Researchers at the Marine Megafauna Foundation (MMF) have discovered a population of sicklefin devil rays (Mobula tarapacana) off the Atlantic coast of the US, according to a new study. Led by MMF researcher Jessica Pate, this marks the first recording of these huge, elusive rays in the eastern coast of the United States. Listed as Endangered by the International Union for Conservation of Nature (IUCN), this ray is easily distinguished from other devil rays by their olive-green to brown coloration. Their unique coloration extends to their gill plates, which are black-and-white and sometimes referred to as ‘flower gills.’ As one of the most commonly traded mobulid rays after the Oceanic Manta and Spinetail Devil Ray, their gill plates fetch the second highest price after mantas. As a species with a wide distribution in the tropics as well as in warm temperate seas, they are also the deepest divers among the mobulids, reaching depths of over 6,560 feet (2,000 meters) where temperatures plummet to freezing conditions.
In 2018, US Country Manager Pate received a photo of a sicklefin devil ray taken by Florida scuba diver Jeff Joel: ““The original impetus for this study was a citizen science report sent to the Florida Manta Project, which led to sightings in other databases. One sighting even involved a video of a devil ray accidentally swimming into a commercial saturation diver’s airline in the darkness! People often don’t know that these rays exist – they’ve sometimes been confused with manta rays, which are even more gigantic. This study shows how non-scientists often make really important observations, and contribute to the conservation of endangered species.” In response, she established a collaboration between MMF, NOAA Fisheries, and Normandeau Associates Inc., compiling sightings from scuba divers, social media platforms, aerial surveys, and reports from fisheries observers. There were 180 documented sightings and 361 individual sicklefin devil rays, gathered between 1996 and 2022 in the waters off the US east coast and Gulf of Mexico.
“Normandeau is delighted that they could contribute to this body of knowledge. This is an example of how important it is to freely share data. In this case, we utilized data collected to assist in the responsible siting of offshore wind projects by the Bureau of Ocean Energy Management and the New York State Energy Research and Development Authority, all of which help to further our understanding of the species that inhabit our oceans,” Normandeau Associates Inc. representative Julia Wilmott said in a press release.
It was not common practice prior to mid-2019 for US fisheries observers to classify accidental catches of rays according to their actual species. To make informed management decisions, researchers and conservationists need an accurate representation of species in future bycatch data. This new study sheds light on the potential overlap between sicklefin devil rays and US Atlantic fisheries, highlighting areas where the species may be captured accidentally by industrial longlines. “Little is known about sicklefin devil rays in the United States. This study highlights how incidental observations and observer data can provide vital knowledge on rare, vulnerable, and difficult to study species,” says Pate. “We hope this encourages other researchers and managers to examine regional databases for information on other data-poor species.”