Socio-ecological indicators for sustainable management of global marine biodiversity conservation using sharks as a model species

Abstract

Global biodiversity is disappearing at an unprecedented rate; sharks are currently among the most threatened vertebrate groups with widespread overexploitation leaving 31% of all species at risk of extinction. Since 2009, 17 coastal nations have adopted a precautionary approach banning all commercial shark fishing. However, evaluating effectiveness of these ‘shark sanctuaries’ is impeded by a lack of robust data. Evidence-based conservation urgently requires data against which socio-ecological change can be measured to assess efficacy of policy and management interventions. This thesis takes an interdisciplinary approach to advance understanding of the complexities of shark conservation within one of the world’s principal shark sanctuaries - the Maldives. Historical abundance trends derived from fisher Local Ecological Knowledge (LEK, 87 interviews) showed substantial declines in shark population abundance (>65%) and distribution (>60%) between 1970-2019. Validation of contemporary spatial LEK using Baited Remote Underwater Videos (BRUVs, 50 hours of footage) highlighted the potential of LEK to provide fine-scale distribution data for shark populations in data poor regions. Analysis of BRUVs (464 hours of footage) and citizen science data (2,024 dives) over a 5-year period (2016-2020) revealed historical population declines have now been halted and suggests species abundances are stable following sanctuary implementation. However, positive correlations between prey and reef shark abundance raises uncertainty over the long-term efficacy of sanctuaries, which still permit exploitation of prey species. Interviews with fishers (n = 103) identified correlations between fisher characteristics, perceptions, and support for the Maldives shark sanctuary. Findings identified several management actions that could increase support: increasing stakeholder participation and representation (voice to capture local knowledge); mitigation of the costs associated with fisher-shark interactions and increasing transparency in management decision making. The potential severity and inequity in livelihood costs associated with shark sanctuaries was also highlighted revealing that small-scale reef fishers were disproportionally impacted compared to pelagic tuna fishers. This thesis highlights the importance of integrating human and ecological dimensions into shark conservation to tailor measures more likely to be effective in specific contexts and suggests that low support for sanctuary regulations, fisher-shark conflict and overexploitation of reef resources, could hinder long-term population recovery. Findings outline rapid, cost-effective approaches towards generating priority data to provide a basis for evidence-based management that will help define future efforts to enhance shark conservation in the context of achieving the UN Sustainable Development Goal (SDG) 14.