Horizontal and vertical movements and habitat use of the common thresher shark Alopias vulpinus in the western North Atlantic

Abstract

In the western North Atlantic (WNA), the common thresher shark Alopias vulpinus is captured by several fisheries, but its population status has not formally been assessed, and its ecology and population structure are poorly understood. A total of 61 pop-up satellite archival transmitting tags were deployed to study the species’ horizontal and vertical movement patterns and habitat use in the WNA and to inform the formulation of fishery management policy. Tracking data from 48 individuals ranging from 122 to 259 cm fork length revealed widespread horizontal movements throughout the WNA between northeastern Florida north and east to the Grand Banks of Newfoundland. Seasonal migrations across continental shelf and off-shelf habitats were identified in both juveniles and adults. Tagged common thresher sharks inhabited a wide temperature range in the WNA (-0.5 to 25.6°C), but spent ~90% of their time in waters between 14 and 20°C. Depth distribution ranged from the surface to 1822 m, with ~87% of time spent at depths shallower than 50 m. Deeper depths were achieved during the winter, spring, and fall than during the summer. These results will assist with the identification of important geographic locations of occurrence for both juvenile and adult common thresher sharks, help forecast the effects of environmental change on the species’ distribution, and inform the relevant spatial scales for fishery management policies and stock assessment.

Full Text

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