Horizontal and vertical movements of longfin makos (Isurus paucus) tracked with satellitelinked tags in the Northwestern Atlantic Ocean

Abstract

The longfin mako (Isurus paucus) is a poorly studied oceanic shark taken in fisheries throughout its worldwide range in temperate and tropical waters. Satellite-linked tags were deployed to investigate the movements of 2 mature males, one tagged in the northeastern Gulf of Mexico (GOM) and the other off northern Cuba. Horizontal tracks estimated by using likelihood methods were similar for these sharks; comparable movements were documented from the GOM, through the Straits of Florida and the Bahamas, and into the open Atlantic Ocean where they converged on the Mid-Atlantic Bight. Depth and temperature ranges were 0–1767 m and 4.0–28.8°C. A diel pattern of vertical movement was evident for both individuals, along with regular forays from cold daytime depths to warmer near-surface waters, possibly as an adaptation for thermoregulation. The vertical movements of longfin makos allow them to exploit vertically migrating prey but these movements increase their vulnerability to pelagic longlining. The horizontal movements of these sharks reveal the limited benefit of areas currently closed to pelagic longlining off the southeastern United States and also indicate the connectivity of U.S., Cuban, Mexican, and Bahamian waters for this species. Because of the vulnerability of longfin makos to overexploitation, improved biological information is needed for accurate stock assessments and appropriate management and conservation measures.