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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Factors influencing Kemp's ridley sea turtle (Lepidochelys kempii) distribution in nearshore waters and implications for management

Metz, Tasha Lynn 15 November 2004 (has links)
Post-pelagic juvenile and subadult Kemp's ridley sea turtles (Lepidochelys kempii) (20-40 cm straight carapace length) utilize nearshore waters of the northwestern Gulf of Mexico as nursery or developmental feeding grounds. This study utilizes 10 years of entanglement netting data to characterize long-term abundance and distribution of Kemp's ridley sea turtles at index habitats in this region. Netting surveys were conducted during April-October 1993-2002, primarily at Sabine Pass, Texas and Calcasieu Pass, Louisiana. Additionally, this study takes an ecosystem-based approach to understanding factors influencing Kemp's ridley in-water abundance and distribution via the development of a conceptual model incorporating data on nesting dynamics, environmental conditions, prey availability, and predation pressure. Overall monthly mean ridley catch-per-unit-effort (CPUE) peaked in the beginning of summer (April-June), probably in response to rising water temperatures and seasonal occurrence of blue crab prey. Annual mean ridley CPUE across all study areas peaked in 1994, 1997, 1999 and 2002, suggesting a 2-3 year cycle in abundance that may be related to patterns in clutch size or hatch success at the Rancho Nuevo, Mexico nesting beach. However, ridley CPUE in nearshore waters remained relatively constant or decreased slightly even as number of hatchlings released from Rancho Nuevo increased exponentially. Annual declines in Texas strandings since 1994 and subsequent increases in Florida counterparts since 1995 suggest a shift in ridley distribution from the western to eastern Gulf in recent years. Significant declines in ridley CPUE at Sabine Pass since 1997 coincided with a concurrent reduction in blue crab size, but a similar trend was not detected at Calcasieu Pass. Kemp's ridley occurrence at study sites was not significantly related to shrimping activity/by-catch. There also were no biologically significant relationships between Kemp's ridley CPUE and abiotic factors, nor were ridleys deterred from utilizing areas frequented by bull sharks. Overall, nesting dynamics and prey availability were conceptual model components appearing to have the greatest influence on nearshore ridley occurrence.
232

Diverzita zooplanktonu tatranských jezer v prostoru a čase / Diversity of zooplankton of Tatras lakes in space and time

Čablová, Radka January 2021 (has links)
This thesis is the first of its kind that evaluates the species composition, species richness and species abundance of zooplankton in littoral samples of 90 Tatras lakes (Western and High Tatras of Slovakia and Poland) collected in September 2004 in the context of environmental parameters of lakes and spatial relationships of individual lakes. The most frequently occurring species in the Tatras lakes in 2004 were also evaluated in terms of their occurrence in the lakes a century ago (Minkiewicz 1914, 1917 and Lityński 1913, 1917), during the period of acidification (Ertl & Vranovský 1964, Ertl et al. 1965, Hrbáček et al. 1974, Stuchlík et al. 1985) and during the period of recovery of the lakes from acidification (Hořická et al. 2006, Sacherová et al. 2006). Relationships between variables were analysed using Poisson regression, cluster analysis with multinomial regression, canonical correspondence analysis, Mantel tests and multiple negative binomial regression. Using analyses, lakes were divided into four clusters (A, B, C, D). Each cluster consisted of lakes with the same environmental and spatial factors and similar species composition. Thirteen zooplankton species (Acanthocyclops vernalis, Acroperus harpae, Alona affinis, Arctodiaptomus alpinus, Ceriodaphnia quadrangula, Cyclops abyssorum...
233

The temporal distribution and relative abundance of stable flies (Stomoxys calcitrans) (Diptera: Muscidae) in a feedlot near Heidelberg, Gauteng, South Africa / Maria Magdalena Evert

Evert, Maria Magdalena January 2014 (has links)
The stable fly, Stomoxys calcitrans (L.) is a haematophagous fly that feeds primarily on the forelegs of cattle stimulating a range of avoidance behaviours in confinement situations such as feedlots. From literature it is apparent that stable flies associated with feedlots have a significant impact on cattle especially with regard to economic parameters such as a decline in feed intake and thus a lower average daily gain resulting in less meat production due to irritation caused by painful bites. The abundance of the stable flies was studied in a large commercial feedlot near Heidelberg from October 2012 to September 2013. Two tsetse fly traps, namely the NZI and the Vavoua fly traps, were used and evaluated in determining the seasonal abundance of the stable flies. The tsetse traps proved to be most effective for sampling stable flies compared to other designs. The NZI and Vavoua tsetse type trap were compared and although there were no significant difference the NZI trap proved to be more reliable and user friendly for this study. Stable flies were more abundant from late December with a peak in numbers late in January through February and became less abundant from early March. Minimum to no fly abundance occurred in the winter months from May to June 2013. The data indicated a strong edge effect for the stable flies, the flies were more abundant in pens and corridors that were surrounded by vegetation, manure run off and holding ponds. The numbers collected in traps were correlated with stable fly counts on the cattle to be used in calculating a future threshold in chemical control. Preliminary observations on the influence of temperature, wind speed and rainfall were also made. This research will form part of a larger project to determine an integrated fly management program for the feedlot. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
234

The temporal distribution and relative abundance of stable flies (Stomoxys calcitrans) (Diptera: Muscidae) in a feedlot near Heidelberg, Gauteng, South Africa / Maria Magdalena Evert

Evert, Maria Magdalena January 2014 (has links)
The stable fly, Stomoxys calcitrans (L.) is a haematophagous fly that feeds primarily on the forelegs of cattle stimulating a range of avoidance behaviours in confinement situations such as feedlots. From literature it is apparent that stable flies associated with feedlots have a significant impact on cattle especially with regard to economic parameters such as a decline in feed intake and thus a lower average daily gain resulting in less meat production due to irritation caused by painful bites. The abundance of the stable flies was studied in a large commercial feedlot near Heidelberg from October 2012 to September 2013. Two tsetse fly traps, namely the NZI and the Vavoua fly traps, were used and evaluated in determining the seasonal abundance of the stable flies. The tsetse traps proved to be most effective for sampling stable flies compared to other designs. The NZI and Vavoua tsetse type trap were compared and although there were no significant difference the NZI trap proved to be more reliable and user friendly for this study. Stable flies were more abundant from late December with a peak in numbers late in January through February and became less abundant from early March. Minimum to no fly abundance occurred in the winter months from May to June 2013. The data indicated a strong edge effect for the stable flies, the flies were more abundant in pens and corridors that were surrounded by vegetation, manure run off and holding ponds. The numbers collected in traps were correlated with stable fly counts on the cattle to be used in calculating a future threshold in chemical control. Preliminary observations on the influence of temperature, wind speed and rainfall were also made. This research will form part of a larger project to determine an integrated fly management program for the feedlot. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
235

Spatial and Temporal Dynamics of Larval Fish Assemblages in the Strait of Georgia

Guan, Lu 30 April 2015 (has links)
For marine fishes, the early larval phase is considered a critical stage for survivorship and recruitment. The spatial and temporal dynamics of larval fish assemblages can influence their success and trophic structure of marine communities and entire ecosystems. This thesis will provide the first characterization of larval fish assemblage in the Strait of Georgia (SoG) in terms of diversity, abundance and composition, and their variability over multiple temporal scales, as well as the first quantification of variability in larval fish distribution in the SoG across multiple spatial scales. On the interdecadal scale, a significant decrease in larval abundance of several dominant fish taxa (Pacific hake, walleye Pollock, northern smoothtongue and rockfishes) contributed to a decline in total larval abundance and turnover in the composition structure between the early 1980s and the late 2000s. In contrast, both abundance and the relative composition of flatfishes and several demersal forage fish taxa increased during the same period. On interannual scales, abundance, diversity and community structure of the spring larval assemblages varied dramatically through 2007-2010, a period which alternated between strong La Niña and El Niño events. Higher overall larval concentrations were associated with warm conditions in the SoG in 2007 and 2010, while the lowest larval concentration was associated with cooler condition in 2009. Examination of associations between larval fish assemblages and environmental fluctuations suggests a potential influence of large-scale climate processes between the early 1980s and the late 2000s, but a primary association with local environmental factors on interannual scales. Spatial patterns in larval density of three dominant fish taxa (Pacific herring, Pacific hake and northern smoothtongue) were mostly structured on predefined broad (> 40km) and medium (20~40km) scales. Although their scale-dependent associations with environmental factors varied interannually, larval distributions in the central-southern SoG were generally associated with salinity, temperature and vertical stability of water column in the upper layer (0-50m). Our results emphasize the role of local estuarine circulation in structuring hierarchical spatial distributions of planktonic fish larvae in the SoG. These findings will provide considerable implications in fisheries resource management and conservation strategies. / Graduate / 0416 / 0329 / guanlu129@gmail.com
236

Landscape-scale effects of oil and gas development on grassland passerines in southern Alberta

Daniel, Jody 19 January 2016 (has links)
Agriculture and, more recently, oil and gas development have contributed to extensive degradation and loss of temperate grasslands. I investigated the landscape-scale effects of oil and gas development, and roads, on grassland birds in southern Alberta using abundance, clutch size and nesting success data collected from 2010-2014. I estimated: (i) the distance at which there are effects of edge, and effects of shallow gas well density, using piecewise regressions; (ii) the locations and extent of habitat affected by infrastructure for obligate grassland species– Baird’s Sparrow (Ammodramus bairdii), Chestnut-collared Longspur (Calcarius ornatus) and Sprague’s Pipit (Anthus spragueii); and generalist species – Clay-colored Sparrows (Spizella pallida), Horned Lark (Eremophila alpestris), Savannah Sparrow (Passerculus sandwichensis), Vesper Sparrow (Pooecetes gramineus) and Western Meadowlark (Sturnella neglecta), and (iii) the total area affected by wells and roads. My findings suggest that the effects of roads, overall, extended to further distances than edge effects associated with natural gas wells, obligate species had more habitat affected by infrastructure than generalist species and shallow gas wells affected more habitat than did oil wells, due to their greater density on the landscape. Additionally, obligates, on average, were negatively affected by proximity to edge where as generalists were more productivity closer to edge. Reducing fragmentation caused by roads, minimizing the spread of non-native vegetation and management of cattle around gas wells could improve habitat quality for these focal species. / February 2016
237

The Geology and Geochemistry of Beryllium in Southern Arizona

Balla, John Coleman January 1962 (has links)
Nine beryllium deposits were studied in order to determine the geological environment of beryllium mineralization in southern Arizona. Beryllium occurs in two pegmatite areas, two contact metamorphic deposits, two quartz-tungsten veins, two quartz-feldspar veins, and in one quartz monzonite stock. It is associated in almost all of these deposits with purple fluorite and tungsten. Beryllium mineralization is associated with granitic and quartz monzonite intrusions of Laramide age, and generally occurs at the intersection of northwest-trending lineaments and the Texas lineament.
238

Paukščių populiacijų gausos indekso naudojimas bioindikacijai Europos Sąjungoje / Use of bird population indices as biological indicators in the European Union

Platovienė, Teresa 29 June 2009 (has links)
Paukščiai laikomi gerais biologinės įvairovės ir aplinkos kokybės indikatoriais. Kasmetinės paukščių apskaitos vykdomos visose ES šalyse ir kai kuriuose kitose Europos valstybėse. Paukščių populiacijų gausos indeksai apjungia informaciją apie atrinktų paukščių rūšių populiacijų bendrus gausos pokyčius. Paukščių rūšys parenkamos atsižvelgiant į šalies paukščių rūšinę sudėtį. Europoje plačiausiai naudojami įprastų rūšių paukščių indeksai, kurie yra paremti paukščių populiacijų gausos pokyčių tendencijų vidurkio skaičiavimu. Jungtinės Karalystės ir Nyderlandų mokslininkai pirmauja skaičiuojant ir naudojant paukščių populiacijų indeksą biologinei inikacijai vertinti. Plačiai paplitusių ir įprastų miško paukščių populiacijų tendencijos rodo – kad jie visoje Europoje nežymiai nyksta. Agrarinio kraštovaizdžio paukščių populiacijų indeksai atskleidžia, kad Vakarų Europoje paukščių populiacijų sumažėja per pastaruosius 25 m. apie 40 proc., miškingo kraštovaizdžio- apie 20 proc., o dažnų paikščių populiacijų gausa beveik nepakyto. Surinkta po įvairius šaltinius išsibarščiusi informacija rodo, kad svarbiausia paukščių nykimo priežastis yra nepakankamai palanki žemės ir miškų ūkio politika. / Birds are considered as good biodiversity and environment quality indicators. Annual bird surveys are being performed in all European Union and in some other European countries. Bird population indices integrate information on changes of numbers of populations of selected species. National lists of the species to be used when calculating bird population indices are formed depending on country specific bird fauna. In Europe common bird indices are used most widely. They are based on calculation of average changes of local population numbers. Scientists of United Kingdom and the Netherlands are leading methodological studies when calculating bird population index with the goal of biological indication. Trends of the common forest bird populations show their insignificant decrease in all the Europe. During recent 25 years in West Europe indices of bird populations of high specialised species discover their big decrease (about 40 %) in agricultural landscape and reasonable decrease (about 20 %) in forest landscape. Meanwhile populations of very common non-specialised species have remained near stabile. Collected rather scare and dispersed scientific literature shows that not enough environmentally friendly agriculture and forestry have to be considered as a main reason of bird population decline in Europe.
239

Stream channelization effects on fish abundance and species composition

Johansson, Ulf January 2013 (has links)
Streams are important habitats, providing shelter and feeding opportunities for a wide range of organisms. The species depending on running waters includes a wide array of fish species, using these waters for their whole or parts of their lifecycle. Streams are also the subject of different anthropogenic impact, e.g. hydropower development. Hydropower development usually means lost connectivity, altered flow regimes and channelization. Channelization is one of the major factors causing stream habitat loss and degradation and thereby a threat to biodiversity of running waters. In the present study, the ecological impact of channelization on the fish fauna along a gradient of channelization severeness was examined. Besides channelization, stream velocity and depth were taken in to account. The study was carried out in two adjacent nemoboreal streams, Gavleån and Testeboån. The study was conducted between the 6th of June and the 10th of October 2012 at 15 sites. Sites were selected using historical maps and field observations and graded 0-3 depending on the degree of channelization. Fish community were sampled with, Nordic multi-mesh Stream Survey Net (NSSN). In all, 1.465 fish were captured, representing 15 species and seven families. The sites differed in species richness, abundance and proportion of individuals. Based on the results from rarefaction curves and ANOVA, channelization was found to be the main factor affecting the fish biota, both in abundance as well as species richness and composition. In general the rheophilic species declined along the gradient of increasing channelization severeness, while limnophilic species increased
240

Le Frein et l’aiguillon : éloquence musicale et nombre oratoire. Allemagne et Italie, 1600-1750 / The bit and the spur : musical eloquence and rhetorical number. Germany and Italy, 1600-1750

Sueur, Agathe 17 December 2011 (has links)
Cette thèse, motivée par les recherches récentes sur la « rhétorique musicale », étudie le nombre éloquent, notion aux nombreuses ramifications dans les domaines oratoire et poétique, encore peu examinée dans le champ musical. L’approche est philologique, comparatiste et historique, et vise à déterminer dans quelle mesure, entre 1600 et 1750, les modes d’approche et de perception du nombre en poésie et dans l’art oratoire ont eu leur équivalent en musique, en Italie (jésuite essentiellement) et en Allemagne. Après une mise en perspective de la culture des spécialistes de musique, partagée entre rhétorique scolaire et éloquence adulte, l’examen du découpage conceptuel opéré par les Anciens entre oratio vincta et soluta permet d’identifier des modes de composition, d’écoute et de prononciation du discours musical vocal et instrumental. La perception de la stricte récurrence propre à la musique métrique (vincta) contraste avec celle de la bigarrure variée de la musique « en prose » (soluta), et les approches érudites et néophytes diffèrent. Au plan micro-structurel, les périodes musicales sont abordées à l’instar des périodes oratoires. Selon qu’elles sont « arrondies » ou « articulées », elles mettent en œuvre le nombre grâce aux rythmes, à la conduite harmonieuse et à un travail de structuration par amplification. L’écriture périodique apparaît comme un principe fondamental de composition. La réflexion sur l’éloquence du nombre en musique s’inscrit finalement dans le débat touchant le meilleur style. Tenants de la brièveté musicale et partisans de l’abondance s’opposent, appliquant au domaine musical les réflexions sur le laconisme, l’atticisme et l’enflure. / This dissertation was undertaken in the wake of the recent research about musical rhetoric and focuses on the rhetorical number, a concept of acknowledged significance in the field of oratory and poetry that as yet has seldom been examined in the field of music. Following a philological, comparative and historical approach, the present study aims at determining to what extent the modes of perception and approach of the numerus in poetry and rhetoric had counterparts in music in Italy (mainly among the Jesuits) and Germany between 1600 and 1750. The study first deals with the culture of music specialists, which relates partly to scholastic rhetoric and partly to mature eloquence, and then investigates the conceptual division set by the Ancients between oratio vincta and soluta, so as to show that such division makes it possible to delineate the composition and listening and pronunciation processes of musical discourse, both vocal and instrumental. Perception of the strict recurrence that is specific to metrical music (vincta) contrasts with the heterogeneous variety of « prose »music (soluta) and it differs among scholars and novices. As for the microstructures of discourse, musical periods are tackled similarly to oratorical periods. Whether they are « rounded » or « articulated », they become rhythmical thanks to metrical feet or harmonious structure as well as processes of amplification. Periodical style appears fundamental to composition. The present dissertation eventually shows that the discussion of musical oratio numerosa is related to the impassioned debate over the best musical style (brevity, abundance, laconism, atticism and bombast).

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