UNIVERSIDADE do ALGARVE Faculdade de Ciências e Tecnologia Bioecology and Movement Patterns of Sharks off Recife, Brazil: Applications in the Mitigation of Shark Attack Hazard Thesis for the degree in Doctor of Philosophy in Marine, Earth and Environmental Sciences, specialty in Marine Ecology André Sucena Afonso − 2013 − UNIVERSIDADE do ALGARVE Faculdade de Ciências e Tecnologia Bioecology and movement patterns of sharks off Recife, Brazil: applications in the mitigation of shark attack hazard Bioecologia e padrões de movimentação de tubarões na costa de Recife, Brasil: aplicações na mitigação do risco de ataque Thesis for the degree in Doctor of Philosophy in Marine, Earth and Environmental Sciences, specialty in Marine Ecology Tese de Doutoramento em Ciências do Mar, da Terra e do Ambiente, ramo de Ciências do Mar, especialidade de Ecologia Marinha André Sucena Afonso Thesis supervised by: Tese orientada por: Prof. Doutor Fábio H. V. Hazin Prof. Doutor Karim Erzini − 2013 − Shark image in the cover by Anthony Kekona; Retrieved from www.kekonaart.com, with permission. Dedico esta tese aos meus pais. Nunca teria chegado até aqui sem o vosso primeiro empurrão. Abstract An abnormally high rate of shark attacks on humans off Recife, Brazil prompted the development of a shark monitoring program aiming at mitigating shark peril. Bottom longlines and drumlines were used as fishing gears and optimized for increasing selectivity towards large sharks and reducing fishing mortality. The fishing methodology allowed to reduce the shark attack rate considerably and to generate important bioecological information on tiger and bull sharks, species which seem to be responsible for most of the attacks. Tiger sharks in this region move preferentially to the north through wide home ranges. The presence of a port complex to the south of Recife could be attracting tiger sharks shoreward, which would subsequently visit the littoral of Recife due to their natural movements. Other important, site- specific features such as the presence of an estuary and an alongshore channel close to the beach, together with high pollution and siltation levels, could further promote the high risk of shark attack in the area. Tiger sharks use the continental shelf off northeastern Brazil mostly during early juvenile stages, where they quickly grow between January and September before departing to oceanic waters. Larger tiger sharks use deep oceanic waters more often but they frequently visit nearshore waters, probably in search for prey. The depth distribution of tiger sharks seems to correlate with both diel and lunar cycles, and abundances off Recife were correlated with month, lunar phase, tidal amplitude, pluviosity and wind direction. This information could be useful in determining periods when tiger sharks are more likely to occur in the area of risk. Compared to traditional shark-meshing programs, which produce a considerable amount of bycatch and fishing mortality, the methodology herein reported provides an effective solution to increase user safety at local beaches with minimal ecological consequences. Key-words: bycatch, coastal management, fishing mortality, longline, selectivity, shark attack mitigation, telemetry 5 Resumo Um surto de ataques de tubarão verificado na costa de Recife, Brasil, levou à instauração de um programa de monitorização de tubarões com o intuíto de mitigar o risco de ataques. Os equipamentos de pesca utilizados corresponderam a palangres de fundo e linhas de pesca, os quais foram optimizados tendo em vista a maximização da selectividade dirigida a tubarões potencialmente agressivos e a minimização da mortalidade por pesca. A presente metodologia possibilitou uma considerável redução da taxa de ataques de tubarão, ao mesmo tempo que permitiu a recolha de dados importantes sobre a bioecologia das espécies envolvidas nos ataques. Os tubarões tigre e buldogue são aparentemente responsáveis pela maioria dos incidentes. Nesta região, os tubarões tigre deslocam-se preferencialmente para norte e alcançam consideráveis distâncias. A presença de um complexo portuário a sul de Recife parece contribuir para atrair tubarões para áreas costeiras, os quais se deslocariam, consequentemente, para o litoral de Recife. Algumas características do litoral de Recife, tais como a presença de um estuário e de um canal paralelo à linha de costa, juntamente com elevados níveis de poluição e turbidez da água, poderão potenciar o risco de ataque. O tubarão tigre utiliza a plataforma continental do nordeste brasileiro maioritariamente durante o início da fase juvenil, crescendo rapidamente entre os meses de Janeiro e Setembro e partindo em seguida para águas oceânicas. Os espécimes mais velhos utilizam águas profundas do ambiente oceânico mas visitam frequentemente a plataforma continental, provavelmente em busca de presas. A distribuição vertical do tubarão tigre parece correlacionar-se com ambos os ciclos circadiano e lunar, e a sua abundância no litoral de Recife foi correlacionada com o mês, a fase lunar, a amplitude da maré, a pluviosidade e a direcção do vento. Esta informação poderá ser útil para definir os períodos em que a presença de tubarões tigre na área de risco é mais provável. Em comparação com os programas de emalhamento de tubarões tradicionalmente conduzidos, esta metodologia apresenta-se como uma solução eficaz para aumentar a segurança balnear, simultaneamente assegurando a minimização do impacto ecológico local. Palavras-chave: captura incidental, gestão costeira, mortalidade por pesca, palangre, selectividade, mitigação de ataques de tubarão, telemetria 6 Acknowledgments Agradecimentos During the past four years, many people and institutions contributed in diverse ways to this thesis. The aims of this study could not be at all accomplished if it hadn't been for them. I would like to acknowledge everyone who was involved, in particular: My supervisor in Brazil, Fábio Hazin, for opening the doors of his lab and trusting me with the execution of such a complex project. Thank you for believing in me and sharing your knowledge and wisdom, which so much helped improving this thesis. My supervisor in Portugal, Karim Erzini, for both the inestimable guidance at crucial moments and all the constant support overseas. Thank you for often being my lighthouse during this long odyssey. Dr. Barbara Block, from the Hopkins Marine Station (HMS) at the University of Stanford. Thank you so much for welcoming me at your lab and allowing me to join the white shark expedition to the Farallon Islands. I learned a lot from my experience in Monterey and I long to come back. Also from HMS, I am in debt to Salvador Jorgensen and Michael Castleton for spending so much time with me and teaching me the essentials about shark tagging. Thank you for sharing your knowledge and friendship, you have surely made my time in Monterey that much better. The Laboratório de Tecnologia Pesqueira (LATEP) and all the wonderful people that compose it. I am greatly thankful to Rafael (Brutos) Muniz for providing the logistic support, and to Luciana Ferreira and Pedro Castilho for their help on field and lab work. Many thanks to all the dozens of interns who assisted with field work, I will not refer to anyone in particular for space saving but this study would not have been possible without you. Hopefully, our paths will cross again in the future. 7 The Laboratório de Oceanografia Pesqueira (LOP) and all the people in it, particularly Paulo Oliveira, Alessandra Fischer and Elizabeth Cavalcanti who frequently helped with messy biological sampling. Obrigado por esta temporada maravilhosa, galera! I am deeply thankful to Bruno Macena for all the discussions about telemetry and marine science in general. We spent long, stubborn hours together figuring out how to operate unfamiliar techonologies, and I will never forget his friendship. Thank you as well to Zeca (Careca) Pacheco, Humberto Hazin and Diogo Nunes for their support, enthusiasm, and friendship. We shall meet plenty of times in the future. Prof. Rosangela Lessa, to whom I am grateful for the wonderful professional relationship and the opportunity to learn from her expertise. Moreover, the precious help of Francisco Mercante and Rodrigo Barreto on the analysis of shark vertebrae is also acknowledged. I am also grateful to Prof. Doctor Humber Agrelli, who helped me to understand predictive modeling better. Thank you for your endless patience and willingness to teach. The precious help provided by Nuno Queiroz regarding the Split Moving Window Analysis procedure is deeply acknowledged. The Instituto Oceanário de Pernambuco, particularly its president, Alexandre Carvalho, is also acknowledged for providing precious assistance in administrative work and for sharing the same concerns and phylosophies regarding shark attacks. The Departamento de Pesca e Aquicultura from the Universidade Federal Rural de Pernambuco, all its professors, students and staff, thank you for the great hospitality and the joyful time along these years. O meu mais sentido agradecimento ao povo Pernambucano; com ele aprendi a juntar lama e caos para fazer arte, e a minha vida então se transformou. Bem hajam! 8 Preface on thesis style Prefácio sobre o estilo da tese This thesis comprises eight chapters, a general conclusion, a list of bibliographic references, and supplementary tables and figures. The first chapter includes a general introduction to the subject of the thesis, and provides background information on sharks, shark attacks, and the specific