Physico‐chemical characteristics of the improved extensive shrimp farming system in the Mekong Delta of Vietnam

Consecutive failure of the improved extensive shrimp farming system has deterred the economy of some coastal areas in Vietnam. To investigate pond physico‐chemical characteristics, a monitoring scheme was performed in the Cai Nuoc district of Southern Vietnam. Results show that the system was not optimal for shrimps. While ponds were not contaminated by organic loadings or major nutrients (N, P) and salinity and pH were most optimal for shrimp, more than 37% of dissolved oxygen (DO) measurements were lower than recommended. In the early morning hours, DO measurements were even much lower (0.84–2.20 mg L^?1). Sulphate (SO₄^2?) concentrations were most within the acceptable range. Total suspended solids (TSS) were above the acceptable limit (<50 mg L^?1). Iron, alkalinity and hydrogen sulphide were also higher than recommended. Pond sediment was anaerobic (redox potential ?422 to ?105 mV) and contained high amounts of organic matter (9.84–21.96%). Lethal DO levels, high TSS and anoxic sediment are the drawbacks in this system. Suggested measures to improve pond conditions are (1) allowing sedimentation before filling culture ponds, (2) covering dikes, (3) including no‐culture breaks between shrimp crops, (4) drying pond bottom, (5) removing sediment and (6) controlling pond's vegetation.     

A closer look into shrimp yields and mangrove coverage ratio in integrated mangrove-shrimp farming systems in Ca Mau,Vietnam

Shrimp aquaculture is the biggest source of export income in Vietnam. However, the development of the shrimp poses a serious threat to coastal mangroves by converting coastal mangroves into shrimp farms. Much effort has been made to replant mangroves and reduce the impacts of shrimp farming on the environment, and maintaining mangrove coverage at 30–50% of total farm area has provided the highest benefits in the integrated mangrove shrimp model. In this study, we re-examine the benefits of forest cover on the survival and yield of tiger shrimp (Penaeus monodon) in the integrated mangrove shrimp farming systems in Ca Mau province, Vietnam. The study found positive linear correlations of log transformed survival and yield of tiger shrimp with forest cover of the forms: Ln (survival)?=????1.39?+?0.038?×?forest coverage (r²?=?0.22; p value?=?0.0007); Ln (yield)?=?3.55?+?0.026?×?forest coverage (r²?=?0.16; p value?=?0.004). The households with high forest cover (i.e.,?>?45%) also had 1.07?±?0.29 and 1.39?±?0.36 (CI 95%, p value?=?0.000) kg ha^?1 higher yield per night harvest than those with medium and low forest cover, respectively. As a result, households with high forest cover have higher benefits than those with lower forest cover. Our findings together with previous published studies lead to the recommendation that farmers maintain mangroves in farming systems for better economic and environmental benefits.

     

Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan

Fisheries Science - Crustacean aquaculture is a multibillion-dollar industry worldwide that continues to show significant growth. Shrimp farming has been intensified for decades, and...     

The determinants of detecting veterinary drug residues: Evidence from shrimp farmers in southern Viet Nam

While export-oriented shrimp farming has become an important source of income for many small-scale farmers in developing countries, the rate at which products are rejected at the ports of developed countries has remained high mainly due to the overuse of antibiotics. To reveal what determines the overuse of antibiotics, we interviewed 201 shrimp farmers in Viet Nam in 2015 and collected shrimp samples from each household’s pond for the screening of residual drugs. These tests revealed that residual drugs exceeding acceptable limits by Japanese standards were found in the samples of 40 farmers. We conducted cross-sectional Logit and Tobit regressions to examine whether results of the residue tests are significantly associated with farmers’ characteristics and management practices. This study finds that: (1) receiving BMP training has a significant and positive effect on reducing residual drugs; (2) if farmers know multiple extension officers, these relationships have significant and positive effects on reducing residual drugs; and (3) farmers with experience of shrimp disease outbreaks reduce use of antibiotics. Overall, this study contributes to revealing the determinants of detecting veterinary drug residues in shrimp farming in multiple (social, economic and psychological) dimensions.     

Correction to: Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan

Fisheries Science - The article "Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan", written by Junpei Shinji,...     

Current status of farming practices of striped catfish, Pangasianodon hypophthalmus in the Mekong Delta, Vietnam

Aquaculture of catfish, Pangasianodon hypophthalmus (Sauvage), locally known as “ca tra”, and commonly referred to as striped catfish, river catfish and sutchi catfish, in Vietnam, having recorded a production of 683,000 tonnes in 2007, valued at about 645 million US$ is one of the largest single species based farming system, restricted to a small geographical area, in the world. The product is almost totally exported to over 100 countries as frozen fillets, as an acceptable alternative to white fish. Catfish is farmed mostly in earthen ponds, up to 4 m deep, in nine provinces in the Mekong Delta in South Vietnam. The results of the grow-out system of catfish farming in the Mekong Delta from a survey of 89 farms are presented. The farm size ranged from 0.2 to 30 ha with a mean of 4.09 ha. The frequency distribution of the yield in tonne/ha/crop and tonne/ML/crop corresponded to a normal distribution curve, where 75% of the farms yielded 300 tonnes/ha/crop or more. It was found that the yield per crop was significantly correlated (p < 0.05) to stocking density, pond depth and volume but not to pond surface area. Yields per crop was significantly different (p < 0.05) between upper and lower provinces of the Mekong Delta and water source (river versus channels), amongst others. It was evident that diseases and/or symptoms were observed to occur mostly in accordance with the onset of rains. In this paper the history of the catfish farming in the Mekong Delta is briefly traced, and current harvesting and marketing procedures as well as pertinent social elements of the farming community are dealt with.     

Aerator energy use in shrimp farming and means for improvement

Estimates of aeration energy use in shrimp farming varied from 11.4 to 41.6 GJ/t shrimp (average = 19.8 GJ/t). Several opportunities for reducing energy use in aeration are available. Many farms adopt an excessive yield to installed aeration capacity ratio. Moreover, the proportion of installed aerator capacity in use and duration of aerator operation per day are often more than necessary during the initial two‐thirds of grow‐out, because adjustment is not made for the quantity of shrimp biomass. Farm‐made, long‐arm aerators used in Asia have several features leading to energy inefficiency and could be replaced by more efficient factory‐made, long‐arm aerators. Asian aquaculture aerator manufacturers should redesign aerators to include design features shown in research to improve efficiency. Dissolved oxygen concentration monitoring essential for verification of aeration performance is seldom performed by shrimp farmers. With good aeration technique, energy use for aeration should not exceed 10–15 GJ/t shrimp.     

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.     

全价配合饲料在虾蟹健康养殖中的作用与技术

随着虾蟹养殖业的迅猛发展,做好虾蟹健康养殖工作,减少各种病害侵扰,提高养成率,保持效益稳定增长,已经刻不容缓地提到虾蟹养殖的日程上来。其中饲养的营养及配制、饲喂方法又成为虾蟹健康养殖中最主要的一环。实践证明,凡使用全价配合饲料进行养殖的虾蟹,都可收到良好的养殖效果。现将全价配合饲料在虾蟹养殖中的作用及相关使用技术分述如下： 一、全价配合饲料的概念及种类、类型 １．全价配合饲料的概念 全价配合饲料又称配合饲料。它是根据多种单一饲料原料所含的营养成份,按不同的饲养对象种类,不同的生长阶段,及生长能力,…     

一株嗜盐光合菌的分离及对养殖污水的处理效果

以海南虾池特殊生境底泥为菌源,富集、分离出一株嗜盐光合菌,命名HPSB2,并对其进行形态学观察、特征峰值测定及生理生化检测.结果显示:其与红环菌科(Rhodocychceae)索氏菌属(Thauera)特性相似,16SrDNA序列比对显示与Thauera aminoaromatica和Thauera mechemich...     

Water quality and plankton densities in mixed shrimp-mangrove forestry farming systems in Vietnam

Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimp‐mangrove forestry farms in Ca Mau province, southern Vietnam, to detail basic water chemistry and assess whether conditions are suitable for shrimp culture. In general, water quality was not optimal for shrimp culture. In particular, ponds were shallow (mean ± 1SE, 50.5 ± 2.8 cm), acidic (pH < 6.5), had high suspended solids (0.3 ± 0.03 g l^?1), low chlorophyll a/phytoplankton concentrations (0.2 ± 0.05 µg l^?1 and 8600 ± 800 cells l^?1 respectively) and low dissolved oxygen (DO) levels (3.7 ± 0.15 mg l^?1). Eight out of the 12 farms sampled had potentially acid sulphate soils (pH < 4.2). Salinity, DO and pH were highly variable over short time‐periods (hours); DO in particular was reduced to potentially lethal levels (1–2 mg l^?1). Seasonal variations in water chemistry and plankton communities (i.e. salinity, DO, phosphate, temperature, phytoplankton and zooplankton densities) appear to be driven by differences in rainfall patterns. The presence or absence of mangroves on internal pond levees (‘mixed’ versus ‘separate’ farms) and the source of pond water (rivers versus canals) were of lesser importance in determining water quality patterns and plankton biomass. Zooplankton and macrobenthos densities were sufficient to support the current (low) stocking densities of shrimp. However, natural food sources are not adequate to support increases in production by stocking hatchery reared post larvae. Increasing productivity by fertilization and/or supplemental feeding has the potential for adverse water quality and would require improvements to water management practices. Some practical strategies for improving water quality and plankton densities are outlined.     

Impact of farming intensity and water management on nitrogen dynamics in intensive pond culture: a mathematical model applied to Thai commercial shrimp farms

A mathematical model is used to investigate the impact of farming intensity and water management on nitrogen dynamics in the water column of intensive aquaculture ponds. The model describes the input of ammonia, its assimilation by phytoplankton or nitrification, and the loss of nitrogen through sedimentation, volatilization, and discharge. The model is calibrated for two commercial shrimp (Penaeus monodon Fabricius) farms in Thailand. Assimilation by phytoplankton with subsequent sedimentation or discharge is the principal process of ammonia removal. When inputs of ammonia exceed the algal assimilation capacity (carrying capacity), nitrification and volatilization of excess ammonia become significant. Carrying capacity is negatively affected by non-chlorophyll turbidity, and was estimated as 6 t ha^?1 cycle^?1 at a non-chlorophyll extinction of 2.6 m^?1. In ponds managed within their carrying capacity, ammonia concentrations are lowest at no water exchange, reach a maximum at exchange rates between 0.2 and 0.4 day^?1, and decline again at higher rates. When the carrying capacity is exceeded, excess ammonia concentrations decline continuously with increasing water exchange. Average exchange rates used in intensive shrimp farms (up to 0.2 day^?1) reduce phytoplankton abundance and sedimentation within ponds, but not ammonia concentrations. Discharges are high in particulate nitrogen at water exchange rates up to 0.3 day^?1, but contain mainly dissolved nitrogen at higher rates.     

Effect of combined shrimp and rice farming on water and soil quality in Bangladesh

This study analyzed water and soil quality and environmental impacts of shrimp farming in the southwestern coastal region of Bangladesh. Shrimp farming in the region is very traditional in nature where two culture systems viz. shrimp–rice and shrimp-only are being practiced, which are characterized by lower production, repeated stocking, irregular feeding, and fertilizing. Water quality in both farming systems was found suitable for optimum growth and survival of shrimp (Penaeus spp.). The level of 5-day biological oxygen demand (BOD₅) in both systems even in canal water was within the recommended level provided by the Government of Bangladesh which is less than 5 mg/l. Therefore, effluents of shrimp farms in the study area did not show any nutrient pollution on the surrounding environment. However, saltwater intrusion has caused many problems like loss of agricultural production, reduced availability of fodder for livestock, and fresh water for domestic uses in the coastal region. The findings of this study confirmed that shrimp farming using saline water have long-term effect of soil salinization. As a result, it poses a real threat toward sustainability of coastal shrimp farming as well as coastal development in Bangladesh.     

Transaction costs in contract farming models for mussel and oyster farming in South Africa: Organisational and management implications

Abstract

This study examines transaction costs faced by small mussel and oyster growers to elicit the appropriate organisational design of contract institutions. The theoretical premise is that high transaction costs essentially constrain the participation of small growers in mussel and oyster mariculture. Transaction cost analysis is applied to contract farming models and this approach is first discussed conceptually. Experience with contract farming by small growers in a developing context is synthesised and used in guiding the design of contract farming models. This is followed by a brief overview of the mussel and oyster industries, which is used to gain insight into transaction costs associated with contract institutions. Contracting models and implications are assessed separately for each industry. For mussel mariculture, four farming models are examined and the appropriate model is subsequently selected. For oyster mariculture, the transaction costs of contract fanning are examined to assist in organisational design.     

Diagnosis and management of small-scale fisheries in developing countries

Small‐scale fisheries (SSF) make important but undervalued contributions to the economies of some of the world’s poorest countries. They also provide much of the animal protein needed by societies in which food security remains a pressing issue. Assessment and management of these fisheries is usually inadequate or absent and they continue to fall short of their potential as engines for development and social change. In this study, we bring together existing theory and methods to suggest a general scheme for diagnosing and managing SSF. This approach can be adapted to accommodate the diversity of these fisheries in the developing world. Many threats and solutions to the problems that beset SSF come from outside the domain of the fishery. Significant improvements in prospects for fisheries will require major changes in societal priorities and values, with consequent improvements in policy and governance. Changes in development policy and science reflect these imperatives but there remains a need for intra‐sectoral management that builds resilience and reduces vulnerability to those forces beyond the influence of small‐scale fishers.     

Using residual water from a marine shrimp farming BFT system. part I: nutrient removal and marine microalgae biomass production

Microalgae have great biotechnological potential but the high cost of traditional formulae culture media is one of the limiting factors to their commercial cultivation. As an alternative, the use of residual water from other activities has been proposed as a culture medium. The goal of this study was to produce Chaetoceros muelleri, Nannochloropsis oculata and Tetraselmis chuii biomass using residual water from an intensive Litopenaeus vannamei biofloc cultivation system and to verify the ammoniacal nitrogen, nitrite, nitrate and orthophosphate consumption. The microalgae cultures were developed until the second day of their stationary phase in the following treatments: 100% f/2 culture media; 100% residual water; residual water diluted 50% with marine water. T. chuii and N. oculata presented the best relative biomass average (576 mg L^?1; 474 mg L^?1)(P > 0.05). All the species completely assimilated the orthophosphate in 2 days. In 10 days, T. chuii and N. oculata assimilated 87% and 85% of nitrate respectively. It can be concluded that residual water from an L. vannamei biofloc cultivation system can be used as an alternative culture medium for T. chuii and N. oculata biomass production. Moreover, the microalgae biomass proved to be very effective in recycling the dissolved nutritive salts.     

对虾养殖中的清塘及养殖期间水体消毒药物使用的探讨

养虾池塘的塘底和养殖水体常因环境变异而滋生细菌,病毒以及附生物,导致虾病发生。养殖对虾放养前的清塘及养殖过程中的水体消毒,是关系到养虾成功或失败的一项重要工作。常用于清塘和消毒的药物十几种。放养前清塘常用的有生石灰、茶麸、敌百虫、强氯精等药物。养殖期间常用的有生石灰、强氯精、二氧化氯,高锰酸钾、新洁尔灭等药物。 本文只就养虾过程中的放养前清塘及放养后的水体消毒使用药物问题作一些探讨。 一、他们及水体消毒的目的 在养虾池塘中,从大海进入的海水,会带进鱼类、甲壳类和各种原生动物、有害细菌及病毒。鱼类是…     

Forecasting weekly salmon prices: Risk management in fish farming

Abstract

Production of farmed salmon has increased substantially during the last decade. Most of the salmon production is sold spot, resulting in large price fluctuations both for the producer and for the exporter. No derivative markets exist; consequently, no one can hedge prices. If prices could be forecasted within reasonable confidence bounds, risk would be reduced. This study used six easily applicable procedures to forecast weekly producer prices for salmon. The procedures tested were Classical Additive Decomposition (CAD), Holt Winters Exponential Smoothing (HW), Auto Regressive Moving Average (ARMA), Vector Auto Regression (VAR) and two different naïve models: post‐sample predictive accuracy was evaluated. Results indicated that the CAD model forecasted the direction of price movements best, whereas the VAR model performed best according to accuracy measures.