When scientists at the University of California in San Diego noticed a large number of baby manta ray sightings at Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico, they never would have dreamt that they had actually stumbled upon the first-known manta ray nursery in the world.
These gentle giants of the ocean are known to seek out and gather in areas far from the coast, so they’re rarely seen this close to shore. Meanwhile, spotting a baby manta ray is even more unusual, considering that they’re notoriously elusive even in big manta ray groups.
So, imagine Joshua Stewart’s surprise, the lead author of a study detailing the new discovery, when he locked eyes on a baby manta ray at Flower Garden Banks back in 2016.
“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,” said Stewart, who is a marine biology PhD candidate at the university’s Scripps Institution of Oceanography and the executive director of the Manta Trust, a global manta conservation program.
According to the university, the researcher has been studying manta rays since 2011 and has come across hundreds of adult individuals in the wild. But the juveniles he found at Flower Garden Banks were one of his biggest discoveries.
And, as is the case of most great discoveries, this one also happened by accident.
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It all began with one sighting of a baby manta ray, which turned into several sightings, and the strangeness of these encounters prompted Stewart to investigate whether baby manta rays are a habitual occurrence at Flower Garden Banks.
Managed by the National Oceanic and Atmospheric Administration, the area is “a pristine sanctuary” located nearly 100 miles off the Texas coast. By combing through 25 years’ worth of dive logs found at the marine sanctuary, Stewart uncovered that 95 percent of the manta rays coming to Flower Garden Banks are juveniles.
While the adults of the species have a wingspan of up to 23 feet (seven meters), these juvenile manta rays were found to measure around 7.38 feet (2.25 meters) in wingspan.
The marine biologist also checked observational footage to look for the distinctive spot patterns displayed by manta rays, which serve as “fingerprints” to help scientists identify these creatures.
The photo IDs established that the baby manta ray population gathered at Flower Garden Banks is comprised of both oceanic manta rays (Mobula birostris) “and a proposed third manta species (Mobula cf. birostris),” shows Stewart’s study, published last week in the journal Marine Biology.
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His findings reveal that the sanctuary is an “important habitat” for juvenile manta rays and confirm Flower Garden Banks as the world’s first-ever discovered manta ray nursery.
“Nowhere else in the world has a manta ray nursery area been recognized — which heightens the importance of the sanctuary for these pelagic species,” said George Schmahl, the sanctuary’s superintendent.
The researchers believe that what has attracted these baby manta rays to the welcoming waters of the marine sanctuary are the healthy coral reefs that still exist here. Their guess is that the juveniles come here to “recover body temperature” in the shallow waters of Flower Garden Banks after venturing out into deeper, colder sea.
In a news release by the university, Stewart commented on the importance of this find.
“Identifying this area as a nursery highlights its importance for conservation and management, but it also gives us the opportunity to focus on the juveniles and learn about them. This discovery is a major advancement in our understanding of the species and the importance of different habitats throughout their lives.”