First insights into the movements and vertical habitat use of blue marlin (Makaira nigricans) in the eastern North Atlantic

Abstract

Background

The blue marlin (Makaira nigricans) is a vulnerable migratory fish inhabiting tropical and subtropical pelagic waters of the Atlantic, Pacific and Indian Oceans. The biology and spatial ecology of the species in the eastern North Atlantic is poorly understood, despite being exploited in the region by recreational and commercial fisheries. Here, we present results of the first study to use pop-up satellite archival tags to track blue marlin off Madeira, Portugal (n = 3) and obtain insights into the movements and habitat use of the species within the eastern North Atlantic.

Results

Blue marlin were tracked for 24 to 83 days, moving from Madeira to pelagic waters off the Canary Islands, Cape Verde Islands, as well as along the continental shelf brake of Europe and Africa. Blue marlin spent 71% of their time in the upper 5 m and 89% in the upper 50 m, though all individuals dived to depths over 200 m (maximum: 336 m). Temperature at depth ranged from 12 to 28.6 °C, but the greatest proportion of time was spent in waters between 20 and 26 °C. Detailed depth and temperature time-series data were obtained from a tag recovered eight years later. These data show clear diel differences in depth use, involving consistent use of the surface at night and deeper dive activity during the day, predominately to depths greater than 50 m.

Conclusions

The highly migratory patterns of this vulnerable species in the eastern North Atlantic highlights the need for both local and international conservation measures. Depth-use patterns, particularly the high usage of the upper 5 m of the water column, make them susceptible to surface longline fisheries.