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No description available.

In recent years, freshwater fish farmers have come under increasing pressure from the Water Authorities to control the quality of their farm effluents. This project aimed to investigate methods of treating aquacultural effluent in an efficient and cost-effective manner, and to incorporate the knowledge gained into an Expert System which could then be used in an advice service to farmers. From the results of this research it was established that sedimentation and the use of low pollution diets are the only cost effective methods of controlling the quality of fish farm effluents. Settlement has been extensively investigated and it was found that the removal of suspended solids in a settlement pond is only likely to be effective if the inlet solids concentration is in excess of 8 mg/litre. The probability of good settlement can be enhanced by keeping the ratio of length/retention time (a form of mean fluid velocity) below 4.0 metres/minute. The removal of BOD requires inlet solids concentrations in excess of 20 mg/litre to be effective, and this is seldom attained on commercial fish farms. Settlement, generally, does not remove appreciable quantities of ammonia from effluents, but algae can absorb ammonia by nutrient uptake under certain conditions. The use of low pollution, high performance diets gives pollutant yields which are low when compared with published figures obtained by many previous workers. Two Expert Systems were constructed, both of which diagnose possible causes of poor effluent quality on fish farms and suggest solutions. The first system uses knowledge gained from a literature review and the second employs the knowledge obtained from this project's experimental work. Consent details for over 100 fish farms were obtained from the public registers kept by the Water Authorities. Large variations in policy from one Authority to the next were found. These data have been compiled in a computer file for ease of comparison.

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.

This thesis explores the physical and the socio-economic conditions for aquaculture in Tabasco, Mexico, seeking to find how aquaculture can best be supported to reduce poverty. On-farm physical, technical and social surveys were carried out in four municipalities, covering different physiographic regions. The surveys establish that the environmental conditions are frequently good for aquaculture. Despite efforts to bring farmers into more intensive commercial systems, aquaculture has developed mainly to improve subsistence, as one component of semi-subsistence farms. In order to evaluate these semi- subsistence systems, the thesis explores current debates on 'sustainability' and on 'subsistence'. As no single approach to sustainability per se seems appropriate to apply to these systems, new indicators and methods need to be developed which are appropriate to evaluate systems poor in cash generation but rich in social assets. Subsistence aquaculture is arguably more sustainable than commercial, monocultural aquaculture in environmental and social terms. It has become part of the economic diversity of the communities, increases food security, reduces the use of fossil fuels, promotes the careful management and recycling of wastes and the careful stewardship of natural resources, can help in the protection and enhancement of biological diversity and yields a feeling of self- empowerment. From the surveys, socio-economic and cultural realities are more important than physical conditions in determining the present state of aquaculture in Tabasco. The existence of some successful farmers' micro-businesses shows that once farmers receive continuous technical assistance, subsidies and access to markets, bringing them into commercial aquaculture is possible. Such help however, is rarely provided at present by the local extension institutions, which face internal problems resulting from inadequate budgets. This thesis argues that, in these circumstances, semi-subsistence aquaculture is a good option for the poor as many semi-subsistence systems are highly valued and have the potential to become more efficient and productive if locally based research is conducted with an understanding of farmers' cultures and motivations.

No description available.

This thesis is concerned with identifying some of the factors which affect the flesh quality of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). The flesh of any food animal is of utmost importance. Much work has been carried out on the flesh of land animals, but comparatively little is known about the factors which affect the quality of fish flesh. Salmonids have been farmed for a relatively short period of time, but great advances have been made in the techniques for their rearing. Now that the fish can be grown easily, more information is required on the factors which affect their fish quality in order to produce a consistent product. Fish fed a high oil diet have a significantly higher level of flesh lipid than fish of the same size fed a low oil diet (uncertainty p < 0.001). This has implications for the eating quality of the fish as many attributes of the eating quality of smoked salmon are significantly affected by the flesh lipid content. The flesh texture becomes softer and the flavours stronger, apart from salty flavour which decreases dramatically with increasing lipid (p < 0.001). The general effect of increasing lipid is to increase the perception of overall flavour and the overall liking of the product, as judged by the ten person trained taste panel. In contrast there are much fewer effects of the lipid content on cooked salmon and there are no effects on the overall flavour or overall liking (p > 0.05). The colour of the flesh is of great importance to the flesh quality of salmonids. Stress at slaughter is known to affect the muscle chemistry post-slaughter. This work shows that reducing stress at slaughter significantly increases the colour of the flesh, resulting in lower lightness (p < 0.05), an increased red hue (p < 0.05) and reduced opacity (p < 0.05) as measured using the CElab 1976 method. The change in colour is also shown by an increased Roche colour card score using the subjective colour card score (p < 0.05). Reduced stress at slaughter is also found to result in a longer time to the onset of rigor (p < 0.001) and a reduced susceptibility to gaping of the flesh (p < 0.01). Current commercial 'best practice' methods of slaughter were found to be highly stressful to the fish. The red colour of the flesh has been previously reported to reduce during storage, but this research found no changes in the level of the pigment astaxanthin during 12 days of storage of salmon fillets on ice. No effects of the level of astaxanthin or the antioxidant vitamins ascorbic acid and a-tocopherol at slaughter were found on the eating quality of the cooked flesh, either fresh or after 12 days storage on ice. However, many other attributes of the eating quality were significantly affected during the storage period, with increases in many flavours and textures associated with "off' fish. This translated into a significant reduction in the expression of overall liking by the trained taste panel (p < 0.001). The research for this thesis has shown areas where further research is required to investigate factors having effects on flesh quality. The most important of these new areas is the effect of stress level at slaughter on flesh quality. There is a strong possibility that stress at this point has wide ranging effects, the results of which may actually confound improvements introduced into in other areas of quality control unless they are eliminated from salmon farming practices.

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This research contributes to the discussion surrounding New Zealand’s entrepreneurial environment and Innovation Framework and addresses the research problem of whether the New Zealand government should seek to support entrepreneurship and innovation through the various knowledge-based or regulatory organisations it owns or funds, and if so, how it should go about accomplishing this. The approach taken was to use qualitative methods to examine how the government’s support for entrepreneurship and innovation was delivered to an emerging cluster of entrepreneurs from the point of view of those entrepreneurs. The entrepreneurs were involved in the innovative industry of land-based aquaculture and fieldwork was carried out in the Gisborne Region, on the east coast of the North Island of New Zealand. This study began by reviewing relevant literature from academic, industry and government sources to identify relevant sub-themes and create a framework for analysis. Fieldwork was undertaken using ethnographic methods to explore how the entrepreneurs experienced the New Zealand entrepreneurial environment and innovation framework in their interactions with knowledge-based and regulatory organisations. Data was gathered primarily by participant observation and semi-structured interviews and transcripts were coded and analysed using NVivo® software. An ethnographic narrative was produced and the interview transcripts analysed for relevance to the sub-themes from literature and to identify patterns that emerged from the data. This research reports that four of the entrepreneurs failed in their ventures due to a combination of factors both within their operations and within the entrepreneurial environment. These factors included technical difficulties maintaining livestock health and growth within an artificial marine environment, an inability to obtain assistance from knowledge-based organisations, problems in dealing with regulatory organisations, difficulty retaining trained staff, uncertainty about the market, and high energy costs. The Māori training organisation, Turanga Ararau, formed the Gisborne Aquaculture Society in an effort to establish a Gisborne aquaculture cluster however, this initiative proved unsuccessful primarily because the society failed to attract the 12 involvement of key stakeholders. This research contributes to the policy and practice of cluster facilitation by examining the extent to which best practice was followed in this attempt to establish a cluster and presents conclusions as to how the process of establishing the cluster could have been improved. This study also reports that the entrepreneurs were cut off from access to knowledge and research resources and received little advice or support from the knowledge based organisations that might have played a role in the development of their cluster. It examines how and why New Zealand’s Innovation Framework might be failing to recognise and support the vital role of entrepreneurs in economic development and suggests how this might be improved. The methodology chapters of this thesis contribute to literature regarding the use of ethnographic methods in entrepreneurship research and a further by-product of this thesis is an ethnographic account of the participant observation and semi structured interviews with the entrepreneurs. This research also provides an insight into the obstacles and challenges faced by entrepreneurs in New Zealand, in particular those involved in the emerging recirculating aquaculture industry.