| dc.description.abstract | With marked declines in populations globally, understanding the spatial ecology of elasmobranchs is critical for effective conservation and management. Terrestrial and aerial behavioural ecology has developed approaches which position target species within the context of their wider environment, providing impactful insight into species and community ecology. However, marine studies often fall short of integrating these influences, in large part due to lags in the development of theoretical and methodological approaches to tackle the complex behaviours exhibited by marine vertebrates. In this thesis, I explore innovative methodologies to enhance our understanding of marine vertebrate spatial ecology, integrating novel theoretical frameworks, analytical techniques, and methodological approaches, with applications in Bimini, The Bahamas, and Cornwall, UK.
Central to this thesis is the development of the Seascape of Ecological Energy (SEE-scapes) framework, synthesising decades of marine biology and behavioural ecology research by considering both abiotic and biotic factors in understanding behavioural patterns of marine vertebrates. SEE-scapes provides solutions for sampling and modelling eco-evolutionary drivers of behaviour across dynamic seascapes and aims to guide marine scientists in grounding their research in behavioural ecology principles.
Building on this theoretical foundation, I first investigate juvenile shark behaviour in a semi-pristine lagoon in Bimini. The work conducted in Bimini takes advantage of two years of juvenile lemon shark (Negaprion brevirostris) positional data from passive acoustic telemetry, and decades of investigation into the faunal biodiversity and distribution, and composition of habitat, across Bimini. Collaborations with researchers from the Bimini Biological Field Station Foundation (BBFSF) provided data from baited remote underwater video surveys (BRUVS) on the distribution of teleost and invertebrates, including key diet families of lemon sharks (Gerridae sp., Haemulidae sp., Lutjanidae sp., Scaridae sp.); positional data on large-bodied elasmobranchs (Negaprion brevirostris, Carcharhinus limbatus), the top predators of juvenile lemon sharks in The Bahamas; and remote sensed data describing the aquatic and terrestrial habitat features of Bimini. I used these time-matched data on various ecological nodes within the SEE-scape of the juvenile lemons to explore the drivers of juvenile spatial behaviour, identifying implications for conservation and insight into the relevant eco-evolutionary concerns for juvenile elasmobranchs at a vulnerable life stage. Through a detailed analysis of habitat selection, this thesis reveals how young sharks interact with their physical environment, particularly emphasizing the importance of features which imbue structure or refuge into the coastal environment, e.g. mangroves. The study follows nearly two decades of marked coastal development along the interior coastline of the lagoon and provides direct comparison to a study pre-dating the onset of development. And in the context of historic movement ecology of juvenile sharks, I discuss divergences in juvenile shark behaviour following coastal development. These findings have significant implications for conservation strategies and coastal management, while also providing a workflow for integrating passive acoustic telemetry, a common biologging tool in aquatic environments, into habitat selection frameworks.
Next, to explore the hierarchical drivers of juvenile shark behaviour in a risk versus resource context, I tested three hypotheses using Bayesian structural equation model (BSEM) with path analysis. The results indicate that juvenile sharks prioritise predation risk over prey availability, with moderate evidence suggesting that habitat and human activity information influences juvenile shark behaviour indirectly, only insofar as it aids in predicting resource availability and risk. These findings highlight the necessity of understanding dynamic ecological relationships to develop effective management strategies for juvenile shark populations. This study is the first of its kind, at time of writing, to take such an approach: applying BSEM and path analysis to understand and predict distributions of juvenile sharks based on the hypothesis with the most empirical support.
Finally, in exploring solutions for quantifying the cryptic behaviour of marine vertebrates, I evaluate the efficacy of a novel environmental DNA (eDNA) sampling method, the Metaprobe 2.0, in detecting elasmobranch and teleost species in pelagic waters of Cornwall, UK. Given the global biodiversity crisis, developing accessible methods to fill knowledge gaps and provide critical data on the spatial behaviour of elasmobranchs is crucial. Compared to standard methods, Metaprobes demonstrate good performance in biodiversity monitoring, and offer a cost-effective and efficient alternative for studies of spatial ecology and conservation efforts in remote marine environments.
Overall, this thesis advances methodologies for studying elasmobranch behaviour, offering frameworks and workflows that integrate ecological drivers across multiple scales. These contributions aim to enhance conservation and management efforts, providing a deeper understanding of marine biodiversity and behaviour in the face of environmental change. | en_GB |
