The basking shark Cetorhinus maximus
: movement, behaviour and connectivity in the Northeast Atlantic

  • Emmett Johnston

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

This thesis addressed several key questions in the basking shark (Cetorhinus maximus) regarding surfacing behaviour and thermal ecology as well as, connectivity between recognised coastal sites for seasonal aggregation. This study focused on a seasonal ‘hotspot’ for basking sharks at Malin Head, Ireland. In Chapter 2 we used data collected by time depth recorders deployed on basking sharks (N=13; total 466.5 hours) to develop a two state (diving - surfacing) Semi-Markov model that predicts the frequency and duration of basking shark surfacing events using solar radiation or wind speed alone. This approach will address availability bias in population census data. In Chapter 3 we explored the physiology and evolutionary history of basking sharks through the comparative study of breaching events captured using animal borne triaxial accelerometer, depth and video data (CATSCAM) with video data remotely captured from the shore (N=20). In Chapter 4 we used Pop-off archival transmitters with Fastloc GPS (Wildlife Computers) (n=4) to consider how patterns of depth utilisation during autumnal dispersal from hotspots, might shape the basking shark’s realised thermal environment. Sharks concurrently dispersed into coastal mixed and stratified, offshore tropical and subtropical habitats, where ambient water temperatures experienced reflected habitat occupied. In Chapter 5 we used a combination of mark-recapture (coloured and numbered visual tags; n=465) and satellite tracking (Smart Position and Temperature tags, SPOT; n=10) methods to investigate the interconnectivity of basking shark surface hotspots across the North Atlantic. Re-sightings and satellite tracks showed connectivity within given years between all known surface hotspots in the ROI and UK as well as confirming inter-annual connectivity between Irish, UK and US hotspots. The final chapter draws together the key findings from each of the experimental chapters and reflects on their relevance for species management, conservation and future studies.
Date of AwardJul 2021
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsNational Parks and Wildlife Service Ireland
SupervisorJonathan Houghton (Supervisor), Patrick Collins (Supervisor) & Paul Mensink (Supervisor)

Keywords

  • Basking shark
  • conservation
  • movement and connectivity
  • behaviour
  • north east Atlantic

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