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.     

THE IMPACT OF PRICE AND YIELD RISK ON THE BIOECONOMICS OF RESERVOIR AQUACULTURE IN NORTHERN VIETNAM

A bioeconomic model of reservoir aquaculture in northern Vietnam is used to investigate the impacts of fish price and yield variability on the level and riskiness of expected net revenue. Net revenue is volatile compared with similar enterprises in other countries, mainly due to high yield variability. This reflects the nascent nature of the industry in Vietnam and the potential for efficiency and productivity improvements. Increasing production intensiveness, as well as reservoir size, was found to increase profits and decrease revenue risk. Among the management parameters studied, expected net revenue was found to be most sensitive to the length of the production cycle and to the harvest rate, while revenue risk was most sensitive to cycle length. Reservoir size was found to affect net revenue less than anticipated. Although common carp monoculture was found to maximize expected profit, the current species mix minimizes risk, thereby suggesting high risk aversion by northern Vietnam's poor farmers.     

军曹鱼近海浮绳式网箱养殖技术

一、概述 海南省内港浮排式网箱养鱼生产规模截至1999年底已迅速发展到31635口(规格为3m×3m×3m),总产量达3624t,由于在那有限的港湾内盲目、无序地增网设箱,浮排布局杂乱无章,以致生产失控,远远超过了内港水体的承受能力,导致养殖环境恶化加剧,各种病害蔓延日趋严重,使内港浮排式网箱养鱼生产难以为继。     

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.     

BIOECONOMICS OF CAPTURE-BASED AQUACULTURE OF COD (GADUS MORHUA)

This study formulates and parameterizes a bioeconomic model of capture-based aquaculture (CBA) of cod (Gadus morhua). The model is solved for the optimal harvest pattern and calculates economic profit and net present value for a model farm. The biological sub-model incorporates knowledge from interviews with existing farmers, research trials and existing cod aquaculture literature. Economic components are obtained from interviews and sales statistics from exporters. A farm of the modeled scale is likely to influence market prices, hence sales prices were estimated assuming a supply response based on the price elasticity. Taking into account the opportunity cost of selling the fish directly, NPV is found to be marginally positive. Sensitivity analysis revealed that profitability is sensitive to changes in several parameters. Hence, further research is valuable and care should be taken when considering investments in cod CBA.     

螯合剂EDTA的性质及其在水生生物培养与育苗中的作用

随着工农业生产的发展，水域污染日趋严重，给水产增养殖业中的关键环节——育苗，带来了困难，使水质成为当前水产养殖(aquaculture)业的重要问题。无机金属离子的污染是造成育苗成败的关键因素之一。1974年，Wood从对水生生物有害的观点出发，将环境污染元素划分为三类(表1)。     

BIOECONOMICS OF INVASIVE SPECIES IN AQUATIC ECOSYSTEMS

When a biological invader is identified in an aquatic ecosystem, rapid response is critical, particularly if the invasive organism has the ability to spread rapidly. The first response should be to attempt to contain the invasion while further information is gathered to evaluate whether eradication is feasible. The eradication versus containment decision is studied by developing and using a stochastic dynamic programming model based on a simple biological spread function. Information requirements to calibrate the decision model for a specific invader are discussed and numerical analysis is undertaken to illustrate how the model can be used when only rough estimates of benefits and costs are available.     

Pond Culture of Larval and Juvenile Cobia,Rachycentron canadum,in the Southeastern United States

Abstract

The potential of growing larval and juvenile cobia, Rach-ycentron canadum, in ponds was investigated. Larval cobia, obtained from tank spawning of wild-caught adults, were stocked 48-72-h post-hatch at a rate of 700,000/ha into three fertilized 0.25-ha ponds. At one week post-stocking (WPS), fish were observed consuming formulated feed. Growth was rapid, with specific growth rates (SGR) ranging from 12.5-19.2% body weight/day. At harvest (5 WPS) fish reared in two ponds weighed 7.9 and 9.3 g and total length (TL) was 118.9 and 129.3 mm, respectively (all fish reared in remaining pond died the night prior to harvest due to aerator failure). Feed conversion ratio (FCR) was 3.8 for both ponds and survival was 5.3 and 8.5%. Low survival rates were thought to be due primarily to cannibalism. Immediately after harvest, fish were restocked into two 0.25-ha ponds at a stocking rate of 14,400/ ha. Fish were fed formulated, pelleted feeds. Growth was rapid up to ～9 WPS, after which pond water temperatures declined. Ponds were harvested at 13 and 15 WPS, respectively. Final weight of fish was 309.9 and 362.5 g. Final TL was 343.1 and 355.7 mm. FCR was 3.8 and 4.5 and survival was 27.5 and 30.5%. Major losses of fish were associated with avian predators and possibly a toxic algal bloom. Results of trials indicate that cobia larvae and juveniles can be reared in pond-based culture systems, however additional research is needed to refine this approach.     

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.     

VALUE CHAIN OF SNAKEHEAD FISH IN THE LOWER MEKONG BASIN OF CAMBODIA AND VIETNAM

Snakehead fish are the most preferred fish species for food in Cambodia and Vietnam, and are consumed in both fresh and processed forms. The purpose of this paper is to describe the value chains of captured and cultured snakeheads in the Lower Mekong Basin (LMB). The important actors involved in the value chain of snakeheads in the LMB of Cambodia and Vietnam were fishers, fish farmers, wholesalers, retailers, and processors. The value chain of wild captured snakeheads in Cambodia was focused on 11 marketing channels, and for cultured snakeheads in Vietnam, 10 market channels. The distribution of benefits among the chain actors was unequal, with the highest proportion of profit going to wholesalers in Cambodia and collectors in Vietnam. In order to develop the value chain of snakehead for the long-term in the LMB, appropriate plans must be prepared for each country in association with better management and protection of natural aquatic resources.     

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.     

Impacts of climate change on snakehead fish value chains in the Lower Mekong Basin of Cambodia and Vietnam

ABSTRACT

The productive fisheries of the Lower Mekong Basin of Cambodia and Vietnam are essential to the food security and nutrition of 60 million people. Yet these fisheries, both culture and capture, are susceptible to the impacts of climate change. This article reports on a study undertaken to examine the vulnerability, as perceived by snakehead (Channa striata) fish farmers in Vietnam and fishers in Cambodia, to the impacts from climate change. Perceived impacts on various actors in the value chain are identified, as well as adaptation strategies currently being utilized and planned for the future. Recommendations are suggested to contribute to assisting snakehead farmers and fishers in adapting and preparing for the impacts of climate change.     

浆叶式增氧机在养鳟中的应用计算

本文论述了浆叶式增氧机在虹鳟鱼高产养殖中的应用计算方法。此法可算出增氧机使用条件下的动力和鱼污所用增氧机的数量。     

COMPARISON OF AQUACULTURE EXTENSION IMPACTS IN BANGLADESH

ABSTRACT

Production from small scale pond aquaculture in Bangladesh trebled in the decade to 1999 under the influence of extension projects of the Department of Fisheries. The impacts of completed aquaculture extension projects and practices of former participants have rarely been investigated so this was done for four past projects. The different extension approaches were: extension with credit and intensive or little supervision; demonstrations; group extension and informal extension by fry traders; and adaptive research-development. Generally extension recipients and non-participants had similar sized landholdings, but demonstration farmers had larger farms and ponds. Extension recipients mainly received information from project-related sources and rated its utility highly. Neighbours and control farmers mainly obtained information from mass media and other farmers, over 90% of these households also cultivated fish. Extension recipients generally followed better practices: for example stocking fewer fingerlings and achieving higher production than non-participants, but with wide variations. Training of fry traders appeared to reduce overstocking in general probably due to the advice of fry traders. Overall, 2–6 years after extension the recipients have continued to farm fish, have a fair understanding of good practice and achieve reasonable yields. Limited demonstration effects occurred. Extension through group approaches and informal agents seem to be cost effective for the many pond owners in Bangladesh.     

SOCIOECONOMIC INTERACTIONS OF FISHERIES AND AQUACULTURE IN GREECE: A CASE STUDY OF SOUTH EVOIKOS GULF

The present study investigates the socioeconomic sustainability of fisheries and aquaculture in the South Evoikos Gulf. The results show poor labour mobility between fisheries and aquaculture. Internal geographical mobility, relatively high salaries and the relatively high educational level of the aquaculture workers contribute to the sustainability for the aquaculture sector. There is a high probability of young, low-educated individuals entering the fishing industry. Furthermore, earnings and professional training prevent people from exiting the fisheries sector, and this may act as a means towards fisheries' sustainability. Grants and subsidies do not seem to influence fishermen's decision to remain or exit the sector. On average more fishermen than aquaculture workers perceive that their profession is supported by the local community and tourist industry.     

厦门港尖额真猛水蚤室内培养的研究

由厦门港潮间带筛选的小型桡足类——尖额真猛水蚤(Euterpe acutifrons),在鱼、虾育苗中具有明显的应用价值。进行周年室内培养试验,单一雌体生命周期67天,培养两个半月后,个体数达15万个,平均培养密度3689个/升,日增殖率0.149。夏季怀卵10次,间隔3—9天,总怀卵量174个;冬季怀卵3次,间隔12—16天,总怀卵量86个。使用单种饵料——微型黄藻的异胶藻(Heterogroea sp)周年培养该种桡足类是可行的。饵料浓度以100×10~4个/毫升较适,当350×10~4个/毫升时繁殖尚顺利,但在850—1680×10~4个/毫升以上,生长繁殖受抑制,浓度太高甚至死亡。     

开放性海域网箱养殖黑鲪技术

北方地区的海水网箱养鱼自20世纪90年代有了长足的发展,但由于受水温制约,海水网箱养鱼品种仅有鲈鱼、鯛、河豚、美国红鱼、牙鲆、六线鱼等,比较单一。而开放性海域网箱养鱼,受风浪、养鱼品种等制约,进展尤其缓慢。大连碧龙海珍品有限公司1999年选用单体柔性网箱、单体浮式网箱、单体沉性网箱、单体沉浮式网箱,及鲈鱼、真鯛、河     

PERI-URBAN OYSTER FARMING IN THE UPPER GULF OF THAILAND

Oyster farming is an important source of income in many coastal communities throughout Asia. Little is known, however, about the productivity of the farming systems used and the challenges faced by growers. This paper presents the results of a study undertaken in the small peri-urban coastal community of Ang Sila on Thailand's eastern seaboard. The community is located in one of Thailand's most important oyster production areas, and is dominated by small farms that use simple semi-traditional culture techniques. Farm attributes together with the personal characteristics and opinions of farmers were obtained from a survey of 30 oyster farm owners. A typical farm of 100,000 strings was found to produce a net profit of approximately 90,000 baht ($2250 USD). A high level of female participation in farm ownership was also identified that benefits women with relatively low levels of education and limited economic opportunities. Peri-urban coastal areas in Thailand cannot currently produce export quality shellfish owing to water quality concerns. Improved growing water management techniques and the introduction of seafood safety protocols could, however, improve the quality of oysters sold to domestic consumers and provide a basis for developing export opportunities in the future.     

对虾养殖池沉积环境中TOC_TP_TN和pH垂直分布

１９９５年冬季,测定了青岛地区四个池龄１０年以上的对虾养殖池不同层次沉积物中有机碳（ＴＯＣ）、总氮（ＴＮ）、总磷（ＴＰ）和ｐＨ并研究了其垂直分布。结果表明,沉积物中的ＴＯＣ和ＴＮ污染较底层严重,泥质虾池表层污染较泥沙质更严重。沉积物中ＴＰ为输出过程而导致缺乏,ＴＰ的受扰动层与ＴＯＣ和ＴＮ的污染层基本一致。沉积物的ｐＨ无规律性变化。     

Water and nutrient budgets of ponds in integrated agriculture–aquaculture systems in the Mekong Delta, Vietnam

A participatory on-farm study analysed water and nutrient budgets of six low and four high water-exchange ponds of integrated agriculture–aquaculture (IAA) farms in the Mekong delta. Water, nitrogen (N), organic carbon (OC) and phosphorus (P) flows through the ponds were monitored, and data on fish production and nutrient accumulation in sediments were collected during a fish culture cycle. Results showed that, on average, only 5–6% of total N, OC or P inputs introduced into ponds were recovered in the harvested fish. About 29% N, 81% OC and 51% P accumulated in the sediments. The remaining fractions were lost through pond water discharges into adjacent canals. Fish yields and nutrient accumulation rates in the sediments increased with increasing food inputs applied to the pond at the cost of increased nutrient discharges. High water-exchange ponds received two to three times more on-farm nutrients (N, OC and P) while requiring nine times more water and discharging 10–14 times more nutrients than the low water-exchange ponds. Water and nutrient flows between the pond and the other IAA-farm components need to be considered when optimizing productivity and profitability from IAA systems.