May 11th, 2012 by James Ayre
The first study on manta rays to use satellite telemetry has just been released. The study tracks the long journeys of the giant, up-to-25-feet-wide manta ray.
The manta ray, which is currently listed as ‘Vulnerable’ by the International Union for Conservation of Nature(IUCN), is increasingly threatened by fishing and accidental capture.
“Almost nothing is known about the movements and ecological needs of the manta ray, one of the ocean’s largest and least-known species,” said Dr. Rachel Graham, lead author on the study and director of WCS’s Gulf and Caribbean Sharks and Rays Program. “Our real-time data illuminate the previously unseen world of this mythic fish and will help to shape management and conservation strategies for this species.”
The research was done by attaching satellite trackers to manta rays off the coast of the Yucatan Peninsula. Specifically, onto six individuals, of which four are adult females, one is an adult male, and one is juvenile.
“The satellite tag data revealed that some of the rays traveled more than 1,100 kilometers during the study period,” said Dr. Matthew Witt of the University of Exeter’s Environment and Sustainability Institute. “The rays spent most of their time traversing coastal areas plentiful in zooplankton and fish eggs from spawning events.”
The research found that while they spent almost all their time in the coastal waters, they were only in marine-protected areas 11.5 percent of the time. The majority of their time was spent in areas used as major shipping routes, leaving them open to ship strikes.
“Studies such as this one are critical in developing effective management of manta rays, which appear to be declining worldwide,” said Dr. Howard Rosenbaum, Director of WCS’s Ocean Giant Program.
Regardless of how they look, they are harmless to humans. They also possess the highest brain-to-body ratio of all sharks and rays. And they give birth to live young, at a slow pace, one or two to a litter, every two years or so.
Their numbers have been decreasing around the world, largely because of being caught for shark bait and demand for their filters, used in traditional Chinese medicine.
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