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Idade e crescimento da pata-roxa Scyliorhinus canicula (Linnaeus, 1758) da costa sudoeste de Portugal
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Abstract(s)
A pata-roxa Scyliorhinus canicula é o membro mais abundante da família Scyliorhinidae
nas águas costeiras do Oceano Atlântico Nordeste. Embora seja um elasmobrânquio
bastante abundante e uma espécie acessória de diferentes pescarias, existe pouca
informação acerca da sua biologia nas águas de Portugal continental. A necessidade de
melhorar o conhecimento desta espécie motivou o estudo da idade e crescimento de
indivíduos capturados na costa portuguesa recorrendo, para tal, às suas vértebras. Foram
amostrados 116 indivíduos (69 machos e 47 fêmeas) com comprimentos totais entre 222 e
571 mm. De modo a possibilitar a contagem dos pares de bandas foram testadas duas
técnicas de limpeza das vértebras e três técnicas de enaltecimento das bandas de
crescimento. A combinação que produziu melhores resultados foi a limpeza com imersão em
NaClO e o enaltecimento através da descalcificação das vertebras com HNO3 (a 5%). As
idades máximas estimadas para machos e fêmeas foram de 12 e 11 anos, respetivamente.
Foram ajustados três modelos de crescimento: von Bertalanffy, von Bertalanffy com L0 fixo e
Gompertz. Todos os modelos sugerem que o crescimento das fêmeas e dos machos é
significativamente diferente. Este estudo providencia estimativas dos parâmetros de
crescimento de pata-roxa para as águas de Portugal continental, o que constitui um
importante contributo para a avaliação do estado da sua população.
ABSTRACT: The lesser-spotted dogfish Scyliorhinus canicula is the most abundant specie of the Scyliorhinidae family in the Northeast Atlantic Ocean coastal waters. Although it is an abundant elasmobranch and bycatch specie of different fisheries, little information exists about its biology in Portuguese continental waters. The need to improve the knowledge of this specie led to the age and growth study of individuals captured in the Portuguese coast, through vertebrae. In this work 116 specimens were sampled (69 males and 47 females) between 222 and 571 mm total length. To enable the counting of the band pairs in the vertebra centra, two cleaning techniques and three band enhancement techniques were tested. The combination that showed the best results was cleaning with NaClO and band enhancement through nitric acid decalcification. The maximum ages estimated for males and females were 12 and 11 years, respectively. Three growth models were adjusted in order to quantify the growth rate of this specie: von Bertalanffy, von Bertalanffy with fixed L0 and Gompertz. All the models suggest that the growth of females and males has significant differences. This study provides growth parameters estimations of lesser spotted dogfish to Portuguese continental waters, which is an important contribution to the assessment of the population condition.
ABSTRACT: The lesser-spotted dogfish Scyliorhinus canicula is the most abundant specie of the Scyliorhinidae family in the Northeast Atlantic Ocean coastal waters. Although it is an abundant elasmobranch and bycatch specie of different fisheries, little information exists about its biology in Portuguese continental waters. The need to improve the knowledge of this specie led to the age and growth study of individuals captured in the Portuguese coast, through vertebrae. In this work 116 specimens were sampled (69 males and 47 females) between 222 and 571 mm total length. To enable the counting of the band pairs in the vertebra centra, two cleaning techniques and three band enhancement techniques were tested. The combination that showed the best results was cleaning with NaClO and band enhancement through nitric acid decalcification. The maximum ages estimated for males and females were 12 and 11 years, respectively. Three growth models were adjusted in order to quantify the growth rate of this specie: von Bertalanffy, von Bertalanffy with fixed L0 and Gompertz. All the models suggest that the growth of females and males has significant differences. This study provides growth parameters estimations of lesser spotted dogfish to Portuguese continental waters, which is an important contribution to the assessment of the population condition.
Description
Dissertação de Mestrado apresentada no ISPA – Instituto Universitário para obtenção de grau de Mestre na especialidade em Biologia Marinha e Conservação
Keywords
Scyliorhinus canicula Portugal Vértebras Idade Modelos de crescimento Vertebrae Age Growth model