drying pond bottom should occur from 7-10 days Plough pond bottom after removing mud toplayer If acidic bottom, repeating water flushing 2-3 times If it isn’t possible to dry the pond bottom due to natural conditions, wet cleaning method should be applied Using pump to drain pond bottom then using high pressure pump to remove mud top-layer If acidic bottom, repeating water flushing 2-3 times 1.3 Pond liming Use of CaO and CaCO3 in the ratio of 2:1 for disinfection and to increase bottom pH Pond bottom needs to be wet and pH checked before lime application in order to enhance lime effectiveness and right application amount Refer to below table as a reference pH bottom soil CaO/ha CaCO3/ha >6 1000 500 5-6 2000 1000 8.5): application of fine sugar 10-12 kg/ha, or drive water through bio-treatment system, or acid acetic produced by fermenting 10-15 kg rice bran in m3 pond water in days (extract supernatant only) 6) Oil film can be eliminated and skimmed using clean cloths or inner part of maize 7) Temperature stratification (mainly caused by heavy rain): draining out top layer water, operating mixing devices, and then Zeolite or Diatomite applied Research Institute for Aquaculture No & The University of West Australia 42 Environmental and Economic Evaluation of Shrimp Culture Practices in Vietnam IV HARVESTING AND MARKETING 4.1 Partial harvesting When an individual size of 25-30 g is reached If shrimp is not uniform in size use of grading device to catch targeted one 4.2 At once harvesting Drain out water for this method of harvesting Shrimp after smolting should not be harvested due to soft shell 4.3 Post-harvesting preservation As soon as harvesting, shrimp have to be washed and iced (ice/shrimp ratio is 1/1), transportation to processing unit directly 4.4 Critical role of community responsibility Community based-market can give an advantage in negotiation selling price and choosing right buyer, particularly when free disease shrimp produced Community plays an important role in the production chain, from production preparation to product marketing Research Institute for Aquaculture No & The University of West Australia 43 ... at the beginning of the cultivation period in all provinces, but fell to within the recommended range in Ha Tinh and Nghe An towards the end of the period, An increase in alkalinity in Ha Tinh... sources in TT-Hue, and for inlets and ponds in Ha Tinh and Nghe An (Figure 10) Sulphide levels were higher than recommended in the outlets in Nghe An, and in Ha Tinh at the beginning of the season Toxic... 7.94 8. 10 7.11 7.49 8. 36 8. 00 8. 18 8.50 8. 00 8. 19 8. 50 7.94 8. 15 8. 45 7.23 7 .83 8. 65 7.90 8. 23 8. 60 7.75 8. 37 8. 06 7.77 7.93 8. 43 7.99 8. 23 8. 45 7.39 7.79 5.61 5.16 5.41 5.21 4. 38 4.74 5.07 4.71