Obrigada ao Dr. Rui Coelho por ter aceite orientar este trabalho e por toda a ajuda imprescindível, assim como ao Dr. Karim Erzini. À Daniela Rosa, obrigada por toda a ajuda e pela paciência durante estes meses de trabalho, e também ao Rubén Muñoz-Lechuga pela sua disponibilidade. Obrigada aos observadores do IPMA, Carlos Barbosa e Sérgio Goes, que recolheram as amostras sem as quais esta tese não seria possível, e também à restante equipa do IPMA por me terem feito sentir integrada. Aos meus pais e à minha irmã, obrigada por terem estado sempre presentes mesmo quando eu não estava, e por todo o apoio incondicional. À minha restante família, um grande abraço e obrigada por tudo. Obrigada à Inês por estares presente em tudo quase desde sempre, à Mariana que chegaste mais tarde, mas para ficar para sempre e ao Diogo que mesmo quando estiveste longe estiveste sempre perto. To all the friends I met in Faro, but I feel like I have known for so long, thank you for making these two years so much fun even when times were harder. I wish you all the best.

the target species, they are frequently retained for their meat, fins, and jaws (Casey and Kohler, 1992; Babcock and Nakano, 2008). Although the species has long been considered vulnerable to overexploitation because of its late age at maturity, low reproductive potential, and commercial value (Dulvy et al., 2008; Cortés et al., 2010), catch levels were considered sustainable (ICCAT 2). However, the results of an electronic tagging study conducted in 2013-2015 2 ICCAT (International Commission for the Conservation of Atlantic Tunas). 2013. 2012 shortfin mako stock assessment and ecological risk assessment meeting (Olhão,

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The smooth hammerhead Sphyrna zygaena (Sphyrnidae) is a pelagic shark occasionally caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Age and growth of S. zygaena was studied along a wide Atlantic region covering both the north and south hemispheres. Data from 304 specimens, caught between October 2009 and September 2014, ranging in size from 126 to 253 cm fork length (FL), were analyzed. Growth models were fitted using the 3-parameter von Bertalanffy growth function (VBGF) re-parameterised to calculate L0 (size at birth). Growth models were fitted to the sample data and data from several backcalculation models. The model fit to the quadratic modified Dahl-Lea back-calculated data seems to be the most appropriate model to describe growth in this species, with resulting growth parameters of Linf = 285 cm FL, k = 0.09 year -1 for males and Linf = 293 cm FL, k = 0.09 year -1 for females. Compared to other species of the same genus, estimated growth coefficients for S. zygaena seem to fall in the low to middle range. Although further work is still needed, this study adds to knowledge of the vital life-history parameters of smooth hammerheads in the Atlantic Ocean, which can be used in this species' management and conservation.