The aim of this thesis is to define and study harvesting models of fish populations. These models are applied to particular fish species e.g., haddock and cod. The thesis is divided into five chapters: The first chapter is considered as an introductory one. In it, basics of fish biology and the recruitment process are defined. Two simple recruitment models known by the names Ricker and Beverton-Holt are used. In the second chapter the generalized Leslie model or Usher model is introduced. In section 2.2, some matrix theory is presented. For this matrix model, the net reproductive number is defined and studied in section 2.3. It turns out to be more useful than the spectral radius. In section 2.4, this study is extended to nonlinear matrix models. The nonlinearity, however, is defined only by the recruitment process. This allows to determine the equilibrium components. Finally section 2.5, the local stability of nonlinear matrix models is analyzed. Harvesting of such general matrix model is defined in chapter 3. We distinguish three different harvesting models (selective, net and semicontinuous harvesting models). In chapter 4, these harvesting models are then applied to concrete fish populations and analyzed with respect to its various parameters. In chapter 5, the stability is studied again along the lines of the paper of Levin, Goodyear [18]. The key results in this study are: 1) The maximum sustainable yields for selective harvesting and net harvesting are rather close. 2) Semicontinuous harvesting is more realistic harvesting models. 3) From a quantitative point of view, the choice of the recruitment function is important. 4) Harvesting process increases mortality and stability when we used Ricker recruitment model. 5) Stability of populations always holds if we use Beverton-Holt recruitment model.

Anthropogenic pressures have caused changes in both the mean and variance of environmental conditions, with associated effects on the demography of natural populations. The demographic effects of environmental change can manifest through direct (i.e., physiological) or indirect pathways (i.e., through shifts in species interactions). For many populations, environmental change will affect multiple life cycle stages simultaneously, thereby altering vital rate correlation structures with potentially important impacts on evolutionary fitness. The effects of environmental change will also often be habitat-specific, particularly when species interactions modify demographic sensitivity to climate. As a result, the effects of climate change are likely to vary across a species range, with important implications for range expansion and population viability. In chapter 2, I examine the effects of joint vital rate responses to environmental drivers on the evolution of life histories in variable environments. I show that vital rate covariation, generated when multiple vital rates respond to a shared environmental driver, can fundamentally alter evolutionary selection pressures. Negative vital rate covariation promotes the evolution of demographic lability (stronger demographic responsiveness), while positive covariation promotes buffering (weaker demographic responsiveness), altering the range of life histories over which the evolution of buffered and labile vital rates are a predicted evolutionary outcome. By identifying the life histories for which selection pressures are most sensitive to environmentally-driven vital rate covariation, this study provides a richer understanding of both life history evolution and the capacity of species to cope with ongoing changes to contemporary environments. In chapter 3, I use a long-term study of lesser snow geese to test the hypothesis that demographic and developmental responses to climate will be weakest in habitats where resource diversity is greatest. I find support for this hypothesis, and my results indicate that gosling demography is much more responsive to climate in recently colonized, freshwater habitats where landscape diversity and gosling diet diversity is low. These results underscore the potential importance of accounting for biotic interactions when predicting spatio-temporal responses to climate. In chapter 4, I quantify the consequences of observed climate change for lesser snow goose population dynamics across habitats. I find that climate change increases population growth in all habitats, but that such increases are disproportionately large in novel inland freshwater habitats. These results suggest that in a warmer and more variable climate, the breeding range and population growth of lesser snow geese is likely to increase, counteracting current management efforts to reduce overabundant populations.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18786号 / 理博第4044号 / 新制||理||1582(附属図書館) / 31737 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川合 光, 教授 畑 浩之, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Effective risk communication is based on appropriate risk characterization. A reevaluation of the 1987 US EPA radon risk categorization of Unicoi County Tennessee was conducted using in-home radon concentrations, determined in a long-term monitoring study. Radon concentrations were measured in 69 homes using Electret Passive Environmental Radon Monitors (E-PERM’s), following standard methods. Radon concentrations determined in this study (avg. 4.03 ± 3.04) were significantly higher than those measured in the USEPA study (avg. 1.96 ± 1.08). Using this study’s data, the risk categorization was recalculated with the US EPA Radon Index Matrix Model. The model re-categorized Unicoi County from a moderate to a high risk zone classification. These results suggest that the health risks associated with in-home radon concentrations are inaccurately categorized and communicated to the citizens of Unicoi County, Tennessee.

Species have complex and contextual relationships with their environment; both the relative contributions of life-history stages to population growth and the effect of environmental factors on each stage can be different among co-existing species. Timing and extent of reproduction, survival, and mortality determine population growth, species distributions, and assemblage patterns. I evaluate the role of habitat (intact, degraded) and microsite (shrub, leaf litter, bare sand) on population dynamics of Florida scrub herbs. Isolated overgrown shrubs and extensive bare sand areas in degraded scrub were expected to decrease seed predation, reduce competition of herbs with shrubs, and provide larger habitat for recruitment. I provide evidence that habitat and microsite variation influenced demography of five endemic and two common native species through effects on seed removal, emergence, and establishment. Habitat and species affected seed removal: endemic species with large seeds were removed in higher frequency in degraded habitat, likely by vertebrates, while species with small seeds were removed in higher frequency in intact habitat, by invertebrates. There was no evidence of differences in individual seed production between habitats for the two common species, C. fasciculata and B. angustifolia. Invertebrates were primarily responsible for seed removal of both species, although peak season of removal and microsite varied with species. Removal of seeds, emergence, and establishment increased with seed density. Matrix modeling indicated that population growth of C. fasciculata was greater in degraded habitat and greatest in litter microsites, and population growth of B. angustifolia was similar between habitats and greatest in bare sand. Contrasting responses among species to environmental factors in intact and degraded scrub indicated that natural disturbances are not ecologically equivalent to anthropogenic iv disturbances. Idiosyncratic species dynamics in common environments suggest that understanding relationships between life-history traits and environmental conditions will be required to facilitate restoration

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24168号 / 理博第4859号 / 新制||理||1695(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 笹倉 直樹, 准教授 髙山 史宏, 教授 橋本 幸士 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

No description available.

No description available.

<p><strong>Aim:</strong></p><p>The purpose was to perform a pre-study to marketing planning for a local squash club in Sweden that had difficulties with membership growth and development. This pre-study would provide the squash club with valuable information and a starting point when creating its first marketing plan.</p><p><strong>Method:</strong></p><p>The chosen research approach included theoretical and empirical studies. Empirical data was collected by triangulation, using both qualitative and quantitative methods. A semi-structured interview and two surveys using on-line questionnaires were conducted, analyzed and presented. The discussed theory including key definitions, models and concepts was related to the empirical data findings and reflected on.</p><p><strong>Results & Conclusions: </strong></p><p>A small non-profit squash club with scarce resources and slim organization has to implement a customer centered mindset and work smarter instead of harder.It is important for the club to carefully match market opportunities with its objectives and capabilities.Engaging in marketing planning and the development of a marketing plan will enable the club to find new creative ways to offer a unique squash experience that will result in a positive membership development.</p><p><strong>Recommendations:</strong></p><p>The squash club should strive to develop key strategic partnerships that can compliment its strengths and help reduce its weaknesses.An own club website would improve internal and external communication significantly and decrease the club management’s administrative workload.It would be advisable for the club to perform annual online customer satisfaction surveys to monitor and measure own performance and detect key changes in the marketplace.</p><p><strong>Contribution:</strong></p><p>This pre-study could be a good opportunity for the squash club’s management team to engage in marketing planning and develop its first marketing plan. Perhaps this study could also benefit other small sports clubs with similar challenges and give them ideas and new tools for future development, such as using on-line surveys.</p><p><strong>Suggested future research:</strong></p><p>It would be interesting to perform a comparison among the four racket sports: tennis, badminton, table-tennis and squash and the reasons behind young people choosing to play one sport over the others.The result would help racket clubs to better understand how they should position themselves in the market place to attract young people to their particular sport.</p>

Aim: The purpose was to perform a pre-study to marketing planning for a local squash club in Sweden that had difficulties with membership growth and development. This pre-study would provide the squash club with valuable information and a starting point when creating its first marketing plan. Method: The chosen research approach included theoretical and empirical studies. Empirical data was collected by triangulation, using both qualitative and quantitative methods. A semi-structured interview and two surveys using on-line questionnaires were conducted, analyzed and presented. The discussed theory including key definitions, models and concepts was related to the empirical data findings and reflected on. Results &amp; Conclusions: A small non-profit squash club with scarce resources and slim organization has to implement a customer centered mindset and work smarter instead of harder.It is important for the club to carefully match market opportunities with its objectives and capabilities.Engaging in marketing planning and the development of a marketing plan will enable the club to find new creative ways to offer a unique squash experience that will result in a positive membership development. Recommendations: The squash club should strive to develop key strategic partnerships that can compliment its strengths and help reduce its weaknesses.An own club website would improve internal and external communication significantly and decrease the club management’s administrative workload.It would be advisable for the club to perform annual online customer satisfaction surveys to monitor and measure own performance and detect key changes in the marketplace. Contribution: This pre-study could be a good opportunity for the squash club’s management team to engage in marketing planning and develop its first marketing plan. Perhaps this study could also benefit other small sports clubs with similar challenges and give them ideas and new tools for future development, such as using on-line surveys. Suggested future research: It would be interesting to perform a comparison among the four racket sports: tennis, badminton, table-tennis and squash and the reasons behind young people choosing to play one sport over the others.The result would help racket clubs to better understand how they should position themselves in the market place to attract young people to their particular sport.