Scripps Institution of Oceanography, University of San Diego, California
Giant Manta (Manta birostris) can live more than 40 years and can measure up to 7 meters from wingtip to wingtip. It spends most of its life in remote ocean environments such as seamounts and oceanic islands, devoting its time to looking for food, small floating organisms known as plankton.
Traditionally it was thought that the giant manta made epic migrations, however, according to a new study, it seems that this is a very local creature. A team of researchers led by the Scripps Institution of Oceanography at the University of San Diego, California, studied the giant manta by satellite tracking to clarify the mysteries of the life of these giants. Their findings, published in the journal Biological Conservation, contain large implications for the conservation of endangered species.
To better understand the travels of the giant Manta, the researchers placed their satellite tracking equipment and took muscle samples from the animals at four sites in the Pacific Ocean, separated by more than 13,000 kilometers, to find out whether small aggregations of giant Manta were really connected forming a large network of sub-populations.
Using satellite data, which includes about six months of information on the movements of the giant manta, along with genetics and stable isotopes obtained from the muscle of these organisms, the researchers found that the giant Manta remained near the site where they were found at baseline, and that they are subpopulations with very different genetic information, meaning very little connectivity between regions.
“These animals are showing an incredible level of residence, when compared with what we expected regarding their migrations,” said doctoral candidate in science at Scripps, Joshua Stewart, a researcher at Scripps in the Gulf of California Marine Program, and main research author. “Sometimes the mantas make long journeys. However, the rule is to stay close. This means that any population of giant manta is highly susceptible to fishing and other impacts caused by man, but also because they are local, the populations are easier to protect.”
The populations of giant manta and other similar species are diminishing increasingly on a global level, due to the consumption of its gills, used in traditional Chinese medicine, and due to bycatch. Previously, science assumed that the giant manta was an animal with migratory habits, like many other large sized animals, such as sharks, tuna, and whales. But, “We found that patterns of residence of the manta remain intact through studies on a multiyear and generational scale, thanks to genetic and isotope studies,” says Josh Stewart, who is also a researcher at the British non-profit organization, Manta Trust. According to the authors, this study shows that the giant manta can be protected effectively with management strategies at the local level, which are not normally considered for migratory species.
“The research we have done has shown that perhaps the best management strategies for the giant manta could be at local or national levels,” said study co-author Calvin Beale of the Misool Manta Project. The population of giant manta in Indonesia appears to reside exclusively in the territorial waters of the country, where protection measures are in place for manta rays, plus much of the distribution area of the giant manta is protected there.
“If more countries follow suit and protect their populations of manta rays, the future of the species can be much better than today,” said Calvin Beale. In another recent study published in the journal, Zoology, Stewart and his team analyzed the diving behavior 6 Mantas in the Revillagigedo Archipelago, Mexico. They found seasonal changes in behavior due the availability of food.
“Mexico has a great opportunity to protect the giant mantas and generate large economic benefits from this protection,” said Dr. Octavio Aburto-Oropeza, study co-author and professor-researcher at the Scripps Institute of Oceanography. “The Revillagigedo Archipelago and the community of Yelapa, Jalisco in Banderas Bay, could be Mexican areas that demonstrate the tremendous potential for ecotourism, by taking care of these great animals,” he concluded.
Note: The foundations, associations and groups, New England Aquarium’s Marine Conservation Action Fund, PADI Foundation, Save Our Seas Foundation, Misool Baseftin, Carl F. Bucherer, Conservation International, SEA Aquarium Singapore, The Punta Mita Foundation, National Geographic Society/Waitt Grants Program, and private donors have supported this study. Josh Stewart also is supported by: National Science Foundation Graduate Research Fellowship, a Switzer Environmental Fellowship, and Nancy Foster Scholarship through the NOAA Office of National Marine Sanctuaries.
About Scripps Institution of Oceanography
Scripps Institution of Oceanography at the University of California, San Diego is one of the oldest, largest and most important world centers of scientific research and education in the world. It is now the second century of discovery, and the scientific view of this institution has grown and included biological, physical, chemical, geological, geophysical and atmospheric studies of the earth as a system. Hundreds of research programs are developed covering a wide variety of branches of science on every continent and ocean. Scripps operates oceanographic ships with unique capabilities that are recognized worldwide. Equipped with state-of-the-art ocean exploration equipment, these vessels are mobile laboratories and observatories that help students and researchers from institutions throughout the world. The aquarium, Birch Aquarium at Scripps, serves as an interpretive center of the institution, and shows research from the institution and a variety of marine life through exhibits that receive more than 430,000 visitors per year. To learn more visit: www.scripps.ucsd.edu and follow us on Facebook | Twitter | Instagram.
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