Satellite Tracking of Manta Rays Highlights Challenges to Their Conservation

Rachel T Graham,Howard Browman,Sara Maxwell,Francisco Remolina,Matthew J Witt,Brendan J Godley,Lucy A Hawkes,Dan W Castellanos

doi:10.1371/journal.pone.0036834

Abstract

We describe the real-time movements of the last of the marine mega-vertebrate taxa to be satellite tracked – the giant manta ray (or devil fish, Manta birostris), the world's largest ray at over 6 m disc width. Almost nothing is known about manta ray movements and their environmental preferences, making them one of the least understood of the marine mega-vertebrates. Red listed by the International Union for the Conservation of Nature as ‘Vulnerable’ to extinction, manta rays are known to be subject to direct and incidental capture and some populations are declining. Satellite-tracked manta rays associated with seasonal upwelling events and thermal fronts off the Yucatan peninsula, Mexico, and made short-range shuttling movements, foraging along and between them. The majority of locations were received from waters shallower than 50 m deep, representing thermally dynamic and productive waters. Manta rays remained in the Mexican Exclusive Economic Zone for the duration of tracking but only 12% of tracking locations were received from within Marine Protected Areas (MPAs). Our results on the spatio-temporal distribution of these enigmatic rays highlight opportunities and challenges to management efforts.

Highlights

Satellite tracking has yielded key information about the life history of marine vertebrates, many of which engage in long migrations [1] and make deep dives [2], beyond the temporal and logistical abilities of researchers to follow them
Manta rays were found to encompass a second species Manta alfredi that ranges throughout the Central Eastern Atlantic and Indo-Pacific and possibly a third species constrained to the Gulf of Mexico and the Caribbean [8]
Most manta ray locations occurred further than 20 km offshore (92% of all locations) and only 11.5% locations occurred within Marine Protected Areas (MPAs) (Fig. 2 a)

Summary

Introduction

Satellite tracking has yielded key information about the life history of marine vertebrates, many of which engage in long migrations (travelling thousands of kilometres) [1] and make deep dives [2], beyond the temporal and logistical abilities of researchers to follow them. Manta rays (or devil fish, Manta birostris) are the world’s largest batoid fish (reaching a measured disc width of 7.1 m), with slow growth and low fecundity, birthing only one or two live ‘pups’ every one to two years following a gestation period of 12 months [7]. They are listed by the International Union for Conservation of Nature (IUCN) as ‘‘Vulnerable’’ to extinction [7] and included on Appendix I and II of the Convention on Migratory Species of Wild Animals. The manta rays may be the least understood of the marine mega-vertebrate groups, and one of the last to be satellite tracked

Methods

Results

Conclusion