The first known manta ray nursery was discovered by accident


The world’s first confirmed manta ray nursery was found thanks to some good luck.

Marine scientist Joshua Stewart, was working to connect the dots between manta ray populations that live near each other at the National Oceanic and Atmospheric Administration’s Flower Garden Banks National Marine Sanctuary.

What he found instead, according to a new study published in Marine Biology, was something he had barely seen in his seven years of manta ray research: a juvenile manta ray.

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“On my very first dive, I saw a manta right away. [Researchers at Flower Garden Banks] had already told me that the rays there were small, so I wasn’t shocked,” Stewart said in an interview. 

But when he went to take a picture of the spot pattern that essentially serves as a fingerprint on the ray’s underside, he saw that the ray had a really small set of male genitals, meaning that he was a juvenile. 

The team at Flower Garden Banks told him that kind of sighting was also common, which prompted him to ask for their  photo archive.

Using the catalogue with 25 years of diving pictures, Stewart and staff were able to analyze the spot patterns on the bellies of countless rays to identify individuals and calculated that 95 percent of the manta rays that visit the sanctuary were actually young.  

Juvenile manta ray at Flower Garden Banks National Marine Sanctuary

Juvenile manta ray at Flower Garden Banks National Marine Sanctuary

Image: G.P. Schmahl / FGBNMS

When scientists study rays, they look for large groups of the animals, but the researchers have historically been unable to find large groups of juveniles, leaving a big hole in the research. Stewart’s discovery of the manta ray nursery around the research site fills that hole.

For aquatic life, nurseries serve as a sort of unsupervised daycare where groups of young fish can grow without the fear of being hunted by larger prey. 

Now that researchers know that is Flower Garden Banks is a nursery, they will be able to look for similarly situated spaces around the world and hopefully find more. 

“We know that other nurseries are out there. Flower Garden Banks is just the only one we’ve been able to confirm,” Stewart said. 

Juvenile male manta at Flower Garden Banks National Marine Sanctuary

Juvenile male manta at Flower Garden Banks National Marine Sanctuary

Image: G.P. Schmahl / FGBNMS

There have been sightings of little groups of juveniles all over the globe, but it will take years to confirm whether those groups lead to nurseries. 

In the future, Stewart and the other researchers out of the Flower Garden Banks National Marine Sanctuary hope to start tagging the juveniles to track their movements.

This will help them determine what the juveniles like about the banks so much. 

Stewart’s guess? Safety. 

With other marine life nurseries, access to food and safety from predators are two cornerstones that draw the youth to these hubs, he explained. The only way to know is to keep observing. 

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