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Publication
Contribuição para o conhecimento da espécie Scyliorhinus canicula através de observações na zona costeira de Cascais (Portugal) e em cativeiro
Abstract(s)
Apesar de se encontrar actualmente fora de perigo, a espécie Scyliorhinus canicula é alvo directo de pescas e importante constituinte de bycatch, o que, aliado ao papel que desempenha nos ecossistemas como topo da cadeia alimentar, faz com que seja relevante estudar esta espécie e compreender não só questões mais complexas, como também as informações biológicas básicas.
Neste trabalho teve-se como objectivo estudar a ocorrência de tubarões na costa de Cascais de forma a recolher informações biológicas e ecológicas relevantes, aliando a isto a recolha de dados quer em cativeiro, no Aquário Vasco da Gama, quer através de pesquisa em literatura, relacionando-os e oferecendo desta forma uma contribuição ao estudo da espécie que pode representar o inicio para futuros estudos na zona costeira de Cascais e resultar em informações interessantes tanto para aspectos de aquariologia como para o conhecimento da situação da espécie em Portugal.
Para isso realizaram-se observações em meio natural através de mergulhos em que se procurou recolher informações para responder a questões unicamente relativas a este meio. Entre as quais o mapeamento da ocorrência e mensuração da densidade, a obtenção de dados sobre a espécie na costa de Cascais e a exploração da possibilidade de haver diferenças na ocupação entre sexos.
Dados recolhidos em meio natural foram ainda relacionados com outros recolhidos através de observações em cativeiro para analisar objectivos mistos como a descrição e comparação de comportamentos e a análise dos padrões de comportamento nos dois meios.
Já os dados recolhidos em cativeiro também serviram para uma análise exclusiva de objectivos de meio artificial: comparar a reprodução em cativeiro com descrita na literatura, analisar a hipótese de segregação sexual por agressividade na reprodução, assim como os padrões de agressividade em cativeiro e procurar evidências da ocorrência de eletrorecepção em cativeiro.
Por fim, para compreender melhor a situação da espécie no nosso país, fez-se ainda um levantamento da ocorrência e estatísticas desta em Portugal e da sua utilização tradicional.
Despite being currently out of danger, the specie Scyliorhinus canicula is a direct target of fisheries and an important constituent of bycatch, which, together with its role in ecosystems as the top of the food chain, makes it relevant to study this specie and understand not only more complex issues but also basic biological information. The objective of this work was to study the occurrence of sharks on the coast of Cascais in order to collect relevant biological and ecological information, in addition to collecting data either in captivity, at the Vasco da Gama aquarium, or through research in literature, linking them and thus offering a contribution to the study of the species that may represent the beginning for future studies in the coastal zone of Cascais and result in interesting information both for aspects of aquariology and for the knowledge of the situation of the specie in Portugal. For this, observations were made in natural environment through dives in which information was collected to answer questions solely related to this environment. Among them were the mapping of the occurrence and density measurement, the obtaining of data about the specie on the coast of Cascais and the exploration of the possibility of differences in the occupation between sexes. Data collected in the natural environment were also related to others collected through captive observations to analyse mixed objectives such as the description and comparison of behaviours and the analysis of patterns of behaviour in the two environments. The data collected in captivity also served for an exclusive analysis of objectives of artificial environment: to compare the reproduction in captivity with described in the literature, to analyse the hypothesis of sexual segregation by aggressiveness in the reproduction, as well as the patterns of aggressiveness in captivity and to look for evidences of the occurrence of electroreception in captivity. Finally, to better understand the situation of the specie in our country, a survey was also made of the occurrence and statistics of this specie in Portugal and its traditional use.
Despite being currently out of danger, the specie Scyliorhinus canicula is a direct target of fisheries and an important constituent of bycatch, which, together with its role in ecosystems as the top of the food chain, makes it relevant to study this specie and understand not only more complex issues but also basic biological information. The objective of this work was to study the occurrence of sharks on the coast of Cascais in order to collect relevant biological and ecological information, in addition to collecting data either in captivity, at the Vasco da Gama aquarium, or through research in literature, linking them and thus offering a contribution to the study of the species that may represent the beginning for future studies in the coastal zone of Cascais and result in interesting information both for aspects of aquariology and for the knowledge of the situation of the specie in Portugal. For this, observations were made in natural environment through dives in which information was collected to answer questions solely related to this environment. Among them were the mapping of the occurrence and density measurement, the obtaining of data about the specie on the coast of Cascais and the exploration of the possibility of differences in the occupation between sexes. Data collected in the natural environment were also related to others collected through captive observations to analyse mixed objectives such as the description and comparison of behaviours and the analysis of patterns of behaviour in the two environments. The data collected in captivity also served for an exclusive analysis of objectives of artificial environment: to compare the reproduction in captivity with described in the literature, to analyse the hypothesis of sexual segregation by aggressiveness in the reproduction, as well as the patterns of aggressiveness in captivity and to look for evidences of the occurrence of electroreception in captivity. Finally, to better understand the situation of the specie in our country, a survey was also made of the occurrence and statistics of this specie in Portugal and its traditional use.
Description
Dissertação de Mestrado apresentada no ISPA - Instituto Universitário na área de Biologia Marinha e Conservação
Keywords
Scyliorhinus canicula Pata-roxa Comportamento Meio natural Cativeiro Small-spotted catshark Behaviour Natural environment Captivity