For the first time ever, a nursery for endangered ray pups and adolescents has been discovered – giving researchers hope to learn more about these rare gentle giants.
Meet the glorious giant manta ray. Mobula birostris is the world’s largest ray with a wingspan of up to 29 feet – a 72-passenger school bus is not much longer than that. These gentle giants are filter feeders who live off of large quantities of zooplankton. Slow-growing and migratory, they comprise small, highly fragmented populations that are sparsely scattered across the planet's oceans.
Unfortunately, thanks to commercial fishing, NOAA Fisheries listed the species as threatened under the Endangered Species Act just this year. "Given their life history traits, particularly their low reproductive output," NOAA explains, "giant manta ray populations are inherently vulnerable to depletions, with low likelihood of recovery." NOAA concludes that research is lacking and more of it needs to take place.
Which is why a recent discovery by a graduate student at the University of California San Diego's Scripps Institution of Oceanography is making waves.
The student, Josh Stewart, was on his first dive at the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico, about 70 miles south of Houston, when he identified what has now become the first recognized nursery ground for giant oceanic manta rays. NPR describes it as "a sort of safe playground for the growing gentle-giants, from newborns to adolescents."
"I was there trying to get a genetic sample from a full grown manta, and that's when I saw it. It was a juvenile male manta, which is a very rare," Stewart told NPR. Prior to that, Stewart had only seen two or three juvenile manta rays in his seven years of studying them.
"That was super cool," Stewart says he told the other researchers who've worked at the sanctuary for years. "We see them all the time," they said. "And that's when I knew that this was a really special, unique place," Steward recalled.
The scientists who had been researching the area didn't realize the place was rampant with youths, instead thinking that the smaller ones were another species.
A study about the discovery has been published in Marine Biology. The authors note, "While studies of oceanic mantas have increased substantially in the past decade, major knowledge gaps remain in their basic biology, ecology and life history. The juvenile stage in particular is virtually unstudied, as juvenile oceanic mantas are rarely observed in the wild and are known primarily from ﬁsheries and captive individuals"
Stewart's remarkable discovery will provide loads of new and valuable information, and is expected to serve as a major nudge forward in the scientific understanding of the species.
"The juvenile life stage for oceanic mantas has been a bit of a black box for us, since we're so rarely able to observe them," says Stewart. "We don't know much about their movements, their feeding behavior and how that compares to the adults. Now we have a pool of juveniles that we can study."
Experts say that the new research will help identify and protect other other critical habitats, which can't come a minute too soon considering the threats that the rays are facing. As study co-author Michelle Johnston says, "Threatened species need a safe space to grow up and thrive and live."
See footage and learn more in the video below.