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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.
1

Brevetoxins in marine birds: Evidence of trophic transfer and the role of prey fish as toxin vector

Van Deventer, Michelle 01 June 2007 (has links)
Harmful algal blooms (HABs) of the brevetoxin-producing dinoflagellate Karenia brevis occur periodically along the central west coast of Florida. Mass mortalities of marine birds have long been associated with these blooms, yet there is little data documenting the accumulation of brevetoxins in the tissues of birds and their prey items. An intense HAB event impacted the region from Tampa Bay to Charlotte Harbor during most of 2005. More than one hundred marine birds, representing twenty three species, were collected during this bloom. All birds sampled were found dead or had died within 24 hours of admittance to local wildlife rehabilitation centers. In order to determine if fish were vectors for brevetoxin ingestion, the stomach contents of all birds were examined and any recovered fish were identified to the extent possible. The gastrointestinal tissues and contents from all avian samples were analyzed for brevetoxin levels, with results ranging from Shorebirds and gulls may also be exposed to brevetoxins via scavenging of red tide-killed fish deposited on beaches during blooms. Samples from scavenged fish were found to have brevetoxin levels ranging from 31 to 95,753 ng PbTx per gram tissue.
2

Seletividade da rede-de-espera utilizada na captura da sardinha-bandeira, Opisthonema oglinum (Lesueur, 1818) / Selectivity of drift nets used for catching the Atlantic thread-herring, Opisthonema oglinum (Lesueur, 1818)

SebastiÃo Ribeiro DÂAlva Teixeira 20 March 2015 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / A sardinha-bandeira, Opisthonema oglinum, pertence à famÃlia Clupeidae da ordem Clupeiformes sendo uma das cinco espÃcies do gÃnero Opisthonema. No Estado do Cearà sua captura se estende ao longo de toda a costa, durante todo o ano, com as melhores pescarias ocorrendo entre maio e dezembro. O presente trabalho teve como objetivo determinar a estrutura da populaÃÃo, a relaÃÃo peso/comprimento da sardinha-bandeira e a seletividade das redes-de-espera utilizadas na sua captura na Praia da Caponga, municÃpio de Cascavel, CearÃ, Brasil. Os dados de comprimento total (cm) e peso individual (g) foram obtidos de dois grupos, cada um com 780 indivÃduos, capturados por redes-de-espera com malhas de 5 cm e 6 cm entre nÃs opostos, no perÃodo de agosto a outubro de 2014. Esses dados foram descritos em histogramas de frequÃncia de comprimento e peso, sendo mais representativas as classes de 21,6 cm (24,23%) e de 87,0 g (32,31%) para a malha de 5 cm e de 25,7 cm (23,08%) e de 117,9 g (26,03%), para a de 6 cm. Quando todos os indivÃduos foram reunidos em um Ãnico grupo (1.560), sem distinÃÃo do tamanho da malha, as classes mais representativas foram a de 23,0 cm de comprimento (18,59%) e a de 105,5 g de peso (20,38%). As equaÃÃes que representaram as relaÃÃes peso/comprimento foram as seguintes: y=0,016 x^2,7636 (780 indivÃduos capturados com a malha de 5 cm); y=0,031 x^2,5635 (780 indivÃduos capturados com a malha de 6 cm); e y=0,021 x^2,6828 (1.560 indivÃduos). Para o estudo da seletividade foram analisados todos os exemplares de sardinha-bandeira (1.560) capturados com as redes-de-espera de malha de 5 cm e 6 cm. O comprimento mÃdio de seleÃÃo foi de 23,7 cm para a malha de 5 cm e de 28,5 cm para a de 6 cm. A amplitude de seleÃÃo foi de 23,7  7,9 cm e de 28,5  7,9 cm para as malhas de 5 cm e 6 cm, respectivamente. As equaÃÃes das curvas de seleÃÃo das redes-de-espera para os dois tamanhos de malha foram obtidas, e a probabilidade de capturar indivÃduos com comprimento inferior ao mÃnimo, estabelecido em 15 cm, foi muito baixa e correspondeu a 1,32% e 0,03% para as malhas de 5 cm e de 6 cm, respectivamente. Esta informaÃÃo à de grande valia para a manutenÃÃo do estoque da sardinha-bandeira capturada na Praia da Caponga, CearÃ. / Atlantic thread-herring, Opisthonema oglinum, belongs to the family Clupeidae and to the order Clupeiformes. It is one of the five species of the genus Opisthonema. In the state of CearÃ, it is caught along the entire coast, throughout the year, with the best fisheries occurring between May and December. This work aimed to study the population structure, the length/weight relationships of the Atlantic thread-herring and to determine gear selectivity of drift nets used for catching them in Caponga Beach, Cascavel, CearÃ, Brazil. Data of total length (cm) and individual weight (g) were obtained from two groups, each with 780 individuals captured by drift nets with meshes of 5 cm and 6 cm, from August to October 2014. These data are showed as histograms. The most representative classes of length and weight were 21.6 cm (24.23%) and 87.0 g (32.31%) for 5 cm mesh, while for the 6 cm mesh, the main classes were 25.7 cm (23.08%) and 117.9 g (26.03%). When all data was combined into a single group (1,560), without the mesh size distinction, the most representative classes were 23.0 cm long (18.59%) and 105.5 g in weight (20.38%). The equations representing the weight/length ratios were as follows: y=0.016 x^2.7636 (780 individuals captured with a mesh of 5 cm); y=0.031 x^2.5635 (780 individuals caught with a mesh of 6 cm); and y=0.021 x^2.6828 (1,560 individuals). To study the selectivity, 1,560 Atlantic thread-herring specimens captured with drift nets of 5 cm and 6 cm were analyzed. The selection mean length was 23.7 cm for 5 cm mesh and 28.5 cm for 6 cm mesh. The range of selection was 23.7  7.9 cm and 28.5  7.9 cm for 5 cm mesh and 6 cm mesh, respectively. The equations of the selection curves for the two mesh sizes were obtained, and the probability of capturing individuals with length less than the established minimum of 15 cm was very low, amounting to 1.32% and 0.03% for the meshes of 5 cm and 6 cm, respectively. This information is of great value to maintain the stock of Atlantic thread-herring in Caponga Beach, CearÃ.

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