Oxygenation for fish farms

This thesis provides a detailed study of methods for dissolving oxygen in water to reduce water requirements for fish farming. The principal sources of oxygen are air or pure oxygen gas. Aeration methods have the distinct advantage of the universal availability of air. However, the effectiveness of such methods is diminished by the presence of nitrogen in the air and, in general, the maintenance of dissolved oxygen levels above 70% saturation is likely to result in excessive power requirements. Pure oxygen has five times the solubility of oxygen in air and it is possible, therefore to achieve much higher transfer rates. However, oxygen is expensive and its economic use is essential: it is important, therefore, to dissolve a high proportion of the oxygen. Four distinct oxygenation systems were evaluated by the author. A detailed analysis of a column oxygenator is given first. The column was designed so that the oxygen bubbles generated are trapped within the column until dissolved. In seawater, much smaller bubbles are formed and this led to the development of a jet oxygenator which disperses gas rubbles within the rearing tank. Both the above systems were designed primarily for oxygenating recycled tank water. For oxygenating a primary water source, a U -tube device was evaluated. Lastly, the possibility of supporting fish stocks without any external power source, other than a pressured supply of oxygen from a liquid oxygen store, was considered. Experience of running commercial-scale oxygenation systems in high-intensity fish farms has made it possible to estimate operating costs of both aeration and oxygenation systems. The significance of these costs is discussed.

Projecting the fate of fish populations using ecological-economic modeling

Four marine fish species are among the most important on the world market: cod, salmon, tuna, and sea bass. While the supply of North American and European markets for two of these species - Atlantic salmon and European sea bass - mainly comes from fish farming, Atlantic cod and tunas are mainly caught from wild stocks. We address the question what will be the status of these wild stocks in the midterm future, in the year 2048, to be specific. Whereas the effects of climate change and ecological driving forces on fish stocks have already gained much attention, our prime interest is in studying the effects of changing economic drivers, as well as the impact of variable management effectiveness. Using a process-based ecological-economic multispecies optimization model, we assess the future stock status under different scenarios of change. We simulate (i) technological progress in fishing, (ii) increasing demand for fish, and (iii) increasing supply of farmed fish, as well as the interplay of these driving forces under different sce- narios of (limited) fishery management effectiveness. We find that economic change has a substantial effect on fish populations. Increasing aquaculture production can dampen the fishing pressure on wild stocks, but this effect is likely to be overwhelmed by increasing demand and technological progress, both increasing fishing pressure. The only solution to avoid collapse of the majority of stocks is institutional change to improve management effectiveness significantly above the current state. We conclude that full recognition of economic drivers of change will be needed to successfully develop an integrated ecosystem management and to sustain the wild fish stocks until 2048 and beyond.

Improving income and livelihood of poor farming household in Bangladesh through adoption of improved aquaculture technologies and varieties

Fish are an important part of Bangladeshi culture and diet. Bangladesh ranks among the top five freshwater fish producers in the world. Fish are abundant in the thousands of rivers, ponds, lakes and seasonal floodplains across the country. They are a major source of protein for people living near these water bodies. In Bangladesh, many households depend on fish farming for their livelihood. By growing fish in homestead ponds, households have a consistent supply of nutritious fish and can sell the surplus for an income. The USAID-funded Cereal Systems Initiative for South Asia in Bangladesh (CSISA-BD) aimed to increase the income of farming households through increased productivity of aquaculture systems. Key activities of the project included developing and disseminating appropriate improved agricultural technology and quality fish seeds to improve livelihoods, food security and nutrition.

Mercury contamination in fanned fish setup on former garimpo mining areas in the Northern Mato Grosso State, Amazonian region, Brazil

The garimpo gold mining activity has released about 2.500 tons of mercury in the Brazilian Amazonian environment in the 1980-1995 period. The northern region of Mato Grosso State, an important gold mining and trading area during the Arnazonian gold rush is now at a turning point regarding its economic future. Nowadays, the activities related to gold mining have only a low relevance on its economy. Thus, the local communities are looking for economic alternatives for the development of the region. Cooperative fish farming is one of such alternatives. However, some projects are directly implemented on areas degraded by the former garimpo activity and the mercury left behind still poses risks, especially by its potential accumulation in fish. The objective of the present study was to evaluate the levels of mercury contamination in two fish farming areas, Paranaita and Alta Floresta, with and without records of past gold-washing activity, respectively. Data such as mercury concentration in fish of different trophic level, size, and weight as well as the water physical and chemical parameters were measured and considered. These preliminary data have shown no significant difference between these two fish fanning areas, relatively to mercury levels in fish. (c) 2004 Elsevier B.V. All rights reserved.

Acute lethal and sublethal effects of neem leaf extract on the neotropical freshwater fish Prochilodus lineatus

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 It LC(50) of neem leaf extract for juveniles P lineatus was estimated as 4.8 g L(-1); the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L(-1) or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L(-1) and 5.0 g L(-1) neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L(-1). Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species. (c) 2006 Elsevier B.V. All rights reserved.

Optimal allocation of water in village irrigation systems of Sri Lanka

This PhD study examines whether water allocation becomes more productive when it is re-allocated from 'low' to 'high' efficient alternative uses in village irrigation systems (VISs) in Sri Lanka. Reservoir-based agriculture is a collective farming economic activity, which inter-sectoral allocation of water is assumed to be inefficient due to market imperfections and weak user rights. Furthermore, the available literature shows that a „head-tail syndrome. is the most common issue for intra-sectoral water management in „irrigation. agriculture. This research analyses the issue of water allocation by using primary data collected from two surveys of 460 rice farmers and 325 fish farming groups in two administrative districts in Sri Lanka. Technical efficiency estimates are undertaken for both rice farming and culture-based fisheries (CBF) production. The equi-marginal principle is applied for inter and intra-sectoral allocation of water. Welfare benefits of water re-allocation are measured through consumer surplus estimation. Based on these analyses, the overall findings of the thesis can be summarised as follows. The estimated mean technical efficiency (MTE) for rice farming is 73%. For CBF production, the estimated MTE is 33%. The technical efficiency distribution is skewed to the left for rice farming, while it skewed to the right for CBF production. The results show that technical efficiency of rice farming can be improved by formalising transferability of land ownership and, therefore, water user rights by enhancing the institutional capacity of Farmer Organisations (FOs). Other effective tools for improving technical efficiency of CBF production are strengthening group stability of CBF farmers, improving the accessibility of official consultation, and attracting independent investments. Inter-sectoral optimal allocation shows that the estimated inefficient volume of water in rice farming, which can be re-allocated for CBF production, is 32%. With the application of successive policy instruments (e.g., a community transferable quota system and promoting CBF activities), there is potential for a threefold increase in marginal value product (MVP) of total reservoir water in VISs. The existing intra-sectoral inefficient volume of water use in tail-end fields and head-end fields can potentially be removed by reducing water use by 10% and 23% respectively and re-allocating this to middle fields. This re-allocation may enable a twofold increase in MVP of water used in rice farming without reducing the existing rice output, but will require developing irrigation practices to facilitate this re-allocation. Finally, the total productivity of reservoir water can be increased by responsible village level institutions and primary level stakeholders (i.e., co-management) sharing responsibility of water management, while allowing market forces to guide the efficient re-allocation decisions. This PhD has demonstrated that instead of farmers allocating water between uses haphazardly, they can now base their decisions on efficient water use with a view to increasing water productivity. Such an approach, no doubt will enhance farmer incomes and community welfare.

Recommendation domains for pond aquaculture: country case study: development and status of freshwater aquaculture in Henan Province, China

This monograph is the case study for China, with a particular focus on Henan Province, the project location. Written in three parts, it first describes the historical background, production levels and trends, economic and institutional environment, policy issues, and market situation in China in general. The main part of the study presents findings from two different surveys conducted in Henan Province. County-level information is used to analyze the current situation of aquaculture, providing a more disaggregated picture than what is generally available from national statistics. Data collected in a survey of fish farmers in two locations in Henan are then analyzed with regard to the prevailing aquaculture technology and production practices, economic performance of pond fish farming, and the key reasons for aquaculture adoption. In the final chapter, constraints and opportunities for the aquaculture sector in China in general are discussed. (pdf contains 68 pages.)

Aquaculture Asia, Vol.14, No.1, pp.1-51, January-March 2009

Peter Edwards writes on rural aquaculture: Myanmar revisited. Harvesting, traditional preservation and marketing of fishes of Chalan Beel, Bangladesh, by Galib, S.M. and Samad, M.A. Role of community in production and supply of larger, quality fingerlings, by Radheyshyam, De, H.K. and Saha, G.S. Can rice-fish farming provide food security in Bangladesh? by Ahmed, N. and Luong-Van, J. Nutritional and food security for rural poor through multi-commodity production from a lake of eastern Uttar Pradesh, by Singh, S.K. Emerging boost in Sri Lankan reservoir fish production: a case of adoption of past research findings, by Amarasinghe, U.S., Weerakoon, D.E.M., Athukorala, D.A. Farming the freshwater prawn Macrobrachium malcolmsonii, by Radheyshyam Breeding and seed production of butter catfish, Ompok pabda (Siluridae) at Kalyani Centre of CIFA, India, by Chakrabarti, P.P., Chakrabarty, N.M. and Mondal, S.C. Asia-Pacific Marine Finfish Aquaculture Magazine Use of fish in animal feeds: a fresh perspective National strategies for aquatic animal health management, by Mohan, C.V. NACA Newsletter.

Genetic improvement and effective dissemination: keys to prosperous and sustainable aquaculture industries

There is an increasing demand for fish in the world due to a growing population, better economic situation in some sectors, and greater awareness of health issues in relation to food. Since capture fisheries have stagnated, fish farming has become a very fast growing food production system. In this presentation, the author gives an overview of the technologies that are available for genetic improvement of fish, and briefly discuss their merit in the context of a sustainable development. He also discusses the essential prerequisites for effective dissemination of improved stock to farmers. It is concluded that genetic improvement programs based on selective breeding can substantially contribute to sustainable fish production systems. Furthermore, if such genetic improvement programs are followed up with effective dissemination strategies, they can result in a positive impact on farmers' incomes.

Adapting integrated agriculture aquaculture for HIV and AIDS-affected households: the case of Malawi

The WorldFish Center in conjunction with World Vision Malawi carried out a project to improve income and nutrition status of households affected by HIV and AIDS with funding from the World Bank. The project was implemented in Southern Malawi particularly in the West of Zomba District from July 2005 to June 2006. Through participatory approaches, the project identified constraints that limit HIV and AIDS affected households’ realisation of the benefits from fish farming and adapted technologies and practices for the affected beneficiaries to boost fish production and utilization. Specifically, the project sought (1) to identify the constraints that limit HIV and AIDS affected households to realise the benefits from fish farming and based on the constraints, (2) to adapt technologies and practices for use by the affected beneficiaries to boost fish production and utilization. (PDF cotains 17 pages)

Keynote address on production, utilization and marketing in fisheries status and opportunities

Fish production from Nigeria comes mainly from 3 sources, namely - artisans engaged in either part-time or full-time fishing, commercial trawlers fishing in inshore and offshore waters, and fish farming in enclosures (ponds, tanks and raceways). An account is given of the current situation in Nigeria, considering over exploitation of fish, the fish's environment, fish utilization, and fish marketing

Investment in the training of technologists for commercial aquaculture

The protein shortage in Nigeria is noted and the role of aquaculture (=fish farming) as a complement in increasing the dwindling food supply is registered. In addition, the manpower shortage especially in the technology cadre is noted and attributed to the lack of co-ordination and standard curricula especially in aquaculture. An inventory of tasks performed in the aquaculture industry was taken and these were classified and validated, then their final priority level was used to assess which ones were critical, important or desirable and which ones would result in disaster or not with inadequate mastery. Based on the above, recommendations are made that all critical and important tasks be included in the teaching curriculum for aquaculture in both theory and practicals: while it is advocated that all tasks listed be undertaken in fish farm operations. This will raise the competence of technologists to run the commercial aquaculture projects

Conservation needs of fisheries resources and reorientation for sustainable captive and culture practices

A discussion is presented on the importance of conservation of fishery resources, considering in particular the situation in Nigeria and providing also an outline of various legislations made by government. Suggestions are given regarding the following: education on the importance of conservation; fish farming or aquaculture; restocking or rejuvenation of depleted water bodies; stock assessment; monitoring and surveillance; provision of fishing inputs; and, extension research linkage

Hatchery construction and its feasibility in the Nigerian economy

Aquaculture drive in the Niger Delta has necessitated the springing up of various forms of hatcheries in Nigeria in the area. The hatchery level is high as most fish farmers now want to produce their own fingerlings for the stocking of their production ponds for culture to market (table) size. The paper shows that there is a lot of market in the Niger-Delta for fresh fish. Majority of the numerous fish farmers are not well empowered to breed and produce fish seeds especially species most loved and eaten. The rising cost of materials in the Nigerian economy has become a bottleneck in the construction of more fish hatcheries for fingerling production. However, the assistance of multinationals has become very necessary to enhance its feasibility to encourage better involvement in the fish hatchery works. One remarkable area where assistance is being felt by the communities in the Niger-Delta is in fish farming and more so in the supply of fish fingerling to top fish farmers by The Shell Petroleum Development Company of Nigeria Limited (SPDC), a multinational oil company in the area. Few fish farmers have benefited from this. If more hatcheries are available to service and provide the needed fingerlings to stock the available water bodies such as, home backyard ponds, the 0.74 million hectares of brackish water, 1.01 million hectares of perennial swamps, and other marginal land available for aquaculture and properly managed, it will yield between 2.5 and 10 metric tones of fish depending on the species stocked and bred

The status of Arctic charr, Salvelinus alpinus (L.), in southern Scotland: a cause for concern

The objective of this article is to review the populations of Arctic charr in the south of Scotland which have become locally extinct, and the reasons for their demise. In the British Isles, the Arctic charr in individual lakes have been isolated from each other for thousands of years and have developed a variety of phenotypic characteristics which are probably genetically based. About 200 populations of Arctic charr have been recorded from different parts of the British Isles: approximately 12 in England, 50 in Ireland, 175 in Scotland and four in Wales. The threats to charr from acidification, afforestation, engineering schemes, angling and fish farming are assessed, and the establishment of new populations is proposed as a method of replacing extinct stocks or providing an additional safeguard for valuable stocks in threatened waters.