Summit County Citizens Voice

A giant manta swimming in the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico. Image courtesy NOAA.

New study to help inform conservation policy

By Summit Voice

SUMMIT COUNTY — While images of manta rays are ubiquitous on brochures and websites for popular seaside tourist destinations, very little is known about where the ocean giants live and what they need to survive.

But that’s starting to change, thanks to an international study that used satellite tracking technology to study manta rays off the coast of Mexico’s Yucatan Peninsula over a 13-day period. The tracking devices were attached to the backs of six individuals —four females, one male, and one 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.”

Other efforts to track manta rays are also under way, for example at the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico, where resource managers have developed a photo catalogue of individual mantas to help figure out how much time they spend at the sanctuary and where else they might visit.

Mantas are the world’s largest rays, growing as large as 25 feet in width. They are listed as vulnerable on the International Union for Conservation of Nature’s Red List due to increasing threats from fishing and accidental capture.

Anecdotal evidence suggests manta rays are declining in the Caribbean and in other tropical regions of the world’s oceans, in part because they are captured for shark bait. They are also killed in order to harvest their gill rakers (small, finger-like structures that filter out the ray’s minute zooplankton prey) used in the traditional Chinese medicinal trade.

The groundbreaking study should help marine biologists learn more about habitat needs, the first step in designing a conservation strategy.

“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.”

Like baleen whales and whale sharks, manta rays are filter feeders that swim through clouds of plankton with mouths agape.

The research team also found that the manta rays spent nearly all their time within Mexico’s territorial waters (within 200 miles of the coastline), but only 11.5 percent of the locations gathered from the tagged rays occurred within marine protected areas. And the majority of ray locations were recorded in major shipping routes in the region, where manta rays could be vulnerable 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.

In spite of its malevolent, bat-like appearance, the manta ray—sometimes referred to as the “devilfish”—is harmless to humans and lacks the stinger of the better-known stingray.

The manta ray possesses the highest brain to body ratio of all sharks and rays and gives birth to live young, usually one or two “pups” every one or two years.

The study was published today in the online journal PLoS One. The authors include: Rachel T. Graham of the Wildlife Conservation Society and the University of Exeter; Matthew J. Witt of the University of Exeter; Dan W. Castellanos of the Wildlife Conservation Society; Francisco Remolina of the National Commission of Protected Areas, Cancun, Mexico; Sara Maxwell of the Marine Conservation Institute and the University of California-Santa Cruz; Brenden J. Godley of the University of Exeter; and Lucy A. Hawkes of Bangor University, Bangor, United Kingdom.

Filed under: biodiversity, Environment, Marine biology Tagged: | biodiversity, Environment, Flower Garden Banks National Marine Sanctuary, Gulf of Mexico, manta rays, ocean conservation, Wildlife Conservation Society