鲆鲽类苗种技术创新与推广对策——基于生产者技术需求调研的思考

苗种是水产养殖生产的基础资料,苗种科技创新与推广的有效程度直接影响到产业可持续发展。以作为我国海水鱼类代表的鲆鲽类养殖业为例,基于养殖生产者的技术需求调研结果,提出了该产业苗种技术创新与推广的策略,即以市场为导向,始终将苗种科技创新作为重要的产业发展战略;密切结合产业发展转型战略,有效对接产业差别化需求,有差别地重点推进快速生长苗种、强抗逆性苗种以及全雌化优质苗种的培育与推广;因地制宜推进特色品种苗种培育,为塑造区域性鲆鲽类产品品牌提供支撑;认真做好战略储备性品种的苗种培育,切实推进产业的梯度发展;密切关注我国近海渔业资源修复之需求,培育适于增殖放流的鲆鲽类苗种。     

The Potential and Sustainability of Aquaculture in India

ABSTRACT

India is a very populous country with more than one billion people. In order to provide food for this growing population, serious environmental problems may result. Despite many benefits from the green, blue, and silver revolutions adopted in India, there has been much concern resulting from intensive agricultural practices that led to environmental problems in both terrestrial and aquatic ecosystems. Increasing demand for aquatic resources also caused inland fisheries to decrease over the past few decades. The location of aquaculture projects, landscape destruction, soil and water pollution by pond effluents, over-exploitation of important fish stocks, depletion in biodiversity, conflicts over agriculture and aquaculture among various stakeholder groups over resource and space allocation, and international fish trade controversies have threatened the long-term sustainability of fisheries and aquaculture industries. The subject of sustainable aquaculture has not been adequately projected in terms of current aquaculture practices aimed to boost a rural economy. This review briefly describes the key issues of aquaculture unsustainability in terms of intensive aquaculture, nutrient enrichment syndrome, soil and groundwater salinization, destruction of mangroves, loss of biodiversity, marine pollution and loss of fish stock, use of aquachemicals and therapeutics, hormone residues, etc. The strategies for sustainability have been highlighted with respect to rice-cum-fish culture, carp polyculture, integrated farming with livestock, rural aquaculture, intensification of small farms, wastewater-fed aquaculture, crop rotation, probiotics, feed quality, socioeconomic considerations, environmental regulations and fisheries acts, transboundary aquatic ecosystems, impact of alien species, ethical aspects of intensive aquaculture, responsible fisheries, and environmental impact assessment. A suggested model outlines the feedback mechanisms for achieving long-term sustainability through improved farm management practices, integrated farming, use of selective aquachemicals and probiotics, conservation of natural resources, regulatory mechanism, and policy instruments.     

GEOGRAPHICAL DISTRIBUTION OF INVESTMENT IN SMALL-SCALE RURAL FISH PONDS

This article provides a detailed empirical study of investment patterns in small-scale rural aquaculture and its relation to pond location based on a systematic fish pond survey in Lao PDR. Nominal investment categories of fish ponds were created based on stocking rate, feed and water and then spatially cross-referenced with a range of environmental factors, including distance to roads, land use, and distance to water resources. Contrary to current aquaculture development policies, the results show the dynamic nature of fish ponds as a source of water, native fish and exotic fish. It is concluded that policy makers and extension officers can make use of simple diagnostic models of fish pond use and investment to develop more contingent support to farmers that takes into consideration a wider portfolio of living aquatic resources in rural communities.     

The profitability of producing channel catfish Ictalurus punctatus (Rafinesque) in cages at a commercial scale on small farms

Past beneficiaries of research and extension projects in aquaculture in the USA have been large farmers using pond culture systems. Additional studies, based on sound knowledge of empirical behaviour, are needed to identify alternative technologies and aid in the management decisions of small-scale farms. A mixed integer, multiperiod linear programming model and survey data were used to analyse the profitability of caged channel catfish, Ictalurus punctatus (Rafinesque), culture. Results suggest that only a limited number of farmers may be able to adopt cage culture as an alternative farm enterprise. Profitability was sensitive to assumed product prices.     

Economic Analysis of Nile Tilapia (Oreochromis niloticus) Production in Tanzania

In Tanzania, Nile tilapia culture is a promising aquaculture enterprise. Information on production costs could assist fish farmers in economic and financial planning. Economic profitability of small‐scale Nile tilapia production in Tanzania is analyzed using a model that simulates individual fish growth and takes into account fish population dynamics in the pond. The results suggest that the current practiced mixed‐sex tilapia culture without predation is not economically sustainable. Extension efforts should be geared toward developing a Nile tilapia production system that is based on a hand‐sexed all‐male tilapia. Meanwhile catfish can be introduced in ponds to control overcrowding in mixed‐sex tilapia culture without predation. Studies to determine optimal pond sizes, availability of feed, and a quality fingerling supply chain are also fundamental for developing a sustainable Nile tilapia production system in Tanzania. Under improved Nile tilapia production systems, returns are high enough to justify investment through borrowed capital from formal institutions.     

Analysis of the use of credit facilities by small-scale fish farmers in Kenya

The government of Kenya encourages aquaculture development by offering credit facilities through the government agricultural finance institution, Agriculture Finance Corporation. Nevertheless, the level of credit use in fish farming is very low. Access to credit is among several factors that affect farmers’ decision of whether to use particular technology or services. The study examined factors that affected the decision of fish farmers in Kenya to utilize credit facilities in fish production using a probit model. The analysis suggests that farmers in the Western province will have a 19% more probability of using credit facilities for their fish farming operations than farmers from the other provinces such as the Rift Valley, Central, and the Eastern province. The effect of tilapia sales on the probability of credit use by fish farmers is more than three times that of catfish sales. Total pond acreage owned by fish farmers had a positive effect on credit use but the effect was very small and negligible. The level of fish farmers’ use of credit facilities is very low, and there is probably the need to educate farmers on credit use and for the government agricultural lending agency and other commercial agricultural lenders to invest in this enterprise. Kenyan lending institutions have financed traditional agricultural enterprises, and with the growing production of farmed fish, more research is needed to document the aquaculture business model to assist in assessing the profitability potential in aquaculture.     

Technical efficiency of carp production in Nepal: An application of stochastic frontier production function approach*

Abstract

Modern aquaculture is a relatively new activity among Nepalese farmers and a small contributor to the economy. Given the abundance of water resources and fish species, rising demand for fish, and its high profitability, aquaculture has potential for future expansion if it is given appropriate attention from the government. In Nepal, productivity in aquaculture is much lower compared to other countries in the region, which suggests that there is potential for increased fish production through technological progress and improvement in farm‐level technical efficiency. However, no formal analysis has yet been conducted to assess the productive performance of Nepalese aquaculture and its potential for future improvement. Against this background, this paper examines the technical efficiency and its determinants for a sample of fish pond farms from the Tarai region of the country using a stochastic production frontier involving a model for technical inefficiency effects. The estimated mean technical efficiency is 77%, with intensive farms being more efficient than extensive farms. The adoption of regular fish, water, and feed management activities has a strong positive effect on technical efficiency.     

An assessment of alternative strategies for the integration of pond aquaculture into the small‐scale farming system of North‐east Thailand

Abstract

This paper uses a linear programming model to examine the economic viability of four fish production strategies in the context of rainfed farming systems in the north‐eastern region of Thailand. The four systems are rice bran feeding system, pond fertilization using buffalo manure, fish production recommendations developed by the Asian Institute of Technology (AIT) Recommendations and an integrated duck/fish production system. These systems have been introduced into North‐eastern Thailand where the main obstacles to fish production are the lack of indigenous knowledge offish culture and a shortage of water. While technical feasibility studies are needed to evaluate the practical viability of aquaculture technologies, economic assessment is required to assess their commercial viability. The objective of this paper is to examine whether or not these fish production systems can contribute to, and integrate with, the prevailing farm system in the North‐east of Thailand. The linear programming model is used to determine the optimum on farm product mix that maximizes net returns under each of the four production systems. Among different resources, labour requirement in the fish‐stocking month appeared to be the first binding resource, while capital requirement was not a constraint for an average farming household of the region. A sensitivity analysis is presented to show how each of the fish production systems operates with different levels of pond size, labour and capital availability. The results of the study show that these aquaculture systems are economically attractive and can contribute significantly to the livelihood of the small‐scale farmers of North‐east Thailand.     

Aquaculture information sources for small-scale fish farmers: the case of Ghana

The Ghana ministry of fisheries and the ministry of Agriculture provide free extension services and other technical services to fish farmers in Ghana, e.g. producing fingerlings at government-operated fish hatcheries for sale to farmers. Non-governmental organizations and universities have also provided some technical assistance to fish farmers in efforts towards the development of aquaculture in Ghana. The study identified the various sources of aquaculture information to Ghanaian fish farmers and examined the factors that affected their decision to utilize these alternative sources of information. Using choice modelling techniques, the study found that the probability of farmers seeking information on aquaculture from the Ghana government increases with literacy by about 43% more than with illiteracy and by about 34% with an increase in total size of ponds. The probability that a literate farmer will choose to obtain aquaculture information from a non-governmental organization decreased by about 10% compared with an illiterate farmer. The probability of choosing 'other sources' for aquaculture information increased by about 27% for farmers residing in Ashanti region compared with farmers in the Brong-Ahafo region but the probability of farmers seeking information from 'other sources' decreased with literacy and number of years farming.     

Effects of modified pond management on limnological parameters in small‐scale aquaculture ponds in mountainous Northern Vietnam

In mountainous Northern Vietnam, traditional pond aquaculture is part of the integrated farming activity contributing to food safety and to income generation for small‐scale farmers of ethnic minorities. Traditional pond management consists of a polyculture of macro‐herbivorous grass carp with 3–5 other fish species that are cultured in small ponds with constant water flow through. The main limitations to production are species‐specific mass mortalities of grass carp, a poor feed base especially for all species but grass carp, and poor water quality. In this study, we compared the traditional pond management to a semi‐intensive pond management that was based on the traditional management system but included changes designed by researchers to increase fish production. The modifications consisted of water inflow control, supplemental fertilization and feeding, and a polyculture dominated by common carp. The changes in management significantly reduced the turbidity and increased oxygen supply, as well as the natural food base within the pond. These changes in pond management provide farmers with the possibility to improve their pond aquaculture scheme and overcome previous limitations.     

Seasonal dynamics of fish assemblage in a pond canal

The annual dynamics of fish assemblage in a pond-connecting canal of a South Moravian pond aquaculture facility was studied to reveal potential assemblage effects on pond stocks and vice versa. The species richness of fish assemblage and seasonal dynamics of its development were predominantly dependent upon the fish stock of the interconnected ponds (particularly due to escapees during the period of pond harvesting), which contributed to a considerable increase of commercial fish species occurrence. Using a seasonal parameter, the season proved to have a major impact on fish assemblage dynamics (r = −0.71, P < 0.001). Spring samples were dominated by commercial fishes of aquaculture origin (mainly Cyprinus carpio). Occurrence of several fish species originating from the wild (bleak, Alburnus alburnus, chub, Leuciscus cephalus and roach, Rutilus rutilus) was also reported. The pond canal was found to be an important reservoir site of persistent survival and potential subsequent spreading of some undesirable alien fishes such as topmouth gudgeon (Pseudorasbora parva) and gibel carp (Carrasius auratus). Moreover, more attention should be paid to the potential negative impacts of all fishes of aquaculture origin upon the natural ecosystem and to the adverse effects due to the immigration of wild fish into aquaculture pond farming units.     

鲆鲽类养殖技术需求分析

通过对鲆鲽类主产区养殖户进行抽样调查,分析养殖户所关心的技术问题,包括海水资源利用、鱼苗、鱼药和饲料等关键投入要素,分析了产生这些问题的原因。在统计分析的基础上,进一步阐明了政府部门、科研单位、企业和行业协会在解决相关问题时应该参与的程度,最后提出相关政策建议。     

Fish culture in rainfed rice fields of northeast Thailand

Adoption of rice-fish culture by farmers in the rainfed areas of northeast Thailand is examined with reference to recent field research and extension in the region. The practice is placed in perspective with the development of aquaculture per se and the human and agricultural ecology of this heterogeneous region. Rice-fish culture is a recent activity in the region and has been promoted by government and non-government agencies with variable success among small-scale farmers. The widespread availability of private hatchery-produced fish seed and perceived decline in wild fish have been important stimuli. Rainfed rice fields are marginal agricultural environments and lack of water constrains both rice and fish production. Wild swamp fish are tolerant of these conditions and traditional systems for their management and capture have expanded greatly in recent years. In much of the region ‘trap’ ponds are used more for catching wild fish than as refuge sumps or ponds for fish culture per se; wild fish typically constitute between 20 and 80% of the total yields in stocked systems. Widespread availability of fish seed allows more farmers to try rice-fish culture but the small size of seed at purchase is still a problem particularly where carnivorous, wild fish are prevalent. Appropriate on-farm nursery techniques may improve success and adoption of hapa nursing has been high in some parts of the region. Species ratio and density of fish stocked depends mainly on their availability from fry traders; the major species stocked in rice fields are the silver barb (Puntius gonionotus), common carp (Cyprinus carpio) and Nile tilapia (Oreochromis niloticus).

Farmers adapt rice fields for fish culture as part of their whole farm strategy; benefits to rice, vegetable and fruit and livestock may be considered more important than fish yields. The high value attached to even small quantities of fresh fish is a major incentive for rice-fish culture, but women who are decision makers in terms of changes to rice fields and household consumption have often not been fully considered during promotion of rice-fish.

The relatively small areas of riceland that farmers can stock and harvest fish, low yields per unit area and high consumption of fish reduces the importance of rice-fish culture in many rural households. The analysis suggests that stocking fish in rice fields in areas with poor access to wild fish supplies from community water bodies would have most impact.

Although rice-fish culture can contribute to subsistence requirements, the high labour demand often means that intensified capture of wild fish or pond-based culture of fish are more attractive for poorer and better off farmers, respectively.     

Effects of silver carp and the small indigenous fish mola Amblypharyngodon mola and punti Puntius sophore on fish polyculture production

A sustainable semi-intensive pond aquaculture technology including major carp species as cash-crop and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. The inclusion of silver carp (Hypophthalmichthys molitrix), a cheap large species affordable by poor farmers, is now being considered. As part of a study on the effects of this filter feeder on polycultures including the large carps rohu (Labeo rohita), catla (Catla catla) and common carp (Cyprinus carpio) and the SIS punti (Puntius sophore) and mola (Amblypharyngodon mola), an experiment was carried out under farm conditions to test the effects of silver carp and of each SIS species on the growth, survival and yield of the large and small species and on pond ecology.The experiment was performed in 38 farmers' fishponds of different sizes, from 220 m² to 1200 m². The results show that the larger the fish pond the better rohu performance, the larger punti fry weight and the lower punti fry harvested biomass. Pond size did not affect other fish species. The addition of 250 mola and/or punti per 100 m² fishponds affected rohu and catla and did not affect common and silver carps. The addition of mola alone reduced rohu's parameters by 15%. The addition of SIS in the three combinations tested (250 mola, 250 punti, 125 of each species) reduced catla's parameters by 20-24%. Punti fry were larger when both SIS were stocked and punti fry biomass was larger when only punti were present. Total mola harvested biomass and yield were larger when the entire SIS stocked were only mola.The addition of 10 silver carp over the 99 large carps stocked per 100 m² fishponds negatively affected rohu and catla growth and yield by about 15-21% and 45-50% respectively but not their survival, did not affect common carp performance, did not affect punti and mola reproduction in the ponds, reduced punti yields by 25%, reduced mola performance by about 35%, and silver carp own biomass increased total yield and total income in about 12% each. These effects are explained and discussed considering fish interactions through the food web. The decreased income from selling the more expensive large carps is more than compensated by that obtained from silver carp, which allows the option to the farmer to sell part of the silver carp to complete the cash income that would have been obtained from large carps only if silver carp would not be stocked, and consume the rest with the family.     

Fathead minnow reproduction: Implications for commercial culture

The fathead minnow, Pimephales promelas, is widely used as a bait, forage, and research fish in the United States. A hardy and fecund fish, this species has many attributes that are excellent for culture. Unfortunately, despite the widespread use of fathead minnows in toxicity testing and thousands of resulting publications, relatively little aquaculture‐related research has been conducted in support of commercial production. On the surface, current commercial fathead minnow production practices appear much the same as those of a decade ago. However, producers continue to refine culture methods, balancing broodfish stocking rates, spawning substrate quantity, and feeding rates in an attempt to meet both losses to predators and market demand. This review examines relevant reproduction‐related studies in the fields of ecology, behavior, toxicology, and aquaculture with the goal of advancing fathead minnow culture. In fathead minnow production, relative to the culture of food fish species, reproduction is vital, more so than rapid growth or a low feed conversion ratio. Fish numbers may exceed 1 million fish/ha, while feeding rates are relatively low and in feeder fish production, growth is deliberately restrained in order to maintain fish within market sizes year‐round. Underappreciated factors identified as affecting reproduction and with implications for commercial culture include: (a) poor egg adhesion to commonly used spawning substrates, (b) egg and fry cannibalism at high fish densities, and (c) the relatively short breeding period of individual males. Results highlight the importance of selecting an appropriate broodfish stocking rate based on fish size, anticipated pond fertility, and feeding program. New methods to improve reproductive performance will likely increase costs and will need to be accompanied by thorough economic analyses.     

Water use and conservation for inland aquaculture ponds

The general hydrological equation, inflow = outflow ± change in storage, can be used to make accurate estimates of water use by ponds for inland aquaculture projects. The primary inflows are precipitation, runoff and regulated water additions. The main outflows are evaporation, seepage, overflow after storms and intentional discharge. Water conservation measures such as maintaining storage capacity in ponds equal to the normal, maximum daily precipitation, reduction in seepage beneath dams and through pond bottoms, fish harvest without draining ponds, and water re-use are discussed. Even with the implementation of water conservation measures, pond aquaculture is a water- intensive endeavour which consumes more water per unit of area than irrigated agriculture. However, the value of aquacultural production per unit of water used greatly exceeds that of irrigated agriculture. Reduction in effluent volume is the most effective water saving means, and not only reduces water consumption but also reduces the pollution potential of pond aquaculture.     

黑鮶控光育苗技术研究

利用体重1～4kg的怀仔黑亲鱼56尾,完全人工控制弱光,长流水、自然水温培育,共产仔272万尾。布池后,根据不同日龄投喂轮虫、卤虫无节幼体、配饵和糠虾,控制光照,调节水质,防病治病,及时疏稀,420m~3水体育出平均全长28.8mm的黑苗77.6万尾,总成活率30％。认为,全人工控制光源蓄养亲鱼,溢水法布池,夜间开灯少量投饵,效果较好。     

Effect of Garlic,Echinacea, Organic Green and Vet-Yeast on Survival,Weight Gain,and Bacterial Challenge of Overwintered Nile Tilapia Fry (Orechromis niloticus)

The purpose of this study was to examine the effect of some immunostimulants and probiotics on the survival rate, final weight, and disease resistance of overwintered tilapia fry. There were five treatments: T1 (control) fed a balanced diet (35% protein) without additives. Treatments 2 to 5 were fed diets supplemented with 4% garlic, 4 g/kg Echinacea, 4 g/kg Organic Green or 4 g/kg Vet-Yeast, respectively. Growth and resistance to disease challenge with Aeromonas hydrophila and Pseudomonas flourescens were not different among treatments, but survival of overwintered fry increased in treatments fed probiotics or immunostimulents. The use of garlic in overwintering feeds could allow hatchery operators to increase their prices for fry and fish farmers to stock production ponds earlier, increasing hatchery revenues by 74% and improving land use efficiency and productivity for the Egyptian aquaculture industry.