A model is proposed to provide inventory and maintenance guidance for a system of operating parts. This model is capable of handling a system with multiple operating components, unknown part lifetime failure distribution, and separately maintained parts. In this model, part reliability characteristics are used along with system costs to predict the required stocking levels and part replacement times. Two maintenance strategies are presented that have the unique characteristic of allowing flexible scheduling of replacements. A case study is completed comparing developed stocking policies to an existing policy. An estimation selection method is introduced and fit into the model for computing Weibull distribution parameters when part reliability is not well known. An algorithm is displayed that describes the implementation of the system model and data from practical case scenarios are conducted using this algorithm.

There has been a continuous decline in both the production and general performance of the SRO in NSW estuaries over the past three decades. The relationship of this decline to both environmental and oyster-density related factors are assessed in this thesis. This question has been examined at different scales: a large scale that compares two different estuaries (Clyde and Shoalhaven Rivers, southern NSW); a regional scale that encompasses variations within an estuary and, at a lease scale that examines processes pertaining to individual or small groups of oysters. Levels of inorganic nutrients were in general very low potentially limiting primary production. The limiting nutrient was nitrogen or phosphorus depending on whether long term conditions were dry or wet, respectively. Only during rain events, through the input of terrestrial material, were conditions favourable for fast rates of primary production. Carbon and nitrogen isotope analysis has demonstrated that both external material and local resuspension of the benthos constitute a major proportion of the SRO diet. The uptake of the various food sources also varied considerably depending on local environmental conditions. Increases in SRO growth were strongly correlated to increases in temperature with a low temperature cut-off at ~13°C. Growth also appeared to reduce considerably when salinities lower than ~15ppt persisted for the order of a month. These factors may alter growth through changes in filtration rates. These processes were modelled in a coupled hydrodynamic-NPO (Nitrogen-Phytoplankton-Oyster) model of the Clyde River. This demonstrated that primary production was more affected by estuarine dynamics and nutrient concentrations than oyster uptake. At the current levels of oyster densities, primary production by itself could not account for the observed oyster growth, however growth became realistic with observed levels of POC added to the model. A set of environmental indices were used to complement the model and to assess the sustainability of the culture system. The combined indices indicated that while the ecological carrying capacity of the Clyde was exceeded the production capacity at an estuarine scale was not. On the lease scale, density experiments showed that while growth was not reduced as a result of current stocking densities, the condition index was significantly affected.

A single-beam acoustic seabed classification system was used to map coral reef environments in the upper Florida Keys, USA, and the Bahamas. The system consisted of two components, both produced by the Quester Tangent Corporation. A QTCView Series V, operating with a 50 kHz sounder, was used for data acquisition, and IMPACT software was used for data processing and classification. First, methodological aspects of system performance were evaluated. Second, the system was applied to the assessment of grouper and snapper habitat. Two methodological properties were explored: transferability (i.e. mapping the same classes at multiple sites) and reproducibility (i.e. surveying one site multiple times). The transferability results showed that a two-class scheme of hard bottom and sediment could be mapped at four sites with overall accuracy ranging from 73% to 86%. The locations of most misclassified echoes had one of two characteristics: a thin sediment veneer overlying hard bottom or within-footprint relief on the order of 0.5 m or greater. Reproducibility experiments showed that consistency of acoustic classes between repeat transects over the same area on different days varied, for the most part, between 50% and 65%. Consistency increased to between 78% and 92% when clustering was limited to two acoustic classes, to between approximately 70% and 100% when only echoes acquired within two degrees of nadir in the pitch direction were used, and to between 81% and 87% when a limited set of features was used for classification. The assessment of grouper and snapper habitat addressed the question whether areas of high fish abundance were associated with characteristic acoustic or geomorphological signatures. The results showed, first, that the hard bottom / sediment classification scheme was a useful first step for stratifying survey areas to increase efficiency of grouper census efforts. Second, an index of acoustic variability complemented the hard bottom / sediment classification by further targeting areas of potential grouper habitat. Finally, five grouper and snapper spawning aggregation sites were all found to have similar associations with drowned shelf edge reefs in the upper Florida Keys.

De nos jours, la production agricole est soumise à certaines restrictions avec l'objectif de contrôler limpact environnemental et les volumes de production. Ces restrictions ont entrainé des modifications du niveau d'intensification de la production. En ce qui concerne lélevage des ruminants, le niveau d'intensification est défini par le chargement (animaux/ha) et la fertilisation minérale (kg/ha). La réforme de la Politique Agricole Commune (PAC) en 1992 a instauré des « méthodes de production agricole compatibles avec les exigences de la protection de l'environnement ainsi que l'entretien de l'espace naturel » (Règlement (CEE) N° 2078/92 du Conseil du 30 juin 1992, J.O.C.E. N°L 215 du 30/7/92 ; MRW, 1997). La réduction du niveau d'intensification de la production se trouvait parmi ces mesures. En élevage viandeux, elle était encouragée par l'octroi de primes aux éleveurs ne dépassant pas un seuil de chargement de 2 UGB/ha. Ces primes permettaient de compenser la perte de production due à la réduction du niveau dintensification. De plus, des primes à l'extensification pouvaient être obtenues pour les chargements inférieurs à 1,4 UGB/ha. Ces mesures, conjointement au système des quotas, ont permis de maîtriser aussi le volume de la production à grande échelle. Actuellement, suite au principe du découplage décidé lors de la réforme à mi parcours de lAgenda 2000 en juin 2003 et qui correspond aux dernières réformes de la PAC, loctroi de primes nest plus lié au volume des productions, mais bien à la surface. Chaque exploitant doit disposer de « droits » quil doit activer en justifiant les superficies correspondantes. Ces droits sont calculés sur base des superficies et des animaux qui ont donné lieu à un paiement daides directes au cours des années de références 2000, 2001 et 2002. Une fois les droits justifiés et un ensemble de conditions appelées « conditionnalité », liées à lenvironnement (Directive Nitrate), à la sécurité alimentaire et au bien-être des animaux, respectés, lexploitant pourra obtenir le «paiement unique». Les Etats Membres peuvent choisir de découpler certaines productions comme cest le cas pour les vaches allaitantes en Belgique. De plus, les règlements liés à la « Directive Nitrate » ont permis de mieux prendre en compte les effluents délevage et ont provoqué une diminution de la fertilisation azotée susceptible de diminuer la production, lazote étant le premier minéral limitant pour la croissance végétale. Cependant, dans les prairies pâturées, on constate souvent un bilan azoté positif. Lazote en excès est susceptible de sortir du système en étant lessivé sous forme de nitrate avec un risque de pollution environementale. La réduction de l'intensification de la production obtenue soit par une réduction de la fertilisation azotée soit par la réduction du chargement ou les deux facteurs conjugués, peut provoquer une diminution des déjections déposées sur les parcelles et une réduction du bilan azoté. On peut ainsi obtenir une réduction de la pollution des eaux (notamment par les nitrates) ainsi que les émissions des composants azotés volatils (ammoniac et oxyde nitreux). Les résultats dune série d'essais menés pendant six années consécutives sur des prairies pâturées par les principaux types de spéculation bovine, la vache allaitante, la vache laitière et le taurillon, sont présentés et discutés dans cette thèse. Le fil conducteur des essais a été un protocole semblable dans ces trois spéculations. Ce protocole visait à comparer d'une part, la réduction de 33% de la fertilisation azotée sans réduction du chargement et d'autre part, le rapport entre ces deux systèmes et un système sans apport d'azote minéral. Les paramètres étudiés ont été les performances zootechniques, phytotechniques, le bilan azoté et, pour les spéculations des vaches laitières et des taurillons, les reliquats azotés dans le sol. En plus, dans la spéculation "taurillon", les trois lots soumis au pâturage ont été comparés à un lot engraissé en stabulation.

Small livestock is an important resource for rural human populations in dry climates. How strongly will climate change affect the capacity of the rangeland? We used hierarchical modelling to scale quantitatively the growth of shrubs and annual plants, the main food of sheep and goats, to the landscape extent in the eastern Mediterranean region. Without grazing, productivity increased in a sigmoid way with mean annual precipitation. Grazing reduced productivity more strongly the drier the landscape. At a point just under the stocking capacity of the vegetation, productivity declined precipitously with more intense grazing due to a lack of seed production of annuals. We repeated simulations with precipitation patterns projected by two contrasting IPCC scenarios. Compared to results based on historic patterns, productivity and stocking capacity did not differ in most cases. Thus, grazing intensity remains the stronger impact on landscape productivity in this dry region even in the future. / Kleinvieh ist eine wichtige Lebensgrundlage für die Landbevölkerung in trockenen Regionen. Wie stark wird sich der Klimawandel auf die Tragfähigkeit der Weideflächen auswirken? Wir benutzten hierarchische Modellierung, um das Wachstum von Sträuchern und einjährigen Kräutern, das wichtigste Futter für Ziegen und Schafe, quantitativ auf die Fläche von Landschaften in der östlichen Mittelmeerregion zu dimensionieren. Die Produktivität ohne Beweidung stieg sigmoidal mit dem mittleren Jahresniederschlag. Je trockener die Landschaft, desto stärker verminderte Beweidung die Produktion. An einem Punkt knapp unter der Tragfähigkeit der Vegetation, sank die Produktion stark mit zunehmender Beweidung, weil die Samenproduktion der Kräuter zu gering war. Wir wiederholten die Simulationen mit Niederschlagsverteilungsmustern gemäß zweier gegensätzlicher IPCC-Szenarien. Zukünftige Produktivität und Tragfähigkeit unterschieden sich in den meisten Fällen nicht von Ergebnissen auf Grund von historischer Niederschlagsverteilung. Allerdings war die zukünftige Produktivität in trockenen Habitaten der semiariden und trocken-mediterranen Regionen niedriger. Somit hat auch in Zukunft die Besatzdichte die größere Auswirkung auf die Produktivität dieser trockenen Landschaft als das Klima. "This abstract is provided by the authors, and is for convenience of the users only. The author certifies that the translation faithfully represents the official version in the language of the journal, which is the published Abstract of record and is the only Abstract to be used for reference and citation."

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The impact of undesirable plant communities (Cymbopogon afronardus and woody species dominated by Acacia species) on livestock carrying capacity and performance was investigated on 15 farms in an Acacia/Cymbopogon dominated pastoral system of south-western Uganda. Species prevalence based on basal cover for grasses, frequency for forbs and effective canopy cover for trees/shrubs were determined on farms. The PHYGROW model was used to predict forage productivity for computation of carrying capacity. The NIRS/NUTBAL nutritional management system was used to determine cattle dietary CP and DOM through fecal scans and to estimate animal performance. Cymbopogon afronardus had a prevalence of 10.29% among the grasses while Acacia gerrardii (34.37%) and Acacia hockii (33.66%) were the most prevalent woody species. Forage productivity differed significantly among the farms with a mean long-term annual forage yield of 4560(SE+41) kg/ha. Farms infested with Cymbopogon and woody species produced the least amount of forage and therefore had the lowest carrying capacities (0.38 -0.39 AU/ha) while improved farms had comparatively higher forage yields with higher carrying capacities (0.49 - 0.52 AU/ha). A mean carrying capacity for the system was estimated at 0.44 AU/ha using a 25% harvest efficiency for ANPP. All the farms were overstocked, on average by 3.2 times. Livestock BCS, diet CP and DOM were significantly different (P<0.0001) among the different farm types. BCS were highest on improved farms and lowest on Cymbopogon infested farms while dietary CP and DOM values were lowest on improved farms and highest on farms with a high woody component. Farms with a relatively high woody component exhibited intermediate BCS despite the high dietary CP values. Cattle on Cymbopogon infested farms had consistently lower body weights over the months although there were no significant differences in daily live weight gains among farms. Recommendations included need for research into appropriate control measures for both Cymbopogon afronardus and woody species, farmer sensitization about overstocking, research to improve forage quality on improved farms and need for feed supplementation for improved breeds on improved farms. Integration of NIRS/NUTBAL and PHYGROW models into the research and management systems was desirable. The observed increase in Sporobolus spp. required investigation.

Stocking trout to create successful sport fisheries is an irresistible lure to fisheries managers and sport anglers alike, but the implicit assumptions behind this simple process have seldom been questioned or assessed. Using common fisheries monitoring techniques, combined with social surveys, at nine Alberta lakes, I quantified three main assumptions behind put-and-take stocking. Surprisingly, 1) stocking high densities of Rainbow Trout created very low-density populations; 2) these populations supported mediocre fisheries; 3) these mediocre fisheries, if above a threshold catch rate, attracted very large numbers of satisfied anglers. Based on these findings, the stocking density and the direct cost of stocking were reduced by 80% at three experimental lakes. No major decreases in fishing quality, angler participation, or angler satisfaction were observed. I suggest refinements in the stocking process focus on determining how to provide adequate numbers of trout to create a basic level of satisfaction with the fishing experience.

For several millennia man has in some way farmed his waters by holding fish captive in ponds. Not until the second half of the nineteenth century, however, as a result of a general concern in the industrialised nations that fishery stocks were declining, were serious attempts made to breed fish artificially. The most concerted of these attempts in Britain effectively began in 1873 when Sir James Maitland (1848-1897), a Scottish landowner, commenced experiments which evolved into the construction of the world's largest salmonoid piscicultural establishment. This operation, the Howietoun Fishery, sold its produce nationally on the open market, a new departure in pisciculture. It also advanced the piscicultural process scientifically in selectively breeding fish superior to nature's own. Maitland's work was not, in itself, particularly successful commercially. This was not, however, the result of commercial failure on his behalf but rather a reflection of his desire to develop pisciculture for the public good in an attempt to restock impoverished fisheries and to disseminate knowledge in the hope that others would be encouraged to imitate his example on a more commercial basis. Maitland's piscicultural work was highly important to the development of what has today become a significant global industry, though his contribution has not hitherto been recognised. The thesis intends to set out Maitland's piscicultural advances and their significance. It offers a detailed analysis of Maitland's entrepreneurship and casts its net wider to draw in some discussion of his work away from Howietoun, particularly on his membership of the Fishery Board for Scotland where it examines the debate over state support for nineteenth century British science. The thesis concludes with an analysis of the development of Howietoun in the seventy years after its founder's death. In addition to Maitland's own writings, the thesis uses evidence from Howietoun's general records, Maitland's family papers, Fishery Board for Scotland material, and a very wide variety of published sources.

Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2008.