- The smalleye stingray, thought to be widely distributed across the Indo-West Pacific, is rarely seen and is listed as “data deficient” on the IUCN Red List.
- By compiling photographs and videos of the stingrays taken opportunistically by both research teams and recreational divers over the last 15 years off the coast of Mozambique, the only place the giant rays are regularly spotted, researchers have created a photographic database of the animals.
- This database is now helping researchers gain some of the first insights into this elusive species. For example, researchers found that a female stingray had made a 400-kilometer (250-mile) round trip to birth her pups.
The smalleye stingray may be the largest of marine stingrays, but the species remains a mystery. It’s believed to be widely distributed across the Indo-West Pacific and has been recorded at sizes up to 2.2 meters (7 feet) across. Yet the giant ray is rarely seen and is listed as “data deficient” on the IUCN Red List.
The only place where people do regularly encounter the smalleye stingray (Megatrygon microps) is off the coast of Mozambique. There, researchers first recorded the species’ presence off Tofo Beach in 2004. Since then, they’ve been compiling photographs and videos of the stingrays taken opportunistically by both research teams and recreational divers over the last 15 years, creating an image database of the animal. This database is now helping researchers gain some of the first insights into this elusive species, according to a new study published in PeerJ.
“We reported the first sightings of smalleye stingray in 2004 and have since been racing against the clock to learn more about their ecology before it is too late,” Andrea Marshall, a co-author of the study and co-founder and principal scientist of the Marine Megafauna Foundation, said in a statement. “This species of ray is likely in trouble too but we can’t protect what we don’t know much about.”
The researchers focused on images from three main regions — Zavora, Tofo Beach/Barra, and the Bazaruto Archipelago National Park (BANP) — and found that all smalleye stingrays seem to have uniquely identifiable patterns of white spots on their backs, ones that have remained unchanged over the years. Using these patterns, the research team could identify 70 unique individuals during their study period, mostly from the Tofo Beach/Barra area where recreational divers tend to go.
The team also identified 15 smalleye stingrays that had been seen off the Mozambique coast multiple times. One visibly pregnant female stingray, for example, was first spotted off Tofo Beach in January 2017, then seen again about 200 kilometers (124 miles) away, just south of BANP, some 100 days later. The same female was seen again off Tofo Beach in June 2018, suggesting she’d completed a round trip of at least 400 kilometers (250 miles). This time she was no longer pregnant, indicating she had given birth somewhere along the way.
As more data on these rays trickle in, scientists will eventually be able to assess the smalleye stingray’s conservation status for the IUCN Red List. For now, though, researchers say the species is already likely threatened by fishing activity.
“There are so many questions that remain unanswered about this rare species,” Marshall said. “Where do they live, how fast do they mature and how do they reproduce? Filling these knowledge gaps is crucial to figuring out how to protect them properly in Mozambique and other parts of the Indian Ocean.”
The team says it hopes that more recreational divers and citizen scientists will help fill these information gaps. “Smalleye stingrays may look intimidating at first glance with their large, razor-sharp tail spines, but they’re actually really charismatic and easy to approach,” Atlantine Boggio-Pasqua, a co-author of the study who volunteered with the Marine Megafauna Foundation, said in the statement. “We hope to receive many photo and video contributions from citizen scientists in future. They could tell us more about the species’ habitat preference as well as feeding and cleaning behavior.”
Banner image of a diver and a smalleye stingray by Andrea Marshall/Marine Megafauna Foundation.
Citation:
Boggio-Pasqua, A., Flam, A. L., & Marshall, A. D. (2019). Spotting the “small eyes”: Using photo-ID methodology to study a wild population of smalleye stingrays (Megatrygon microps) in southern Mozambique. PeerJ, 7. doi:10.7717/peerj.7110