This thesis explores problems of optimal investment arising in fisheries and other renewable resource industries. In such industries, two simultaneous investment problems must be addressed: investment in the resource stock (the biomass) and investment in the capital stock (harvesting capacity). Each of these investment problems faces a key complication; investment in the resource is constrained by the natural population dynamics, while in many cases investment in the physical capital stock suffers from irreversibility, since capital used in natural resource industries is often non-malleable. In addition, all investment decisions must be made within an uncertain environment; full information is never available. Building upon the work of Clark, Clarke and Munro (Econometrica, 1979), we develop a two-state two-control model which incorporates investment delays and stochastic resource fluctuations within a seasonal (discrete-time) framework. A dynamic programming approach is used to analyse the model heuristically and to obtain numerical results, beginning with a study of the ideal deterministic case and proceeding to a full stochastic analysis. The key assumption of irreversible investment is maintained throughout the thesis. We have examined the qualitative and quantitative effects on optimal investment strategies of several economic and ecological factors: (i) delays in investment, (ii) population dynamics parameters, (iii) selling price, (iv) capital cost and operating cost, (v) depreciation rate, (vi) discount rate, and (vii) the level of uncertainty in the resource stock. We have found that the key cost parameter for the investment problem is the ratio of unit capital costs to unit operating costs. Depreciation can play a rather counter-intuitive role; in some circumstances optimal investment levels can increase with the depreciation rate, contrary to the usual treatment of depreciation as an additional cost of capital. The introduction of uncertainty in the form of stochastic resource fluctuations can substantially change the optimal investment policy, but this tends to have little effect on the value of the fishery. We analyse the factors which determine the role of randomness in optimal fisheries investment, and discuss in some detail the implications for management. Solution of the stochastic optimization problem studied here requires the use of rather complicated numerical methods, which are described in detail in the thesis. These methods are quite general, and should prove useful in analysing other related stochastic models. / Science, Faculty of / Mathematics, Department of / Graduate

Based in Walvis Bay, an industrial fishing town in Namibia on the west coast of southern Africa, this thesis argues that via the logic of neoliberalism, relations between scientific knowledge production, historical labour practices, and political decision-making emerge as a way of managing people and nature in uneven ways. Scientific modelling practices in the form of stock assessments, maintain traction as the technological solution for managing natural resource extraction in Namibia. As such, the dissertation explores the efficacy of computer models in the industrial fishing sector and considers how breakdowns between the scientific, social, and political knowledge worlds can be usefully brought into the conceptual model of the fishery for management. With a shift towards a more inclusive management framework that considers the policy issues as well as translating broad goals into measurable objectives, comes a shift in the logic of what fisheries management is meant to mediate and achieve. The logic is no longer as straightforward as producing an estimate of the amount of fishable biomass, but now must account for market conditions, changing technologies for fishing, and a changing climate and ecology. The human dimension is framed around the concept of wellbeing which in fisheries management emerges as an umbrella term for the social world that is reduced through the logic of neoliberalism to the measurable, enumerable, and indexable social and political implications of the use of Namibia’s natural resources. As one of few ethnographies of Namibia and the only one thus far to address the fisheries sector as a site of study, this dissertation investigates the increased dependence on scientific models in the Namibian hake fishery despite declining fish stocks and increased urban poverty and inequalities. The research contributes to the limited studies done on the political economy of Namibia and the rise of fish as national resource in the postcolony. It investigates the relations at risk in everyday life in Walvis Bay and re-imagines the framing of humans and nature for transformative practices of environmental and economic justice.

The thesis tested the notion of collective ownership in the small-scale fisheries sector, as advocated by the Department of Agriculture, Forestry and Fisheries, the South African government department responsible for fisheries administration. More specifically, it examined the conditions under which collective ownership would yield economic benefits to small-scale fishers. This was done according to three constructs, i.e. collective entrepreneurship, agency theory and value chain development. In testing the study’s presuppositions, a sequential qualitative-quantitative mixed methods research methodology was used. Data were gathered through focus group discussions, individual interviews and surveys with fishers from South Africa’s Western Cape and Northern Cape provinces. Qualitative data were analysed through the constant comparative approach preliminary outcomes thereof were used to devise the quantitative instruments, which were analysed with the SPSS statistical package. The outcomes of the quantitative data analysis were then discussed with key participants to validate the findings and to ensure overall congruency. In the current value chain dispensation, small-scale fishers realise approximately 38% of overall revenue accrual, whereas the remaining 62% is realised by fish-processing establishments and exporters. The value chain requires reconfiguration to progressively enable small-scale fishers to own and control all upstream and downstream catch, processing and marketing processes. In addition, greater value can be realised when all regulatory, catch, processing and marketing processes are efficiently aligned with local and export market requirements. The findings note that small-scale fishers require developmental support to exploit opportunities. The study suggests that the required support should be facilitated through a dedicated multi- and interdisciplinary fisheries institute located at a higher education institution. This institute needs to focus on training, advisory services and research, as well as on defined support for the fisheries co-operatives. Moreover, the impact of the envisaged institute provides for the establishment of localised fishing community information centres, located near coastal fishing communities, harbours and slipways. Such centres ought to improve communications, trust-building relations and shared expertise among all actors, namely small-scale fishers, their co-operatives, the various government departments, industrial associations, non-governmental organisations, agencies and all others implicated, to maximise benefit and effectively secure government’s infrastructural investment programme within the small-scale fisheries sector.

No description available.

In the aquaculture of fish and shrimps, diets generally contain high levels of fish meal. Fish meal is a nutrient rich feed that contains essential amino acids and fatty acids, which are required to maintain optimum growth and health of an animal. It is traditionally used in aquaculture to promote feed efficiency, nutrient uptake and feed intake due to its high palatability and digestibility. Overexploitation of fisheries resources and the high growth rate of aquaculture industry, however, continues to put pressure on the supply of fish meal, thus increasing the demand and price of this sought-after product. The use of alternative ingredients to fish meal, therefore, remains a high priority for aquaculture nutrition. Hence, the aim of this was to investigate the physiological and developmental effects on juvenile spotted grunter, Pomadasys commersonnii, after supplementing fish meal with different feed additives for 12 weeks. One of the additives was then selected for further feeding at graded levels (increasing levels) for 8 weeks to ascertain whether fish meal could be replaced by higher amounts of the feed additive without negative consequences to the cultured spotted grunter.

The Utah chub is one of the most important non-game fish in Utah. It has a wide range, and occurs in every drainage in Utah. The Utah chub is not important economically as food fish nor is it of much value commercially. The sportsmen think of this species as trash and do not consider catching or consuming the. However, the Utah chub may be caught on hook and like more readily than many game species. The Utah chub in Scofield Reservoir have been caught by trolling, bait fishing and fly casting and furnish considerable sport when caught with a light tackle. Their real importance becomes evident when a large population of Utah chub exist in waters where game fish species are desired. With their high reproductive potential, the Utah chub may become the dominant species and cause trout populations to decrease. This competition for food and space has been evident in many areas. Hazzard (1935) stated that Utah chub and trout compete with trout for food in Fish Lake, Utah, and Sigler (1948) also found that Utah chub compete with trout for food.

With the goal of obtaining the maximum utilization of areas now open to public hunting in mind, a study was conducted at the Bear River Migratory Bird Refuge during the 1960 and 1961 waterfowl hunting seasons. The study had the following main objectives: 1) determine the level of utilization of the refuge by water fowl hunters including determining the factors which affect the utilization of various areas of the refuge, determining the factors and their influence on the kill composition in the various areas and the entire refuge, and obtaining quantitative and qualitative information on hunter population and the use it may have in interpreting behavior patterns of hunters; and 2) determine methods by which utilization of the refuge can be increased to accommodate the greatest number of hunters and still provide good hunting.

This project investigated several aspects of the autecology of the brackish water clam Rangia cuneata in the James River, Virginia. The study, conducted from August, 1970, through March, 1972, was primarily concerned with substrate and salinity effects on growth and condition index of R. cuneata. The studies were conducted in sand and mud substrates in four different salinity regimes. Monthly samples of 15 clams were collected at each of the eight stations for condition index determinations. Condition index was shown to vary seasonally, with a low point in early spring and a maximum in early fall. Values were higher in sand bottoms than in mud and decreased in both substrates in fresher water. Clams from sand bottoms showed a pronounced fall peak which was not evident at most mud stations. A field experiment to evaluate the relative importance of water associated and sediment-associated factors in determining condition index showed that some factor associated with the water pumped by the clams was most important. The hypothesis is presented that this factor may be related to the large difference in suspended solids taken in by clams in sand and mud bottoms. Growth studies were based on marked individuals planted at all eight stations and recovered after one year. Growth was measured in terms of shell length and live weight increases. In terms of both criteria, growth was greatest at the three downriver sand stations. The lowest salinity sand station showed considerably less growth, but exceeded the growth at all mud stations. Clams at the latter showed similar small increases in both length and weight. The above patterns of condition index and growth are discussed in relation to salinity structure and suspended solids in the environment and to osmotic stress and spawning activity of the clams. An explanation is offered for the large size and relatively high condition index of clams near their limit of penetration into fresh water. The potential commercial value and annual harvest of R. cuneata in the lower James River is estimated. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

The pallid sturgeon Scaphirhynchus albus is an endangered sturgeon distributed throughout the Mississippi River drainage. Habitat selection and movement have been identified as critical conservation information. Seventy-one pallid sturgeon were tagged with acoustic transmitters in the lower Mississippi River (LMR), and 53 sturgeon were tagged in the Atchafalaya River System (ARS). Twenty-two pallid sturgeon in the LMR and 30 in the ARS were monitored using stationary acoustic receivers to assess short-term movement. Pallid sturgeon in the LMR showed positive selection for island tip, outside-bend natural bank, wing dike, sandbar, outside-bend revetted bank, and secondary channel habitats. Pallid sturgeon in the ARS exhibited positive selection for both inside and outside-bend revetted banks, inside-bend natural banks, and water control structures. Fish selected against the main channel in both systems. Short-term movement in the LMR and ARS was minimal and not related to any of the tested environmental factors.

No description available.