Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2011. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-10-09T17:25:09Z No. of bitstreams: 1 Evandro.pdf: 2513898 bytes, checksum: 56564f2ddd5a85095a4f342776ac7ec9 (MD5) / Approved for entry into archive by Sabrina Andrade (sabrinabeatriz@ibest.com.br) on 2013-10-17T03:06:55Z (GMT) No. of bitstreams: 1 Evandro.pdf: 2513898 bytes, checksum: 56564f2ddd5a85095a4f342776ac7ec9 (MD5) / Made available in DSpace on 2013-10-17T03:06:55Z (GMT). No. of bitstreams: 1 Evandro.pdf: 2513898 bytes, checksum: 56564f2ddd5a85095a4f342776ac7ec9 (MD5) Previous issue date: 2011 / Os padrões associados às condições ambientais e a distribuição espaço-temporal dos estágios iniciais da savelha, B. pectinata, e de seu desenvolvimento no estuário da Lagoa dos Patos foram investigados através de dados históricos. Dois outros experimentos complementares foram realizados: um para avaliar as técnicas de medição (tradicional e por imagem) em larvas de peixes; e, outro, para investigar o efeito dos principais conservantes (álcool 70 % e formaldeído 3,6%) sobre as larvas de savelha. Diferença significativa na medição de larvas de peixes entre ambas as técnicas não foi observada, e os coeficientes de variação foram similares, o que sugere que as técnicas produzem o mesmo resultado médio, apesar do ganho de precisão pela técnica de análise por imagem. Um encolhimento significativo foi observado para ambos os conservantes, e os fatores de correção para as larvas de B. pectinata em formaldeído foi CP vivo = 1,0799 × CP pós-conservação, e em álcool foi CP vivo = 1,1415×CP pós-conservação. No período de 1975 a 2009, um total de 10479 ovos e 14066 larvas e juvenis foram coletados através de amostragens planctônicas, e também amostrados parâmetros da água (salinidade e temperatura). As larvas foram medidas e classificadas de acordo com seu estágio de desenvolvimento. Cada estágio de desenvolvimento foi caracterizado pelo seu intervalo de tamanho, onde a menor larva em estágio vitelínico mediu 2,16 mm, e o maior juvenil teve 43,25 mm. As análises dos padrões de distribuição indicam desova fora da Lagoa dos Patos, em salinidade mais elevada, sendo importantes períodos sazonais para os ovos o inverno, primavera e início de verão, e posteriormente ocorre um transporte para dentro da região estuarina nos estágios mais iniciais de desenvolvimento, associados a valores menores de salinidade e temperatura. A distribuição dos juvenis indicou um retorno para a região costeira, e neste estágio o outono foi um período muito importante. Estes resultados são importantes para o conhecimento desta espécie, e serão úteis para o planejamento no gerenciamento deste recurso. / Patterns associated to environmental conditions and to the spatial and temporal distributions of the early stages of Argentine menhaden, B. pectinata, and of its development in the Patos Lagoon estuary were investigated using historical records. Two other complementary experiments were performed: one to evaluate the measurement techniques (traditional and image) in larval fishes; and, other, to investigate the effect of main conservatives (alcohol 70 % and formaldehyde 3.6 %) over Argentine menhaden larvae. Significant difference in the measurement of fish larvae between techniques was not observed, and the coefficients of variation were similar, suggesting that these two techniques produce the same average result, despite the gain in precision by image analysis technique. A significant shrinkage was observed for both preservatives, and the correction factors for B. pectinata larvae in formaldehyde was SL live= 1.0799 × SL post-conservation, and in alcohol was SL live= 1.1415 × SL post-conservation. From 1975 to 2009 a total of 10479 eggs and 14066 fish larvae and juveniles were collected at plankton surveys, and sampled water parameters (salinity and temperature), too. Larvae were measured and classified according to their developmental stage. Each development stage was characterized by its size range, which the smallest yolk-sac larvae measured 2.16 mm, and the largest juveniles had 43.25 mm. Analysis of the distributional pattern indicate spawning outside the Patos Lagoon, in high salinities, being important seasonal period for the eggs the winter, spring and early summer, and after occur a transport to the inner estuarine region in the earlier developmental stages, associated to lesser temperature and salinity values. Distribution of juveniles indicated a return to the coastal region, and in this stage the autumn was a very important period. These results are important for knowledge this specie, and will be useful for planning the management of this resource.

Livestock grazing is the most important type of land-use in arid and semi-arid regions. In these regions, uncertain and highly variable climate conditions cause scarce and spatio-temporally variable resource availability. The major challenge to livestock grazing is the efficient utilisation of these resources without running the risk of degradation. Therefore, well adapted grazing strategies that consider both local environmental characteristics and the farmers' individual needs and perceptions are crucial for sustaining human livelihoods. Particularly, rotational grazing is presumed to render adaptation to spatio-temporal heterogeneities possible. A systematic investigation, however, that analyses the interrelations between the major components of rotational grazing systems on appropriate spatial and temporal scales was missing so far. This doctoral thesis investigates different management strategies for sustainable livestock grazing in semi-arid rangelands. Using an integrated modelling approach, it enters into the question: how to adapt grazing systems to spatio-temporal heterogeneous rangeland conditions, variable and changing climate conditions, and different individual needs and goals of livestock farmers? In order to address these issues, the taken approach tackles both methodical challenges and applied concerns. In the first part of this study, a generic modelling framework is developed that incorporates important components of grazing systems on appropriate spatial and temporal scales. To parameterise the model, a pattern-oriented approach is developed that uses qualitative patterns to derive a broad range of plausible parameter sets supporting a general model analysis. In the second part, a variety of management strategies is explored under different climatic, ecological, and economic conditions. The research focuses in particular on combined effects between and relative importance of different management components. The question how the results of different management strategies depend on the type of vegetation is investigated. Furthermore, the performance of rotational grazing strategies is analysed under different economic requirements and rainfall conditions. The study also identifies management strategies that are suitable to adapt a grazing system to spatio-temporally variable rangeland conditions. Overall, this thesis contributes to a general understanding of basic principles for adaptation to spatio-temporal heterogeneities as well as the interplay of different management components. The results allow an evaluation of management strategies for specific situations and the identification of strategies that are robust to a broad range of situations including different aspects of global change.