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Efeito do tipo de anzol nas capturas acessórias de tartaruga comum, Caretta caretta (Linnaeus, 1758) nas pescas de palangre de superfície dos Açores
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Abstract(s)
Atualmente, as capturas acessórias são uma das principais ameaças antropogénicas nos sistemas marinhos e afetam muitas populações de animais, como por exemplo as tartarugas comuns. Nas águas dos Açores, maioritariamente utilizadas pelos juvenis de tartaruga comum, este tipo de pesca é dirigido ao espadarte e tintureira.
Os dados deste estudo foram recolhidos durante uma experiência de modificação de parâmetros na pesca de palangre, entre 2000 e 2004 (entre os meses julho e dezembro). Foram capturadas 491 tartarugas comuns em 335 lances de pesca. Os resultados mostraram que um maior número de capturas ocorre nos meses de agosto e setembro, sugerindo um padrão de sazonalidade na distribuição das tartarugas. Foi ainda possível concluir que o tipo de anzol tem uma influência significativa na captura de tartarugas, sendo o anzol RT o que obteve uma maior taxa de captura e os anzóis CLP18O, CLP18 e JM9O os que estiveram associados a menores taxas de captura. Os resultados mostraram um efeito significativo do tipo de anzol relativamente ao local do corpo onde ficou ferrado e os anzóis circulares tiveram uma maior tendência para ficar ferrados na boca ou externamente do que na garganta, comparativamente aos anzóis “J”. Em relação ao tamanho das tartarugas capturadas, verificou-se que a arte de pesca é seletiva, com preferência por indivíduos de maiores dimensões (média> 50 cm CCL para todos os anzóis). Assim, modificações na arte de pesca parecem ter potencial para reduzir a captura acidental de tartarugas, mas a implementação de alterações no aparelho devem ser efetuadas com precaução
Currently, bycatch is one of the main anthropogenic threats on marine systems worldwide and affect many animal populations, such as loggerhead turtles. In Azorean waters, mainly used by loggerhead juveniles, this type of fishing targets swordfish and dyer. The data of this study were collected during a longline gear modification experiment, between 2000 and 2004 (from July to December). 491 common turtles were caught in 335 fishing sets. The results showed that the great majority of catches occur in August and September, suggesting a seasonal pattern in the distribution of turtles. It was also possible to conclude that the type of hook has a significant influence on the catch rate of turtles, with the RT hook associated with a higher catch rate and CLP18O, CLP18 and JM9O hooks associated with lower ones. A significant effect of the hook type regarding the body location was also found, with circular hooks having a greater tendency to be hooked in the mouth or externally rather than in the throat, compared to “J" hooks. Regarding the size of the turtles captured, the fishing gear is selective, with preference for larger individuals (mean> 50 cm CCL for all hooks). Thus, modifications in the fishing gear seem to have potential to reduce turtles’ bycatch. Nevertheless, the implementation of changes should be carried out with caution. Keywords: loggerhead turtle,
Currently, bycatch is one of the main anthropogenic threats on marine systems worldwide and affect many animal populations, such as loggerhead turtles. In Azorean waters, mainly used by loggerhead juveniles, this type of fishing targets swordfish and dyer. The data of this study were collected during a longline gear modification experiment, between 2000 and 2004 (from July to December). 491 common turtles were caught in 335 fishing sets. The results showed that the great majority of catches occur in August and September, suggesting a seasonal pattern in the distribution of turtles. It was also possible to conclude that the type of hook has a significant influence on the catch rate of turtles, with the RT hook associated with a higher catch rate and CLP18O, CLP18 and JM9O hooks associated with lower ones. A significant effect of the hook type regarding the body location was also found, with circular hooks having a greater tendency to be hooked in the mouth or externally rather than in the throat, compared to “J" hooks. Regarding the size of the turtles captured, the fishing gear is selective, with preference for larger individuals (mean> 50 cm CCL for all hooks). Thus, modifications in the fishing gear seem to have potential to reduce turtles’ bycatch. Nevertheless, the implementation of changes should be carried out with caution. Keywords: loggerhead turtle,
Description
Dissertação de mestrado apresentada no ISPA – Instituto Universitário para obtenção de grau de Mestre na especialidade de Biologia Marinha e Conservação.
Keywords
Tartaruga comum Palangre de superfície Capturas acidentais Taxas de captura Anzóis circulares Loggerhead turtle Pelagic longline Bycatch Catch rate Circle hooks