World Manta Day: Finding Flatsharks

Despite being the world’s largest rays, spanning up to 29 feet from wingtip to wingtip, the whereabouts of giant manta rays in the U.S. has largely remained a mystery to researchers — until recently.

A new study, published in the journal Scientific Reports, and co-authored by Stephen Kajiura, Ph.D., a professor in the Charles E. Schmidt College of Science, has narrowed down when and where to expect manta rays, which are part of the elasmobranch group that includes sharks, skates and other rays. These gentle giants were listed on the U.S. Endangered Species Act in 2018, “so it is very important to learn as much as we can about their life history and behavior in order to develop effective management plans,” Kajiura said.

Researchers from across the country combined their data of manta ray sightings, as well as sighting information from the public, to map out their distribution. Since Kajiura regularly flies planes for his shark research and records when he spots mantas, he had data to contribute. “By pulling together data from various researchers, we were able to create a much larger study than any single research organization could achieve on its own,” he said.

The study also created predictive models of where and when to find the mantas, by correlating environmental information, such as water temperature. “This is important because as ocean water temperatures continue to rise, this might affect the distribution and movements of mantas in the future,” Kajiura said.

According to the research, the manta rays are most often found close to the shore and where deep cold water rises to the surface. Off the northeastern coast of Florida, they are found in the highest numbers in April. As temperatures warm, they are found in higher numbers north of Cape Hatteras, N.C. from June to October, and then south of Savannah, Ga., from November to March as temperatures cool. In the Gulf of Mexico, the highest nearshore occurrence was predicted around the Mississippi River delta from April to June and again from October to November.

South Florida has its own population of young manta rays that can be found right up against the beach. They are often found with trailing fisher gear, Kajiura said. “Learning what we can about their distribution allows us to be better informed and minimize any negative impacts on this ecologically important and charismatic species.”