By Madeleine Pierce, Marine Megafauna Foundation
A new study led by Jessica Pate of the Marine Megafauna Foundation (MMF), has shown that the sicklefin devil ray (Mobula tarapacana) is present off the US Atlantic coast. Listed as Endangered by the IUCN, the new study marks the first time that the huge, elusive ray has been documented in the eastern US.
The study was initiated when Pate, an MMF scientist and US Country Manager, received a photograph of a sicklefin devil ray from a Florida scuba diver in 2018. A subsequent collaboration between MMF, NOAA Fisheries, and environmental consultant group, Normandeau Associates Inc, documented 361 individual sicklefin devil rays across 180 sightings off the US east coast and Gulf of Mexico between 1996 and 2022.
Sicklefin devil rays – also known as Chilean devil rays – are a large and wide-ranging species, reaching up to 3.7m (12ft) in disc width. They are distinguishable from manta rays by their olive-green or brown dorsal surface, but are sometimes mistaken for mantas due to their large size and dark ventral markings.
More about mobulids:
Once thought the be surface-dwellers due to a tendency to gather at the surface in numbers, they have since been documented as the deepest divers among the mobulids, reaching depths of up to 2,000m (6,562ft).
The data were compiled from a range of datasets, including scuba divers, social media platforms, aerial surveys, and reports from fisheries observers, demonstrating the importance of collaborative data sharing and citizen science in the study of rare and endangered species.
‘The original impetus for this study was a citizen science report sent to the Florida Manta Project, which led to sightings in other databases,’ said Pate. ‘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.’
Understanding the distribution of endangered species is crucial for effective management and conservation. The new MMF study sheds light on a potential overlap between the sicklefin devil ray and fisheries in the US Atlantic, highlighting areas where the species may be at greater risk of accidental capture by industrial longlines.
Prior to July 2019, US fisheries observers did not classify accidental catches of rays by species. With accurate species representation in future bycatch data, researchers and conservationists will be able to better understand the impact of fisheries on sicklefin devil rays, in order to make better-informed management decisions regarding their conservation.
‘Little is known about sicklefin devil rays in the United States,’ said Pate. ‘This study highlights how incidental observations and observer data can provide vital knowledge on rare, vulnerable, and difficult-to-study species.
‘We hope this encourages other researchers and managers to examine regional databases for information on other data-poor species.’
This article is edited from the original published on MMF’s website. The complete study, ‘Multiple datasets confirm range extension of the Sicklefin Devil Ray Mobula tarapacana in the western North Atlantic Ocean off the eastern United States,’ by Jessica Pate et al is published in the Journal of the Marine Biological Association of the United Kingdom., Cambridge University Press.