Impact of farm management on expression of early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) on penaeid shrimp farms in Thailand

Asian shrimp farming industry has experienced massive production losses due to a disease caused by toxins of Vibrio bacteria, known as early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) for the last 5 years. The disease can cause up to 100% cumulative pond mortality within a week. The objective of this study was to identify factors associated with AHPND occurrence on shrimp farms. A case–control study was carried out on shrimp farms in four provinces of Thailand. Factors related to farm characteristics, farm management, pond and water preparation, feed management, post‐larvae (PL) shrimp and stock management were evaluated. Multivariable logistic regression analysis identified factors affecting AHPND occurrence at the pond level. Chlorine treatment, reservoir availability, use of predator fish in the water preparation, culture of multiple shrimp species in one farm and increased PL stocking density contributed to an increased risk of AHPND infection, while delayed first day of feeding, polyculture and water ageing were likely to promote outbreak protection. Additionally, the source of PL was found to be associated with AHPND occurrence in shrimp ponds, which requires further study at the hatchery level. Identification of these factors will facilitate the development of effective control strategies for AHPND on shrimp farms.     

Assessment of household risk management strategies for coastal aquaculture: the case of clam farming in Thaibinh Province,Vietnam

Clam farmers have experienced different types of risks that have been further exacerbated by the rapid expansion of clam farming areas, increased growing densities, and increased market difficulties in recent years in the Thaibinh Province of Vietnam. Most farmers have been seriously affected by production risk, market risk, and financial risk, while a number of others have met with success in almost all of their clam-raising cycles. This study applied a differentiating comparative analysis method and multiple discriminant analysis method to discuss the differences in risk management strategies between and among clam farming households and the impacts of those differences on their success/failure rates. In general, the tactics are related to increase in farm size, the application of technical innovations, diversifying livelihood activities, and accessing secure financial sources all provided better conditions for clam growth, diminished losses, and led to speedier recovery from shocks. To support farmers in managing risks, several government interventions are needed: (1) better re-zoning of clam farming areas in parallel with an increase in the farm size of each household, (2) promoting sustainable linkages between the farmers and the formal financial market and output market, and (3) investing more funding into research and extension related to sustainable clam farming practices and to the improvement of farmers’ skills in cooperative works and management.     

COVID-19 impacts on the Bangladesh shrimp industry: A sequential survey-based case study from southwestern Bangladesh

Shrimp farming is fundamental to the national economy of Bangladesh, particularly through earning foreign currency. The nationwide lockdown and international cargo restriction jeopardized the sector and breaking its marketing chain. Assessing the degree of farming socio-economic peril from COVID-19 and suggesting early coping strategies and long-term mitigation measures are pressing to build resilience for this food production sector. To collect survey data, two key-informant face-to-face surveys with 51 shrimp farmers and 62 consumers in southwest Bangladesh were accomplished. As national lockdowns restricted access to export markets and movements within the country, farm incomes decreased against rising production costs. To compensate, farmers reduced their workforce (29.4%), but even with the sale of co-cultured finfish still suffered from large drops in revenue (42.8% average profit reduction). Furthermore, we present evidence that shrimp farmers should consider diversification of aquaculture product type as co-culture of additional shrimp species was a poor mitigation strategy against large market price fluctuations. Product price reductions were passed on to the consumer, who enjoyed falling product prices including more expensive shrimp products, but the markup for nearly all aquaculture products increased. The current jeopardy and consequences of shrimp farming future are discussed, including coping strategies to help policymakers in building resilience against future uncertainties.

     

Biosecure Shrimp Feeds and Feeding Practices: Guidelines for Future Development

For the purposes of this paper, biosecure shrimp feeds and on‐farm feeding strategies refer to the “feed, whether live, fresh, or formulated, and the management of the feed on the farm, should not be an entry point of potential pathogens to the shrimp and/or to the culture system.” The paper reviews the different feeds commonly used for the production of farmed shrimp and discusses their potential risks from a disease perspective, including the use of live hatchery and nursery feeds, the use of live and/or fresh food organisms for the production of broodstock, and the use of dry formulated shrimp feeds for shrimp growout operations. In addition, the paper discusses the critical role played by feed‐processing techniques for the pasteurization and destruction of pathogens within shrimp feeds and the need for nutritionists to formulate feeds for optimal nutrition and health, and not just for optimal growth. The importance of the development and implementation of good on‐farm feed management practices by farmers is discussed, including the prohibition of the top‐dressing of pelleted feeds on farm by farmers with unapproved feed additives such as antibiotics. Finally, the paper discusses the responsibilities of farmers, feed manufacturers, and traders regarding the development and use of recommended biosecure shrimp feeds and feeding practices.     

PERCEPTIONS OF RISK AND RISK MANAGEMENT IN VIETNAMESE CATFISH FARMING: AN EMPIRICAL STUDY

Although Vietnamese catfish farming has grown at a rapid rate in recent years, the industry has also faced many problems that affect its sustainability. This paper explores the perceptions of catfish farmers regarding risk and risk management strategies in their production activities. The relationships between farm and farmer socioeconomic characteristics and perceptions of risk and risk management are also examined. Data for the study were collected in 2008 from a sample of 261 catfish farmers in the Mekong Delta, Vietnam using a questionnaire survey. The results show that, in general, price and production risks were perceived as the most significant risks. Farm management and technical measures were perceived to be more effective than other kinds of risk management strategies in risk reduction. Although price risks were rated as important, price risk management strategies were not perceived as important measures for risk mitigation. The results of the study are discussed to identify the implications for various industry stakeholders, including policymakers, processors, advisors, and developers of new risk management strategies.     

EFFICIENCY ANALYSIS AND THE EFFECT OF POLLUTION ON SHRIMP FARMS IN THE MEKONG RIVER DELTA

This article investigates the efficiency of intensive, semi-intensive, and extensive shrimp farming practices as well as the difference between the upstream and downstream efficiency of shrimp farms in the Mekong River Delta (MRD), Vietnam. Our article is the first to compare the efficiency of the 3 shrimp practices and investigate the difference between the efficiency of downstream and upstream farms. The efficiency of shrimp farms is measured using group-frontier and meta-frontier analysis on a sample of 292 farms. The results show that, on average, shrimp farms are inefficient; extensive farms are more efficient than intensive and semi-intensive farms; and, controlling for key socio-economic factors, upstream farms are more efficient than downstream farms, suggesting that pollution from upstream farms may influence shrimp farm efficiency. The results give some direction for improvement and some evidence to shrimp farmers and policymakers in the MRD to take the pollution problem seriously and find solutions for more sustainable development.     

A DEMAND ANALYSIS FOR CRUSTACEANS AT THE U.S. RETAIL STORE LEVEL

This study used a LA/AIDS model to estimate demand system for crustacean species, shrimp, crab, crawfish and lobster at the U.S. retail store level. Shrimp demand is price elastic; crab, crawfish and lobster are price inelastic. Shrimp price significantly affects market shares of crustacean products. Shrimp has more substitutes than other crustaceans, and lobster has less substitutes than others. The demand for crab and lobster grow faster than the demand for shrimp and crawfish when expenditure increases. Promotion has positive effects on market shares and sales volume of own products and negative effects on cross-products. Shrimp price-reduction promotion strategies will be effective in term of raising shrimp sales value. Marketing programs that increase consumers’ marginal utility with an additional small increase in the selling price of crab, crawfish and lobster products will be feasible, and bring higher sale values.     

Economics of risk and uncertainty of alternative water exchange and aeration rates in semi‐intensive shrimp culture systems

Abstract

Reducing water exchange in shrimp aquaculture to minimize discharge of pollutants is a search for sustainability. In desert regions, like most of northwest Mexico, low water exchange must be complemented with artificial aeration to compensate for low levels of oxygen in warm and highly saline water. The economic yield of a low‐water‐exchange production system is compared against yield from a typical water‐exchange‐without‐aeration system for Penaeus vannamei culture. The difference between two systems is centered on pumping and aeration rates for a 100 ha semi‐intensive farm in northwest Mexico.

A bioeconomic model was built to compare the systems. Risk analysis is adopted to account for uncertainty of seed price, shrimp growth rate, survival rate, and shrimp prices.

The typical system was slightly more profitable than the low‐water‐exchange, aerated system. The latter used less electricity than the former in all of the three mortality‐rate scenarios. However, the difference in profitability is so small that for practical purposes both production systems provide similar economic yield. For a typical system, the probability of reaching a positive net present value (NPV) is high, therefore under the assumed risks, a 100 ha semi‐intensive shrimp farm in northwest Mexico is a good investment choice.     

Economics of Sustainable Intensification of Aquaculture: Evidence from Shrimp Farms in Vietnam and Thailand

There is growing interest in sustainable intensification of aquaculture production. Yet little economic analysis has been done on farm‐level effects of the economic sustainability of production intensification. Data from 83 shrimp farms (43 in Vietnam and 40 in Thailand) were used to identify (through principal component and cluster analyses) 13 clusters of management practices that reflected various scales of production intensity that ranged from 0–1999 kg/ha/crop to 10,000 kg/ha/crop and above, for both Penaeus monodon and Litopenaeus vannamei in Vietnam and Thailand. The clusters identified reflected sets of management practices that resulted in differing yields despite similarities in stocking densities among some clusters. The enterprise budget analysis developed showed that the more intensively managed clusters outperformed the less intensively managed clusters in economic terms. More intensively managed farm clusters had lower costs per metric ton of shrimp produced and were more profitable. The greater yields of shrimp produced per hectare of land and water resources in more intensively managed shrimp farms spread annual fixed costs across a greater volume of shrimp produced and reduced the cost per metric ton of shrimp. Costs per metric ton of shrimp produced decreased from the lowest to the highest intensity level (from US$10,245 at lowest intensity to US$3484 at highest for P. monodon and from US$24,301 to US$5387 for L. vannamei in Vietnam and from US$8184 at the lowest intensity level to US$3817 at the highest intensity level per metric ton for L. vannamei in Thailand). Costs of pond amendments used in shrimp production were particularly high in Vietnam and largely unwarranted, whereas fixed costs associated with the value of land, production facilities, equipment, and labor were sufficiently high in Thailand so that net returns were negative in the long run. Nevertheless, economic losses in Thailand were less at greater levels of intensification. The study demonstrated a clear value proposition for shrimp farmers to use natural resources (such as land) and other inputs in an efficient manner and supports findings from corresponding research on farm‐level natural resource use efficiency. Additional research that incorporates economic analysis into on‐farm studies of sustainable intensification of aquaculture is needed to provide ongoing guidance related to sustainable management practices for aquaculture.     

White spot syndrome virus epizootic in cultured Pacific white shrimp Litopenaeus vannamei (Boone) in Taiwan

White spot syndrome virus (WSSV) has caused significant losses in shrimp farms worldwide. Between 2004 and 2006, Pacific white shrimp Litopenaeus vannamei (Boone) were collected from 220 farms in Taiwan to determine the prevalence and impact of WSSV infection on the shrimp farm industry. Polymerase chain reaction (PCR) analysis detected WSSV in shrimp from 26% of farms. Juvenile shrimp farms had the highest infection levels (38%; 19/50 farms) and brooder shrimp farms had the lowest (5%; one of 20 farms). The average extent of infection at each farm was as follows for WSSV‐positive farms: post‐larvae farms, 71%; juvenile farms, 61%; subadult farms, 62%; adult farms, 49%; and brooder farms, 40%. Characteristic white spots, hypertrophied nuclei and basophilic viral inclusion bodies were found in the epithelia of gills and tail fans, appendages, cephalothorax and hepatopancreas, and virions of WSSV were observed. Of shrimp that had WSSV lesions, 100% had lesions on the cephalothorax, 96% in gills and tail fans, 91% on appendages and 17% in the hepatopancreas. WSSV was also detected in copepoda and crustaceans from the shrimp farms. Sequence comparison using the pms146 gene fragment of WSSV showed that isolates from the farms had 99.7–100% nucleotide sequence identity with four strains in the GenBank database – China ( AF332093 ), Taiwan ( AF440570 and U50923 ) and Thailand ( AF369029 ). This is the first broad study of WSSV infection in L. vannamei in Taiwan.     

Comparing Profits from Shrimp Aquaculture with and without Green-Water Technology in the Philippines

To reduce disease impact, Philippine farmers developed the green-water (GW) system, which has been spreading rapidly since 2008. In the most applied GW-system, the shrimp pond receives water from a reservoir stocked with tilapia. We collected financial data on GW and non-GW systems from farms having similar management and environmental context. All farms had more than one pond; the average pond area was < 1 ha, and total pond areas per farm ranged from 1.4 to 139 ha. The total variable and fixed costs per ha of shrimp pond were not different for GW and non-GW farms, but on GW farms the cost per kg of shrimp produced was lower. The latter was higher than the 2009 market price of 30 g shrimp for non-GW farms mainly. In GW farms the cost of seed was lower, and survival rates and individual shrimp weights at harvest were higher for an equally long culture period.     

Economic Evaluation of Different Stocking Densities for Various Sized in Texas

There has been a trend toward intensification of shrimp farming in the U.S. FiCteen simulated farms were used to evaluate economies of scale and to compare three Penaeus vannclmei commercial production strategies: semi-intensive, intensive, and very-intensive. Large economies of scale were associated with each production strategy. Over the range of farm sizes considered, investment cost per hectare decreased approximately 50% and production cost decreased approximately 25%. Farms' returns were measured with Internal Rate of Return (IRR). When investment was greater than $0.75 million, the intensive strategy provided slightly better returns to the investor than semi-intensive or very-intensive strategies. At investment levels less than $0.75 million, the semi-intensive strategy provided the highest IRR.     

Technical Efficiency of Shrimp Farming in Bangladesh: An Application of the Stochastic Production Frontier Approach

This study estimates the levels and determinants of farm‐level technical efficiency of shrimp farmers, using the stochastic production frontier function involving a model for technical inefficiency effects. A sample of 90 brackish water shrimp farms were surveyed in the region of Shyamnagar Upazila of the Satkhira District, Bangladesh, to study their economic efficiencies. Data were collected, using a questionnaire survey from September to October 2011. The mean technical efficiency level of the shrimp farmers was estimated at 82%, and thus, farmers operate 18% below the production frontier. The results suggest that the inefficiency effect is significant, and that education, age, non‐farm income and distance of the farm are significant determinants of technical inefficiency. By operating at full technical efficiency levels, shrimp production can increase from the current yield of 225.56 to 265.28 kg/ha. Besides improving technical efficiency, technological progress and extension services (such as dissemination of proper information of the technological practices and further adoption of technological practices) can also contribute to increased shrimp production levels. Finally, quality feed and fingerling at affordable prices need to be ensured to further promote shrimp production.     

舟山地区大棚凡纳滨对虾生长缓慢病因的调查分析

2013年以来,浙江省舟山地区大棚养殖的凡纳滨对虾(Penaeus vannamei)普遍出现生长缓慢、养殖成功率低的现象。为了查明该原因,本研究采用分子生物学和组织病理学等方法对引起对虾生长缓慢的病因开展了调查分析。结果显示,采集的270份病虾样本中,对虾肝肠胞虫(Enterocytozoon hepatopenaei,EHP)PCR阳性检出率高达85.19%,传染性皮下及造血器官坏死病毒(infectious hypodermal and hematopoietic necrosis virus,IHHNV)检出率为0;所有采集的病虾样本中也未分离到常见的致病菌;54份正常的对虾样本中EHP和IHHNV均未检出。将病虾PCR扩增产物进行序列测定和比对分析,结果获得的序列片段与Gen Bank中已有EHP相关序列相似性高达99.55%;病虾的肝胰腺组织病理切片观察显示,在虾肝胰腺组织中可观察到处于各个生长发育阶段的EHP。通过上述研究,初步认为EHP是引起舟山地区大棚养殖对虾生长缓慢的一个重要病原。     

Productivity assessment of an intensive whiteleg shrimp Penaeus vannamei farm based on Powersim-simulated growth rates

The main objective of intensive whiteleg shrimp Penaeus vannamei cultivation is to obtain high productivity to meet market needs. One of the efforts to boost production is to provide optimal feeding to increase the shrimp growth rate. This study analyzes the productivity of an intensive shrimp farm using Powersim simulations based on specific growth rates (SGR) and average daily growth (ADG) to determine the resulting production criteria. The cultivation lasted for 90 days by stocking 16 grow-out ponds with post-larvae (PL10) at a density of 80 PL per m². Shrimp samples were weighed every 10 days after day-30 of culture until harvest. The average productivity obtained from this study was 8.86 t/ha/crop. According to our criteria, this productivity level was low, presumably, due to the low growth rate that may have resulted from low-quality larvae, sublethal nitrite concentrations, low survival rate, and high feed conversion ratio. The SGR-based and ADG-based simulations using Powersim Studio 10 Express confirm the low production, which does not meet the criteria for intensive farming. However, ADG-based simulation shows that the prolonged culture to 126 days results in higher shrimp production and productivity that fall into the lower level of the intensive system. This study also proposes production criteria and productivity ranges for whiteleg shrimp farming.

     

EXTERNALITIES,INSTITUTIONS AND THE LOCATION CHOICES OF SHELLFISH PRODUCERS: THE CASE OF BLUE MUSSEL FARMING IN THE MONT-SAINT-MICHEL BAY (FRANCE)

ABSTRACT

Most marine aquaculture activities remain strongly dependent on coastal ecosystems. In the case of shellfish farming, this dependency is related mainly to water quality and to the various ecological interactions resulting from the dynamics of coastal food webs. Such ecological constraints have influenced the overall evolution of blue mussel farming in the Mont-Saint-Michel Bay, leading producers to negotiate collective arrangements regarding production capacity and techniques and to develop production strategies at the farm level. This article presents an analysis of the location choices of mussel farmers in the Mont-Saint-Michel Bay based on an empirical investigation conducted in 2002. A typology of farms with respect to their land structure is developed in which some farms choose to concentrate their activity in a single part of the bay while others distribute their activity more widely. Determinants of the location choices of each farm category, including distance to port, natural productivity differentials, and predation of mussel stocks, are analyzed. The role of the institutional arrangements allowing mussel farmers to develop these location strategies is also discussed.     

Nitrogen dynamics in the settlement ponds of a small-scale recirculating shrimp farm (<Emphasis Type="Italic">Penaeus monodon</Emphasis>) in rural Thailand

Rural shrimp farmers in Thailand are being encouraged to adopt practices that will reduce the quantity and improve the quality of their effluent. A simple and cheap option for small-scale shrimp farmers is to use settlement ponds to store and remediate discharge water before being re-used. We undertook a detailed study of the settlement ponds in a small-scale commercial black tiger shrimp farm typical of rural Thailand. We found that over a 9-week period, following the harvest of one of the two farm production ponds, total nitrogen (TN) concentrations in the water column were reduced by 30%, with the greatest removal (56%) occurring during the fifth week. There was a 10% increase in dissolved organic nitrogen (DON) concentrations during the trial. Sediments were a source of total ammonia nitrogen (TAN), and the re-mineralisation rate was the highest in the first two settlement ponds. Coconut fronds added to two of the four settlement ponds to increase the surface area available for microbial activity were found to provide a site for microbial re-mineralisation of TAN, the photosynthetic uptake of TAN and oxidised nitrogen (NO _x ) and nitrification. The water column was a net assimilator of TAN through autotrophic uptake. This study has shown that settlement ponds are capable of reducing water column N concentrations; however, sediment must be managed to reduce re-mineralisation during successive cropping cycles. In addition, coconut fronds were shown to improve N removal, although they should be periodically removed to maintain efficiency.     

Transport limitation of oxygen in shrimp culture ponds

A 120-acre shrimp farm located in southeast Texas has failed for three years to produce expected yields of shrimp despite intensive management. Data obtained from these ponds are combined with observations from other culture facilities to support the hypothesis that the degree of mixing of pond water is the primary limitation to oxygenation of the benthic biomass in a shrimp culture pond. The implication of this conclusion is that shrimp ponds are advection limited; therefore, rational design of such facilities will require detailed data concerning the impact of interactions of pond size, depth and geometry with wind speed, and aerator placement, upon pond mixing.     

The evolution of farm management,production efficiencies,and current challenges to catfish production in the United States

Abstract

The catfish industry is the most successful aquaculture business in the US. The development and growth of the catfish industry has resulted in complex fish farm businesses that require intensive management. Technological innovations have resulted in increased yields (land use efficiency). However, in more recent years, productivity gains have not kept pace with the rate of increase in input costs. Increasing intensification of catfish production over time has been accompanied by increased use of debt capital that results in higher levels of financial risk. While still a profitable activity, real profit margins have declined as financial risk has increased. New technologies will likely continue to increase productivity over time. Market‐oriented agribusiness approaches to catfish marketing are likely to become the norm. The challenge for the catfish industry is to coordinate adoption of new higher‐cost technologies with demand increasing market development to sustain farm price levels.     

Production risk,technical efficiency,and input use nexus: Lessons from Bangladesh aquaculture

The optimal use of resources in aquaculture is important, especially in developing countries, to obtain the highest possible outcome from the production process to support food security and poverty alleviation. Thus, within this study, the risk, efficiency, and input‐use variation in aquaculture farms in Bangladesh is investigated using a flexible stochastic frontier model with a risk and an inefficiency function. The results reveal that feed, labor, and capital have positive and significant impacts on production. In addition, an increased fingerling density and a larger farm increase the risk, whereas the use of feed and the capital invested have the opposite effect. Access to extension services has a positive effect and increases farm efficiency. An investigation of the farm size–productivity inverse relationship reveals that this phenomenon is not applicable to Bangladesh aquaculture. In general, efficient farmers are large‐scale farmers, who use a lower stocking density but a higher feeding intensity, resulting in a higher yield. On average, farmers use less labor and feed than what is optimal. To increase efficiency and reduce risk, it is recommended that more technical knowledge on optimal input use, extension service, and capital is made available to aquaculture farmers.