BIOECONOMICS OF RESERVOIR AQUACULTURE IN VIETNAM

Reservoir aquaculture has developed in an ad hoc manner in Vietnam to date. A bioeconomic model of reservoir aquaculture in northern Vietnam is presented in this paper to highlight issues of developmental importance of reservoir aquaculture in Vietnam. The biological model is based on a conventional von Bertalanffy growth function and the economic model is a net revenue function. The greatest source of costs for the operation are restocking costs (75%) and contract labor costs (18 percent). Benchmark net revenue is approximately 8.7 million VND (approximately US$539). The stocking density, length of time between stocking and harvest and harvesting efficiency have the largest impact on net revenue. The inclusion of aquaculture into government fisheries development plans with research focused on development of fingerling production, preparation of flooded land for aquaculture production and strengthening institutional arrangements for reservoir leasing and credit arrangements, is likely to lead to increased capitalization and investment, and therefore greater revenues for local fishing populations.     

MODELING THE IMPACT OF GOVERNMENT REGULATIONS ON THE PERFORMANCE OF RESERVOIR AQUACULTURE IN VIETNAM 1

This study was motivated by the need to estimate the quantitative impacts of current regulatory constraints on the economic performance of reservoir aquaculture in Vietnam. Using survey data and a specially adapted bioeconomic model, we show that performance of reservoir aquaculture varies widely. The three performance criteria were fish yields, net production revenue and income generated for the local population. Results suggest that current policies regarding extension effort on fingerling survival rates and on feeding strategies, as well as regulations involving taxation of cooperatives and authorities collecting leasing fees, do constrain the economic potential of reservoir aquaculture. The forgone production revenues limit the potential for aquaculture to alleviate local poverty. This study is a first step in identifying those government regulations that have a critical role in the development of reservoir aquaculture in Vietnam.     

闽台近海渔业管理目标的研究

本文应用Ｓｃｈａｅｆｅｒ和Ｆｏｘ两种剩余产量模式,及其由此衍生的两种生物经济模式,分别估算了闽台近海最大持续产量,最适捕捞力量和最大经济产量,最适经济捕捞 力量,最佳经济效益等指标,建立了闽台渔烽管理模式,比较了以最大渔获量和以最佳经济效益为目标的各项经济指标,讨论了并确定了近期以最大持续产量为目标的渔业管理方案。     

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.     

A COMPARISON OF THE ECONOMIC PERFORMANCE OF OFFSHORE AND INSHORE AQUACULTURE PRODUCTION SYSTEMS IN KOREA

The economic performance of the current inshore rock bream aquaculture industry conducted in Yeosu, Korea was compared with a pilot commercial scale offshore aquaculture farm in Jeju, Korea. Data was collected from 12 inshore farms and two production cycles of the offshore farm for use in Monte Carlo simulations run over a ten year time horizon. Net present value was compared for the inshore farms and two survival rate scenarios for the offshore farm. The offshore farm is expected to have a higher survival rate if it can withstand tsunamis and avoid pollution, disease and red tide impacts that are prevalent inshore. When the offshore farm was modeled with its observed higher survival rate, its average net present value ($1,016,483) significantly outperformed the inshore farms average net present value ($182,153). In the second scenario, the offshore farm survival rate was lowered based on performance data from the inshore farms. Not surprisingly, given the higher investment costs, the offshore farm performed poorly in terms of average net present value ($-137,142) compared to the inshore farms when it no longer had the advantage of high survival rates.     

放养在胜利水库中的匙吻鲟的生长

在黑龙江省青冈县胜利水库放牧式养殖了匙吻鲟（Polyodon spathula）,同时调查了水库的水质及浮游动物的种类组成和生物量,并随机设置挂网,不定期调查捕获匙吻鲟的生长状况。结果发现：该水库水质符合渔业水质标准（GB11607—89）,浮游生物的生物量较高。放养的匙吻鲟生长良好,当年可超过越冬规格;日平均增重3．31％,体长增长1．17％,结果表明：匙吻鲟适于在北方湖泊、水库等具备越冬条件的水体进行放牧式养殖。     

Relationship between body length, processed-meat length and seasonal change in net processed-meat yield of Japanese mantis shrimp Oratosquilla oratoria in Tokyo Bay

ABSTRACT:   There is concern regarding a possible decrease in the minimum exploitable size of the mantis shrimp Oratosquilla oratoria in Tokyo Bay, coincident with a decline in stock size. To assess this problem, the condition factor, the relationship between body length and processed-meat length, and the estimated body length for each market size category were investigated and compared monthly. The condition factor was lowest in spring and peaked in winter. The difference between body length and meat length was higher in summer and winter than in spring and autumn, suggesting that a high condition factor does not result in an increased net yield of processed meat. The annual mean minimum exploitable size in the present low-stock-size condition did not differ from the minimum exploitable size measured during a high-stock-size period (11-cm body length). However, the minimum exploitable size changed seasonally, which coincided with seasonal change in the net processed-meat yield. Exploitation during the season when net meat yield is high would result in increase of the large-sized meat products of high price.     

Tropical spiny lobster (Panulirus ornatus) farming in Vietnam – bioeconomics and perceived constraints to development

This paper presents bioeconomic data on lobster farming in Vietnam, and perceived constraints to the development of the industry. The farms were found to be profitable, with an average benefit cost ratio of 1.44 and an average net revenue of 262 million VND year^?1 (or just under US$15 000 year^?1). Investment in the enterprise is high compared with other enterprises in the region. However, disease has the potential to devastate lobster crops and there is little information available to lobster farmers about disease prevention and management. Hence, the lobster enterprise is a high‐risk high‐return industry. The predominant perceived constraints to the development of lobster operations include water quality and temperature issues, insufficient access to credit, good‐quality affordable feed and accurate information about technology improvements in lobster farming. It seems that improving the livelihood of lobster farmers in Vietnam is dependent on reducing their dependence on wild stocks for seed and feed, improving access to credit and improving technical and market information flows. Such improvements are likely to lead to higher profitability, given high export demand and hence sustained high prices for their lobster product.     

雪野水库网箱养鳜鱼试验

１９９７年７￣１０月在莱芜市雪野水库设置２７只网箱,进行鳜鱼养殖试验。总产鱼１２９５９．３ｋｇ,平均尾重１．２ｋｇ,商品率８６．５％,平均单产１９．２ｋｇ／ｍ＾２,最高单产２３ｋｇ／ｍ＾２,投入产出比为１：２．５７。试验认为,饵料鱼规格应控制在鳜鱼体长的４０％￣５５％,在网箱中设置隐蔽物,采用饱食投喂法,可以提高成活率,降低饵料系数。     

Growth and survival model of Pacific bluefin tuna (Thunnus orientalis) for capture‐based aquaculture in Mexico

Capture‐based aquaculture (CBA) is a strategy to capture wild aquatic organisms for rearing. The most iconic species produced under this scheme are bluefin tunas. In Mexico, CBA of this species is developed with Pacific bluefin tunas (PBFT). The parametrization of a biological production function able to describe biomass dynamics during the production cycle is one of the strategies that can help optimize production. The objective of this study was to explain biomass dynamics in capture‐based Pacific Bluefin tuna aquaculture in Mexican waters through parameterization of a growth and survival model. This study also assessed the impact of uncertain intrinsic CBA variables (i.e. seed weight, number of stocked individuals and sea surface temperature [SST] variability). The model was parameterized with production records of 47 net pens in two production sites (an offshore and an inshore facility) during three cycles. The results suggested that production performance was related to SST given that this factor affected survival, mainly during the first ≈40 days after stocking. The risk analysis showed that stocking during the second half of the fishing season from June to August increased the likelihood of matching or exceeding the Key Performance Indicator (KPI) defined regarding biomass increase per pen.     

不同规格和投苗密度对仿刺参池塘网箱保苗效果的影响

仿刺参室外池塘网箱保苗是近年来兴起的一种半生态式的保苗方式。于2014年7—11月在仿刺参室外池塘网箱保苗期间,通过现场试验比较研究了不同投苗规格[大规格(0.093±0.004)g/头,小规格(0.024±0.001)g/头]和密度(低密度125g/m3、中密度250g/m3、高密度375g/m3)两因素对仿刺参苗生长、成活率和产量的影响。结果表明,对于同一规格的仿刺参苗,低密度组体质量与特定生长率高于中、高密度组;相同密度条件下,大规格苗种成活率显著高于小规格(P0.05),小规格低密度组仿刺参苗的成活率显著高于高密度组(P0.05),大规格低密度组仿刺参苗的成活率显著高于中、高密度组(P0.05)。不同密度组收获仿刺参苗的总产量无显著差异(P0.05),但低密度组收获仿刺参苗的净产量高于中、高密度组。通过两因素方差分析可知,规格的主效应及二者的交互作用对仿刺参苗成活率有显著的影响(P0.05),密度的主效应对仿刺参苗成活率有极显著的影响(P0.001);两因素的主效应及其交互作用对仿刺参苗总产量均无显著的影响(P0.05)。规格主效应及二者的交互作用对仿刺参苗净产量的影响不显著(P0.05),密度主效应对仿刺参苗净产量有显著的影响(P0.05)。因此,仿刺参室外网箱保苗过程中投放大规格、低密度苗种能够保证较高的成活率和净产量,而且可以节省苗种资源和饵料投喂量,降低单位面积生产成本和管理成本,提高产出投入比和经济效益。     

Economic Effects of Intensification of Baitfish Production

This study analyzed the economic effects of intensifying baitfish production. An economic engineering approach was utilized to develop enterprise budgets for baiffish production that were used to conduct an economic analysis. All indicators utilized, including net returns, internal rate of return, and payback period, indicated dramatic improvement in the economics of baitfish production with yield increases. There were strong economic incentives to increase yield, and minnow production at industry average yield was only marginally profitable under certain scenarios and unprofitable under others. Yields of 600 kg/ha would generate adequate revenue to compete with other aquaculture alternatives in terms of net returns as well as generate M internal rate of return that would outperform current long-term interest rates.     

Bioeconomic analysis of intensive production of the blue shrimp Litopenaeus stylirostris (Stimpson)

A bioeconomic approach was used to evaluate random variation of growth and mortality parameters and feed conversion ratio (FCR) for intensive production of the blue shrimp Litopenaeus stylirostris (Stimpson). Severe mortality problems caused by high impact diseases were not considered in this analysis. For a 50‐ha farm, the maximum values of the internal rate of return (IRR=44%) and net revenue above operation costs (NR=US$1 211 000) were obtained for a stocking density of 67 postlarvae (PL) m^?2 during winter–spring (cycle 1) and 65 PL m^?2 during summer–autumn (cycle 2). Regardless of the density used for cycle 1, stocking at 50 and 65 PL m^–2 for cycle 2 sufficed to obtain, respectively, IRRs greater than the minimum attractive IRRs of 15% and 30%. A frequency distribution of IRR, projected for densities of 67 and 65 PL m^?2, showed high confidence in obtaining IRR values above 15% and 30% (i.e. confidence >99% and 92% respectively). The frequency distribution of NR showed that the farm could operate without economic losses. Stocking a minimum of 53% of the capacity of the farm would guarantee positive NR. Sensitivity analysis indicated that the IRR and NR were mainly influenced by mortality rate, selling price, density, final weight and FCR.     

架子网选型试验网模水槽试验报告

近几年，水产科技工作者相继研制出多种结构形式的架子网，试图解决架子网大量损伤幼鱼问题，最典型的有开口式、腹洞式、八片式三种，这些网在增产和释放幼鱼方面各具特色。为了选出一种最佳网型，我们于１９９１至１９９２年进行了架子网选型试验。选型以传统架子网为参照，三种典型为参选图，分别进行实网生产对比试验和网模水槽试验，优选出最佳网型。本文着重介绍网模水槽试验方法、内容及结果。     

Vulnerability of aquaculture‐related livelihoods to changing climate at the global scale

There is now a strong consensus that during the 20th century, and especially during recent decades, the earth has experienced a significant warming trend with projections suggesting additional further warming during the 21st century. Associated with this warming trend are changes in climate that are expected to show substantial spatial variability across the earth's surface. Globally, fish production has continued to increase during recent years at a rate exceeding that of human population growth. However, the contribution from capture fisheries has remained largely static since the late 1980s with the increase in production being accounted for by dramatic growth in the aquaculture sector. In this study, the distribution of vulnerability of aquaculture‐related livelihoods to climate change was assessed at the global scale based on the concept of vulnerability as a function of sensitivity to climate change, exposure to climate change and adaptive capacity. Use was made of national‐level statistics along with gridded climate and population data. Climate change scenarios were supplied using the MAGICC/SCENGEN climate modelling tools. Analysis was conducted for aquaculture in freshwater, brackish and marine environments with outputs represented as a series of raster images. A number of Asian countries (Vietnam, Bangladesh, Laos and China) were indicated as most vulnerable to impacts on freshwater production. Vietnam, Thailand, Egypt and Ecuador stood out in terms of brackish water production. Norway and Chile were considered most vulnerable to impacts on marine production while a number of Asian countries (China, Vietnam and the Philippines) also ranked highly.     

Cage culture of sutchi catfish, Pangasius sutchi (Fowler 1937): effects of stocking density on growth, survival, yield and farm profitability

The sutchi catfish, Pangasius sutchi (Fowler 1937) was grown at 10 stocking densities in cages suspended in a river‐fed channel during the summer of 2000. Catfish fingerlings (mean length 9.1–9.7 cm and mean weight 5.9–6.7 g) were stocked at densities of 60, 70, 80, 90, 100, 110, 120, 130, 140 and 150 fish m^?3. After 150 days, growth and yield parameters were studied and a simple economic analysis was carried out to calculate profitability. The mean gross yield ranged from 15.6±0.27 to 34.5±0.44 kg m^?3 and the net yield ranged from 15.2±0.22 to 33.5±0.36 kg m^?3 and showed significant variations (P<0.05). The mean weights of fish at harvest were inversely related to stocking density. Both gross and net yields were significantly different and were directly influenced by stocking density but the specific growth rate, survival rate and feed conversion rate were unaffected. Higher stocking density resulted in higher yield per unit of production cost and lower cost per unit of yield. The net revenue increased positively with increasing stocking density. A density of 150 fish m^?3 produced the best production and farm economics among the densities tested in this experiment.     

Effect of understocking density of channel catfish fingerlings in intensively aerated multiple‐batch production

Multiple‐batch production is the most widely practiced method of raising channel catfish. Producers are increasingly adopting intensified production practices in multiple‐batch systems by increasing stocking density and aeration rates as a means to improve cost efficiencies. Proven stocking recommendations are required for the efficient implementation of recent developments in multiple‐batch production. Twelve 0.4‐ha ponds were understocked with 17,484, 20,612, and 26,124 fingerlings/ha (mean weight = 40 g/fish) over equal weights of carryover fish (0.46 kg/fish @ 4,589 kg/ha). Fish were fed once daily to apparent satiation with a 28% protein floating feed and aerated with a single 7.4‐kW electric paddlewheel aerator. Density‐dependent significant differences were absent for gross, net, daily net yields, marketable yields (≥0.54 kg), growth (g/day), and survival. Sub‐marketable yield (<0.54 kg) and feeding rate increased significantly with increased understocking density. Economic analysis revealed increased breakeven prices and diminished net returns with increased stocking density when sub‐marketable fish were not considered as revenue. These differences in production costs and profits among the three treatments became minimal when sub‐marketable fish were included as revenue. All three density treatments attained positive annual net cash flows. This study validates channel catfish understocking densities of 17,000–26,000 fish/ha to improve cost efficiency in intensively aerated, multiple‐batch production systems.     

高产成鱼池蓝绿色裸甲藻水华的研究

由蓝绿色裸甲藻(Gymnodinium,sp．)形成的蓝绿色水华是无锡渔区高产鱼池典型水质之一。本文对该藻的形态特征、生态、池塘培育和控制以及对鱼类的影响进行了研究。蓝绿裸甲藻水华具喜温、喜光、喜有机氮肥,喜红褐色水色(生物因子),且对外界环境的变化十分敏感等生态特点。蓝绿裸甲藻水华池的理化条件较差,特别是藻体繁殖过度,极易恶化水质,造成鱼类泛池。采用增施有机氮肥、合理使用增氧机、加水等综合措施可促进和控制该藻的繁殖。经鱼类消化道镜检表明,蓝绿裸甲藻能被鲢、鳙鱼及鲤、鲫、罗非鱼鱼种大量摄食,并被鱼类消化。对无锡河埒渔业一队成鱼池三年统计,蓝绿裸甲藻水华池的鲢鳙鱼净产量比无水华池高33．4～37．5％。     

Production Characteristics and Economic Performance for Four Channel Catfish,Ictalurus punctatus,Pond Stocking Density-Cropping System Combinations

Fingerling channel catfish, "Ictalurus punctatus," were stocked into sixteen, 0.4-ha ponds at 11,120 fish/ha or 19.770 fish/ha. Half the ponds at either density were managed as single-batch cropping systems and half as multiple-batch cropping systems. Each of the four combinations in the 2 X 2 factorial design was replicated in four ponds over a 3-year study period. Ponds were not drained until the study was terminated. Average net fish production (totaled over 3 years) was 23,717 kg/ha for the single-batch, high-density treatment; 19,501 kg/ha for the multiple-batch, high-density treatment; 17,396 kg/ha for the single-batch, low density treatment; and 16,857 kg/ha for the multiple-batch, low- density treatment. Both stocking density and cropping system significatly (P < 0.05) influenced net production. Average size of fish at harvest was significantly (P < 0.05) lower at the high stocking density and in the single-batch cropping system. Feed conversion was better (P < 0.05) at the low stocking density and in the single-batch cropping systems. Poorer feed conversion in multiple-batch systems is believed due to harvest-to-harvest carryover of large fish, which convert feed to flesh less efficiently than small fish. Observed mortality and total fish loss (observed mortality plus fish unaccounted for upon termination of the study) were not affected (P > 0.05) by cropping system but were significantly (P < 0.05) higher in ponds stocked at the high density. Production data were used to assess discounted net revenues from a synthetic 131-ha farm based upon a price of $1.54/kg either for all fish harvested or for fish harvested that were ≥0.35kg. When based on all fish harvested, discounted net revenue was highest for the single-batch, high-density treatment, but the low average size of fish harvested from ponds in that treatment (0.49 kg/fish) would not be acceptable across the industry. The multiple-batch, low-density treatment had the second highest discounted net revenue based upon all fish harvested and the highest revenue when only fish ≥ 0.34 kg were valued. Of the treatments analyzed, this was judged the economic choice for the channel catfish industry.