Conference Contribution Details
Mandatory Fields
Doyle, T.K., Bennison, A., Jessopp, M.J., Haberlin, D., Harman, L.
5th Biologging Symposium
Analysis of the timing of data acquisition provides insights on blue shark surfacing behaviour
Strasbourg, France
Poster Presentation
Optional Fields
The Argos satellite system has been used extensively for tracking migrations of marine animals. We present an alternative analysis of a satellite tracking dataset to investigate the behaviour of blue sharks (Prionace glauca) using ‘timing of data acquisition’. We deployed three SPOT tags (Wildlife Computers) on blue sharks in Irish waters during 2012-2013. The sharks were tracked for 73-211 days and all made southern migrations to warmer tropical waters. Due to the position of the tag (dorsal fin mount), data acquisitions (or ‘messages’) were only received by the Argos satellite system when the sharks’ dorsal fins were knifing through the surface and when satellites were overhead. Despite the fact that sharks have no known physiological need to surface, a total of 1317 surfacing events were recorded. Mixed effect models (controlling for bias in satellite coverage), showed an increasing trend in surfacing events around dawn, peaking approximately 1 hour after sunrise (R2=0.443, Chi24=38.435, p=<0.001). It is uncertain why the most abundant large oceanic predator surfaces more at this time, but is likely to be linked with foraging. The application of this method to larger datasets and other species is likely to increase our understanding of the ecology of wide-ranging marine predators.