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.     

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.     

Community livelihood and patterns of natural resources uses in the shrimp‐farm impacted Mekong Delta

This case study looks at changing livelihood strategies of the coastal population in Soc Trang Province in the Mekong Delta, Vietnam, and their impacts on natural resources. It provides an opportunity not only to document the impact of shrimp farming on coastal livelihood but also to better understand the link between brackish water aquaculture development and natural resource use. The approach includes a socio‐economic survey in six villages of the province focusing on risk strategies and livelihood diversification. Shrimp farming was found to be less risky and more profitable for households and private companies with a higher investment capacity than for poorer households. Households facing a high risk in shrimp farming diversified their aquaculture production, with other high‐value species like mud crab and elongated goby as a coping mechanism. The use of natural resources' collection is shifting from home consumption towards market‐oriented sales of juvenile mud crabs, clams or fish (elongated goby) to supply seed for brackish water aquaculture developments.     

Production Methods and Resource Use at Litopenaeus vannamei and Penaeus monodon Farms in India Compared with Previous Findings from Thailand and Vietnam

Shrimp farms in India had average yields (pond surface basis) of 7.86 ± 1.04 (SE) m.t./ha/yr for Litopenaeus vannamei (n = 89) and 3.88 m.t./ha/yr for Penaeus monodon (n = 11). Average feed conversion ratio was 1.48 ± 0.04 for L. vannamei and 1.24 ± 0.12 for P. monodon. Land use for production ponds, supporting area, and feed ingredients averaged 0.634 ± 0.053 ha/m.t. for L. vannamei and 0.716 ± 0.087 ha/m.t. for P. monodon. Saline water volume used at farms without water exchange was 18,522 ± 4065 m³/m.t. for L. vannamei and 9528 m³/m.t. for P. monodon. Farms exchanging water used 149,188 m³/m.t. for L. vannamei and 191,500 m³/m.t. for P. monodon. Freshwater embodied in feed was 1678 ± 508 m³/m.t. for L. vannamei and 1401 ± 137 m³/m.t. for P. monodon. Average energy use for farm construction and repair, farm operations, and embodied in feed and liming materials was 82.14 ± 9.08 GJ/m.t. for L. vannamei and 59.03 ± 24.92 GJ/m.t. for P. monodon. Wildfish used to make fishmeal included in feed was 1209 kg/m.t. for L. vannamei and 1611 kg/m.t. for P. monodon. Farm infrastructure, pond management methods, yields, and resource use in India were similar to those previously reported for shrimp farms in Thailand and Vietnam.     

Aquaculture and poverty alleviation in Ben Tre Province,Vietnam

Research results on the effects of aquaculture on poverty alleviation have been mixed. We use Tobit, simulation models and cross sectional survey data of 285 households, in Ben Tre Province, Vietnam, to evaluate the effects of aquaculture involvement on poverty, measured using per capita consumption of less than $1.25 USD, $1.50, and $2.00 per day. The results show for per capita consumption of less than $1.25 per day that households’ aquaculture participation or productivity had no or little effect on the living standard. For income levels above $1.25 per capita per day aquaculture participation or productivity influenced the standard of living.     

ECONOMIC RISK ASSESSMENT OF A SEMI-INTENSIVE SHRIMP FARM IN SINALOA,MEXICO

In Mexico shrimp farming is the most important aquaculture activity. However, its sustainable development has been threatened in recent years by the economic risk associated with low yields caused by outbreaks of viral diseases. A stochastic bioeconomic model was developed to analyze the economics of farm management adjustments as a response to disease risks, using pond-level data from a farm operating in the State of Sinaloa, Mexico, during the period 2001–2005. The data base analyzed included different combinations of stocking density (in the range 6–30 PL/m²) and culture time (from 12 to 31 weeks), which allows for wider application of the simulation results, even at the industry level. Results from this study indicate that operating costs would increase by 33% if the farmer would choose to market product directly. Scenarios with lower stocking densities and intermediate culture times generated the highest probabilities 6–9 PL/m² 16–19 weeks (76%/100%/70%), and 10–14 PL/m² 20–24 weeks (72%/99%) of achieving superior economic performance, as demonstrated by achieving the target reference point of 35% operating profit margin ratio. The study reinforces the value of the current trends in Sinaloa to reduce stocking density as a good management practice to decrease the impact of diseases. This study also provides important additional knowledge on the specific economic results and risks associated with the combination of these two management variables at different levels.     

柘林湾沿岸对虾养殖环境的氮磷负荷与区域分布

研究了柘林湾沿岸对虾养殖产生的环境氮磷负荷及其来源的数量和比例.2006年柘林湾沿岸对虾养殖产生的环境氮负荷为210.21 t,其中来源于对虾的排泄氮、粪氮和残饵氮分别为157.10 t、39.61 t和13.50 t;环境磷负荷为45.45 t,其中排泄磷、粪磷和残饵磷分别为4.93 t、24.87 t和15.65 t.对虾养殖环境氮负荷主要来源于对虾的排泄,占氮负荷的74.74%,而磷负荷主要源自粪便,占磷负荷的54.72%.柘林湾沿岸对虾养殖的环境氮磷负荷量以湾北部沿岸最大,北部、西部和东部沿岸环境氮负荷分别为144.86 t、53.99 t和11.36 t,环境磷负荷分别为31.32 t、11.68 t和2.46 t.     

中国对虾产业现状及相关研究综述

中国对虾产业在国际上具有重要地位,但近年来中国对虾出口形势面临从未有过的巨大挑战,因此,了解我国对虾产品、产业的现状,加大我国对虾产品与产业的研究,对我国对虾产业增强竞争能力和可持续发展具有一定意义。     

柘林湾沿岸对虾养殖环境的氮磷负荷与区域分布

研究了柘林湾沿岸对虾养殖产生的环境氮磷负荷及其来源的数量和比例。2006年柘林湾沿岸对虾养殖产生的环境氮负荷为210.21t,其中来源于对虾的排泄氮、粪氮和残饵氮分别为157.10t、39.61t和13.50t;环境磷负荷为45.45t,其中排泄磷、粪磷和残饵磷分别为4.93t、24.87t和15.65t。对虾养殖环境氮负荷主要来源于对虾的排泄,占氮负荷的74.74%,而磷负荷主要源自粪便,占磷负荷的54.72%。柘林湾沿岸对虾养殖的环境氮磷负荷量以湾北部沿岸最大,北部、西部和东部沿岸环境氮负荷分别为144.86t、53.99t和11.36t,环境磷负荷分别为31.32t、11.68t和2.46t。     

Economic Optimization of Shrimp Farming in Honduras

A profit-maximizing linear programming model with a risk programming component was developed to identify sets of optimal management strategies and outline an annual schedule of production activities for shrimp farming in Honduras. A database of 912 complete pond production records was used to define technical relationships between stocking density and survival and growth rates and to develop net return coefficients for the mathematical model. Separate matrices were developed for three farm-size scenarios to account for economies of scale. Results indicated that, in spite of recent viral epizootics, shrimp farming continues to be a profitable economic activity. Stocking density was found to have a negative effect on growth rate, but not on survival rate. As a consequence, low and intermediate stocking rates were most commonly selected, but high stocking densities were recommended in certain periods of the dry season. Results demonstrated some economic advantages of reducing the traditional levels of water exchange with supplemental aeration. The risk programming analysis indicated that the selection of low and intermediate stocking rates resulted in overall annual risk levels that were relatively low.     

Fatty Acid Profiles of Different Shrimp Species: Effects of Depth of Catching

The aim of this study was to investigate fatty acid profiles of different shrimp species caught from deep water and shallow water. The shrimp species investigated in the study were Aristeus antennatus, Aristeomorpha foliacea, Plesionica martia, Parapenaeus longirostris, and Plesionica edwardsi from deep water; and Metapenaeus monoceros, Penaeus semisulcatus, Penaeus kerathurus, and Penaeus japonicus from shallow water.

Fatty acid composition of shrimps varied. The main fatty acids were C18:1n9, C16:0, C25:6n3, C22:5n3, and C18:0. Saturated, monounsaturated, and polyunsaturated fatty acid (PUFA) contents of P. longirostris, P. edwardsi, and M. monoceros were markedly different, respectively. The ratio of n6/n3 of the edible tissue of M. monoceros was found to be 0.795, whereas this value was 0.152 in A. foliacea. Among the species studied, the highest docosahexaenoic acid + eicosapentaenoic acid value was found for P. kerathurus. The levels of PUFAs of shallow water shrimps (ranging from 33.44 to 42.77%) were found to be higher than those of deep water shrimps (ranging from 29.68 to 33.95%). Marine animals in the upper water layers gain nutrition through phytoplankton which provides n-3 PUFA depending on solar energy. Shallow water shrimp species provide a satisfying amount of PUFA.     

虾池水环境因子与虾病爆发的相关性分析

2001～2002年在对瓦房店市和庄河市等虾池水环境因子的连续监测中,运用多元分析研究了水环境因子与对虾病害爆发的相关性,主成分分析结果表明,NO3-N、COD、NO2-N、盐度、NH3-N和水温是显示对虾疾病爆发的关键因子。     

跑道式南美白对虾养殖池中弧菌的数量动态

采用TCBS平板计数法对南美白对虾跑道式养殖池和土塘养殖塘水样弧菌数量进行了一个养殖周期的连续监测。结果表明:跑道式养殖池水体中弧菌数在放苗后的前70 d均较低,随后迅速增加并维持在一个较高水平,变化幅度为15.0~1.42×104cfu/ml,平均3.96×103cfu/ml,平均数比土塘高2倍。跑道式养殖对虾始终未发病,跑道式养虾病害少,产量高。     

湖泊网围养鱼不同放养结构的研究

本试验分3年进行,在3个667平方米的网围内采取主养草鱼(草鱼占草食性鱼类80％),主养团头鲂(团头鲂占80％)和草鱼、团头鲂并重(草鱼、团头鲂各占50％)的三种放养结构;每个网围第1年放草食性鱼种50公斤,第二年放种100公斤,第三年放种150公斤,以比较其养殖效益。经三年试验,其产量、增重倍数、产值、投入产出比:放养草食性鱼种50公斤时,草鱼、团头鲂并重的放养结构的四项指标最佳,分别为281.7公斤、4.8、1890.2元、1:1.33;放种量100公斤时,主养团头鲂的放养结构的四项指标最佳,分别为551.4公斤、4.8、3740.6元、1:1.74;放种量150公斤时,主养团头鲂的养殖结构的四项指标最佳,分别为795公斤、4.9、5460元、1:1.79。四项指标以放种量在100公斤和150公斤时为最佳。因此,浅水草型湖泊在进行小块网围精养时,以采用主养团头鲂或团头鲂、草鱼并重,放养量100～150公斤的结构为好。     

投加微生物制剂对对虾养殖池总氨氮与亚硝酸氮的影响

监测并分析了单独或组合加入光合细菌、益生菌(酵母与乳杆菌)和芽孢杆菌后,对虾养殖池凌晨水体中氨氮和亚硝酸氮的变化。试验分为6组,即3个单独添加组(益生菌组、芽孢杆菌组、光合细菌组)和3个组合添加组(光合细菌与芽孢杆菌组、益生菌与芽孢杆菌组、光合细菌与益生菌组)。结果表明,添加微生物制剂后,益生菌组、芽孢杆菌组、光合细菌与芽孢杆菌组、益生菌与芽孢杆菌组池塘水体中总氨氮水平提高了41%~99.8%;而光合细菌组、光合细菌与益生菌组无显著性变化,但亚硝酸氮水平有所升高(107%~210%)。单独添加组水体中总氨氮水平的变化强弱顺序为芽孢杆菌>益生菌>光合细菌,组合添加组为芽孢杆菌与益生菌组>芽孢杆菌与光合细菌组>益生菌与光合细菌组。试验期间各组养殖池中总氨氮浓度为0.51~1.94 mg/L、亚硝酸氮水平为0.016~0.096 mg/L,均在安全浓度以下,说明添加微生物制剂未引起池塘氨氮和亚硝酸氮的毒性问题。     

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.     

The Effects of Air Exposure on Hemolymph Osmoregulatory Capacity of Brown Tiger Shrimp,Penaeus esculentus,and Western King Shrimp,Penaeus latisulcatus,Reared at Different Salinities

Abstract

Hemolymph osmolality and osmoregulatory capacity (OC) of brown tiger shrimp, Penaeus esculentus (0.94±0.04 g mean initial weight) and western king shrimp, P. latisulcatus (5.37±0.10 g mean initial weight) from four salinities (10, 22, 34 and 46 ppt) were determined following 7, 14 and 21 minutes of air-exposure. Hemolymph osmolality of both species increased with increasing salinity. Isosmotic points of brown tiger shrimp calculated from regression lines between hemolymph and medium osmolality were 30.9, 31.9, 32.1 and 31.1 ppt at 0, 7, 14, and 21 minutes of air-exposure, respectively. Isosmotic points of western king shrimp were 33.8, 33.3, 32.8 and 33.1 ppt at 0, 7, 14, and 21 minutes air-exposure, respectively. OC of brown tiger shrimp at salinity of 34 ppt did not change when exposed to air for any length whereas OC of shrimp at other salinities (10, 22 and 46 ppt) were significantly different (P < 0.05) when exposed to air for 21 minutes. OC of western king shrimp at salinity 10 ppt was reduced (P < 0.05) when exposed to 14 and 21 minutes of air when compared to control and 7 minutes of air exposure. The results indicate that both species spent less energy (P < 0.5) for osmoregulation from 30 to 34 ppt. Furthermore, salinities 10 and 46 ppt were unsuitable for rearing brown tiger shrimp and salinity 10 ppt was unsuitable for growing western king shrimp.     

对虾工厂化养殖的系统结构

对虾工厂化养殖是在人工控制条件下,利用有限水体进行对虾高密度养殖的一种生产方式,它依托一定的养殖工程和水处理设施作为技术支撑,融合无公害生产的管理模式,是一种高效的环境友好型养殖。文章就构建对虾工厂化养殖平台中的各系统环节及该种生产模式的概况作系统综述。     

液态氧在对虾工厂化养殖中的增氧效果

试验结果表明,液态氧能使养殖水体持续维持较高的溶解氧(DO)含量(充气压力0.15 MPa,DO≥7.0 mg/L),且分布均匀,无DO分层现象.成本分析表明,液态氧增氧的成本略低于动力增氧.