Use of Mesoscale Eddies by Pelagic Sharks

Peter Gaube, Applied Ocean Physics & Engineering
Simon Thorrold, Biology

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2014 OLI Funded Project

Abstract

Mesoscale eddies, large swirling bodies of water with horizontal scale on the order of 100 km, are a common feature of the World Ocean, covering nearly 30% of the ocean surface at anytime.  Eddies influence primary production in the ocean in numerous ways, including generating upwelling and downwelling and transporting ecosystems over large distances.  How megafauna, such as sharks and other pelagic fishes, interact with eddies still remains largely a mystery.  The proposed project will develop our understanding of how eddies are used by megafauna through the analysis of sharks’ trajectories recorded by high-precision SPOT (Smart Position or Temperature Transmitting) satellite tags with contemporaneous observations of the location and movement of mesoscale eddies identified and tracked in satellite-derived maps of sea surface height.  Our preliminary analysis suggests that white sharks in the North Atlantic are significantly more likely to occupy the interiors of clockwise rotating anticyclonic eddies versus counterclockwise rotating cyclonic eddies.  The first phase of this project will expand this analysis to other white sharks in the North Atlantic and Southwestern Indian Oceans to investigate if the observed preference for anticyclones is ubiquitous across different shark species and various geographic regions.