DMTD Key Exploited Species as Surrogates for Coastal Conservation in an Oceanic Archipelago: Insights from topshells and limpets from Madeira (NE Atlantic Ocean) DOCTORAL THESIS Ricardo Jorge Silva Sousa DOCTORATE IN BIOLOGICAL SCIENCES May | 2019 Key Exploited Species as Surrogates for Coastal Conservation in an Oceanic Archipelago: Insights from topshells and limpets from Madeira (NE Atlantic Ocean) DOCTORAL THESIS Ricardo Jorge Silva Sousa DOCTORATE IN BIOLOGICAL SCIENCES Note: The present thesis presents the results of work already published (chapters 2 to 11), in accordance with article 3 (2) and article 6 (2) of the Specific Regulation of the Third Cycle Course in Biological Sciences of the University of Madeira. Resumo As lapas e os caramujos estão entre os herbívoros mais bem adaptados ao intertidal do Atlântico Nordeste. Estas espécies-chave fornecem serviços ecossistémicos valiosos, desempenhando um papel fundamental no equilíbrio ecológico do intertidal e têm um elevado valor económico, estando sujeitas a altos níveis de exploração e representando uma das atividades económicas mais rentáveis na pesca de pequena escala no arquipélago da Madeira. Esta dissertação visa preencher as lacunas existentes na história de vida e dinâmica populacional destas espécies, e aferir os efeitos da regulamentação da apanha nos mananciais explorados. A abordagem conservacionista implícita ao longo desta tese pretende promover: (i) a regulamentação adequada da apanha de caramujos (Phorcus sauciatus) e (ii) a avaliação dos efeitos da regulamentação da apanha de lapas nas populações exploradas (Patella aspera, Patella candei). Atualmente, os mananciais de lapas e caramujos são explorados perto do rendimento máximo sustentável, e a monitorização e fiscalização são fundamentais para evitar a futura sobre-exploração. A regulamentação da apanha de lapas produziu um efeito positivo nas espécies de lapas exploradas, com um aumento no tamanho, na proporção de indivíduos reprodutores, no tamanho de maturação e num maior equilíbrio na proporção de sexos. A apanha de caramujos não está regulamentada e com o atual nível de exploração ocorrem alterações na estrutura de tamanhos, abundância e potencial reprodutivo das populações exploradas, pelo que urge implementar a regulamentação da apanha desta espécie, por forma a mitigar os efeitos negativos desta atividade. O efeito da proximidade das populações humanas e acessibilidade costeira na estrutura de tamanhos e abundância de gastrópodes explorados mostrou que a proporção de reprodutores e a abundância eram geralmente menores em áreas mais próximas das populações humanas e em áreas mais acessíveis. Os efeitos das Áreas Marinhas Protegidas na proteção das populações de lapas resultaram num aumento diferencial do tamanho, da maturidade sexual e da captura por unidade de esforço de acordo com o grau de proteção. O esclarecimento e envolvimento das comunidades locais, reguladores, decisores políticos e partes interessadas, baseados em informação e educação, são cruciais para uma gestão eficaz e sustentável destes gastrópodes marinhos e ecossistemas a médio e longo prazo. Palavras-chave Caramujos, Phorcus sauciatus, lapas, Patella aspera, Patella candei, Patella piperata, parâmetros biológicos, estrutura populacional, regulamentação, Áreas Marinhas Protegidas, exploração sustentável, intertidal, Arquipélago da Madeira, Atlântico Nordeste. I Abstract Limpets and topshells are among the most successful intertidal grazers in the North-eastern Atlantic. These keystone species play a pivotal role in structuring rocky shores communities, and provoding valuable ecosystem services. Than have an important economic value, being subject to high levels of exploitation and representing one of the most profitable economic activities in small-scale fisheries in the archipelago of Madeira. This thesis aims to fill the gaps on the life-traits and population dynamics of these species, and assess the effects of harvesting regulations on the exploited stocks. A focus on conservation is implicit throughout this thesis since it addresses the promotion of: (i) proper regulation of the unregulated harvesting of topshells (Phorcus sauciatus) and (ii) provide additional information on the effects of harvesting regulations on limpets (Patella aspera, Patella candei). Currently, limpets and topshells stocks are being exploited near the maximum sustainable yield and monitoring and enforcement must be accomplished to avoid future overexploitation. Conservation measures prompted a positive effect on both exploited limpet species with an increase in length, reproductive individuals, size-at-first maturity and a more balanced sex-ratio after harvesting regulations. The harvesting of topshells is not regulated and with the current level of exploitation there are changes in the size structure, abundance and reproductive potential of the exploited populations, so it is imperative to implement the harvesting regulations for this species, in order to mitigate the negative effects of harvesting. The effect of proximity to human settlements and coastal accessibility on the size-structure and abundance of exploited gastropods showed that the mean-size, proportion of reproductive individuals and abundance were generally smaller in areas closer to human settlements and in more accessible areas. The effects of protection from the Marine Protected Areas on limpet populations resulted in a differential increase on size, size-at-first maturity and catch-per-unit-effort according to the degree of protection. The understanding and commitment of local communities, regulators, policymakers and stakeholders, based on information and education are crucial to the effective management and to ensure the sustainability of these marine gastropods and ecosystems at medium and long term. Keywords Topshells, Phorcus sauciatus, limpets, Patella aspera, Patella candei, Patella piperata, life-traits, population structure, harvesting regulations, Marine Protected Areas, sustainable exploitation, intertidal, Madeira archipelago, North-eastern Atlantic. II Acknowledgements The success of this dissertation is the result of continuous work and perseverance and its accomplishment was only possible through the collaboration of numerous people, to which I express my deep gratitude: - To Dr. João Delgado for receiving me in the Research Service Directorate of the Regional Fisheries Department and for his constant support, availability, helpful assistance, and for providing logistical and human conditions; - To Paulo Henriques and Joana Vasconcelos for their constant help, encouraging spirit, suggestions and pertinent observations; - To Professor Rodrigo Riera (Universidad Católica de la Santísima Concepción, Chile) for his tireless collaboration, availability, guidelines, suggestions and corrections; - To Professor Stephen J. Hawkins (University of Southampton) for sharing his immense knowledge and for all the suggestions and assistance; - To Professor José António González (Universidad de Las Palmas de Gran Canaria) for is helpful assistance and constructive suggestions; - To André Pinto, Jorge Lucas, Filipe Andrade and Drª Mafalda Freitas for their participation, support and help in surveys; - To Drª Ana Rita Pinto, Drª Antonieta Amorim, Drª Graça Faria and Drª Lídia Gouveia for their cooperation, patience and support in overcoming numerous obstacles through this research; - To my family for the unconditional support throughout this thesis and my life in general; - To Research Service Directorate of the Regional Fisheries Department of Madeira (DSI/DRP). - To Regional Agency for the Development of Research, Technology and Innovation (ARDITI) and Oceanic Observatory of Madeira (OOM) for the financial support for my research through the fellowship ARDITI OOM/2016/010 (M1420-01-0145-FEDER-000001-Observatório Oceânico da Madeira-OOM); - To Institute of Forests and Nature Conservation (IFCN IP-RAM) for allowing the collection of specimens in Marine Protected Areas; - To the technicians of Research Service Directorate of the Regional Fisheries Department for their help in biological sampling. III Contents Resumo .................................................................................................................................................... I Palavras-chave ......................................................................................................................................... I Abstract ................................................................................................................................................... II Keywords ................................................................................................................................................ II Acknowledgements ............................................................................................................................... III PART I – GENERAL INTRODUCTION ........................................................................................................ 1 CHAPTER 1 – GENERAL INTRODUCTION ............................................................................................. 2 Introduction .................................................................................................................................... 3 Aims................................................................................................................................................. 9 Thesis outline and structure ........................................................................................................