Multiple approaches and novel techniques to study the spatial ecology of marine vertebrates.
Pikesley, Stephen Kenneth
Thesis or dissertation
University of Exeter
Reason for embargo
I wish to place an embargo on my thesis to be made universally accessible via ORE, for a standard period of 18 months because I wish to publish papers using material that is substantially drawn from my thesis.
To mitigate potential negative impacts to marine vertebrates it is necessary to gain, and build on, knowledge and understanding of their spatial ecology. Aerial and ship based surveys, as well as satellite telemetry data, have allowed for growing insight into habitat use across a broad spectrum of migratory marine species. Furthermore, these data have often enabled characterisation of anthropogenic impacts and identified potential conservation management strategies. This thesis seeks to investigate the spatial ecology of marine vertebrates using sea turtles as a study group. Data for inter-nesting and post-nesting sea turtles are analysed, and where possible, threats investigated. The analyses presented here integrate the use of multiple spatial ecological tools, including aerial surveys, satellite tracking, remote sensing, Geographical Information Systems (GIS) and habitat modelling. Many of the analytical processes employed formulate novel methodologies, as well as build upon and develop existing techniques. For post-nesting turtles, foraging and migratory data are analysed, and observed and modelled habitat niches described. Putative threats from fisheries and climate change are investigated, and where appropriate, contextualised with data describing limits of Marine Protected Areas (MPAs). For inter-nesting turtles, at-sea distributions and coastal density patterns are explored. Vessel Monitoring System (VMS) and Automatic Identification System (AIS) data are used to elucidate shipping densities; spatial patterns of threat from fisheries, and other maritime industries are inferred. Aerial survey data are used to ascertain potential impacts to turtles on nesting beaches. Throughout this thesis spatially explicit areas are identified where concentrated conservation efforts could be applied. Furthermore, many of these analyses highlight that conservation policy must recognise the spatial extent of migratory species, and be flexible and adaptive to accommodate potential range shifts under climate change. Much of the presented analyses assimilate data from multiple sources to provide large datasets; allowing analyses to be made that would be otherwise unfeasible. Finally, this thesis demonstrates the utility of developing and applying novel analytical methodologies to these data to investigate the spatial ecology of marine vertebrates of conservation concern. As such, it is likely that many of the analytical techniques presented here could be adapted and applied to other widely dispersed marine vertebrate species to help inform global conservation planning and practice.
Pikesley, S.K., Agamboue, P.D., Bonguno, E.A., Boussamba, F., Cardiec, F., Fay, J.M., Formia, A., Godley, B.J., Laurance, W.F., Mabert, B.D.K. & others. (2013) Here today, here tomorrow: Beached timber in Gabon, a persistent threat to nesting sea turtles. Biological Conservation, 162, 127–132.
Pikesley, S.K., Broderick, A.C., Cejudo, D., Coyne, M.S., Godfrey, M.H., Godley, B.J., Lopez, P., López-Jurado, L.F., Elsy Merino, S., Varo-Cruz, N., Witt, M.J. & Hawkes, L.A. (2014) Modelling the niche for a marine vertebrate: a case study incorporating behavioural plasticity, proximate threats and climate change. Ecography, 38, 803–812.
Pikesley, S.K., Maxwell, S.M., Pendoley, K., Costa, D.P., Coyne, M.S., Formia, A., Godley, B.J., Klein, W., Makanga-Bahouna, J., Maruca, S., Ngouessono, S., Parnell, R.J., Pemo-Makaya, E. & Witt, M.J. (2013) On the front line: integrated habitat mapping for olive ridley sea turtles in the southeast Atlantic. Diversity and Distributions, 19, 1518–1530.
PhD in Biological Sciences