Scientists Discover More Than 22,000 Endangered Manta Rays off Coast of Ecuador

An oceanic manta ray.

An oceanic manta ray. Michel Guerrero / Proyecto Mantas Ecuador FMME

Scientists have identified a population of endangered oceanic manta rays off the coast of Ecuador that is 10 times larger than any other known population. The discovery offers hope for the future of the species, experts say.

“This is a rare story of ocean optimism,” Joshua Stewart, an ecologist at Oregon State University’s Marine Mammal Institute and coauthor of the research, said in a statement. “In other regions, we typically have population estimates of 1,000 to 2,000 animals, which makes this species very vulnerable. In this area, we’ve estimated that the population is more than 22,000 mantas, which is unprecedented.”

In the late 1990s, researchers at Proyecto Mantas Ecuador found that at the end of each summer, oceanic manta rays gather near Ecuador’s Isla de la Plata, a popular diving spot. From 2005 to 2018, scientists collected photos of manta rays, including many taken by recreational divers, identifying individual mantas by the unique spot patterns on their bellies. Researchers counted more than 2,800 manta rays, suggesting a total population of more than 22,000. The findings were published in the journal Marine Ecology Progress Series.

Off the coasts of Ecuador and Peru, a process known as upwelling brings cold, nutrient-rich waters to the ocean surface, helping to nourish a bounty of marine life. “It seems that this productive upwelling region is able to support huge populations of even very large animals,” Stewart said. With wingspans that can reach more than 20 feet, oceanic mantas are the largest species of ray on Earth.

In 2019, oceanic manta rays were listed as endangered by the International Union for the Conservation of Nature, owing largely to the threat from commercial fishing. Ecuador outlawed the capture of manta rays in fisheries in 2010, and Peru did the same in 2016, but the creatures are still prone to getting caught in fishing equipment, researchers said. Of the 2,800 mantas identified in the study, 71 were entangled in fishing lines, nets, or hooks, while another 277 bore injuries or scars that were likely inflicted by fishing equipment.


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