News
First study of world’s largest marine stingray reveals long-distance migration
Scientists use images and videos submitted by tourists to track rare species in Africa
Smalleye stingrays are the largest marine stingrays on record, reaching disc widths of up to 222 cm, and yet almost nothing is known about them. Scientists from the Marine Megafauna Foundation have for the first time used photo IDs to study this elusive animal in southern Mozambique, one of the only locations where it is regularly seen in the wild. Their findings were published in the journal 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”, said Dr Andrea Marshall, co-founder and principal scientist of the Marine Megafauna Foundation. 31 percent of the world’s sharks and rays are threatened with extinction according to the IUCN Red List of Threatened Species ‒ due to lack of scientific effort and information, it has not been possible to evaluable the conservation status of smalleye stingrays to date. “This species of ray is likely in trouble too but we can’t protect what we don’t know much about. Our study is an important first step in understanding more about the animal’s ecology and behaviour“, she added.
“These mysterious giants are thought to be patchily distributed across the Indian Ocean and Western Pacific, but southern Mozambique is probably the best location to encounter them on inshore reefs”, Marshall added.
Diver and smalleye stingray (c) Andrea Marshall, Marine Megafauna Foundation
The marine biologists tested whether photographs of the stingrays’ (Megatrygon microps) white dorsal spots could be used to distinguish and track individuals over long periods.
“Through local dive centers, we called on tourists to help us collect images of this solitary stingray. Fortunately for us, southern Mozambique and its rich marine life attract many passionate scuba divers, most of which own GoPros or other lightweight cameras and will happily make their images and footage available for research”, said Atlantine Boggio-Pasqua who volunteered with the Tofo-based foundation.
She added: “Their contributions proved immensely valuable, we managed to gather more than 140 photographs suitable for comparison and identification, with some images dating as far back as 2003.”
The team was able to visually identify 70 different individuals, including 15 that had been seen on several occasions in the area. The dorsal spot patterns looked unchanged over the years indicating they may be permanent markings like in manta rays.
Boggio-Pasqua said: “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. 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.”
The encountered stingrays were often spotted at cleaning stations where reef bannerfish and other small fish appeared to be removing parasites from the rays’ skin.
The photographic study also provided a glimpse into the migratory behaviour of Megatrygon microps. Some individuals traveled hundreds of kilometers along the coastline, including a near-term pregnant female which traveled from Tofo to the Bazaruto Archipelago and back (200km in a minimum of 102 days and a total 400km return trip). She returned to Tofo, no longer visibly pregnant, suggesting this individual had pupped during her journey.
This proved to be the longest straight-line distance ever recorded for any species of whiptail stingrays (Dasyatidae family). Unlike other stingrays, smalleye stingrays are rarely seen resting on the seabed and are thought to be semi-pelagic.
Fishermen with smalleye stingray (c) Andrea Marshall, Marine Megafauna Foundation
Smalleye stingrays are likely under threat from increasing fishing pressures. Targeted and incidental catch in coastal gillnets and industrial purse seiners operating offshore are an ongoing issue in Mozambique.
“There are so many questions that remain unanswered about this rare species. 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”, concluded Dr Marshall.
Addressing the lack of available data will eventually allow scientists to formally assess the species’ conservation status in the IUCN Red List and inform management practices.
The study by Atlantine Boggio-Pasqua, Anna Flam and Andrea Marshall, titled ‘Spotting the “small eyes”: using photo-ID methodology to study a wild population of smalleye stingrays (Megatrygon microps) in southern Mozambique’ is published in the journal PeerJ on 11 June 2019 and is freely available here.
For more information about the work of the Marine Megafauna Foundation visit their website by clicking here.
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Jake Davies boards Ghazala Explorer for an unforgettable Red Sea diving experience…
Overnight, the wind picked up, making the planned morning dive a bit bumpy on the Zodiacs to the drop point on Thomas Reef. There, we would dive along the reef before descending through the canyon and then passing under the arch before ascending the wall with a gentle drift. The site provided great encounters with more pelagic species, including shoals of large barracuda, tuna, and bigeye trevally.
Once back on the boat, it was time to get everything tied down again as we would head back south. This time, with the wind behind us, heading to Ras Mohammed to dive Jackfish Alley for another great gentle drift wall dive before then heading up the coast towards the Gulf of Suez to moor up at the wreck of the Thistlegorm. This being the highlight wreck dive of the trip and for many onboard, including myself, it was the first time diving this iconic wreck. I had heard so much about the wreck from friends, and globally, this is a must on any diver’s list. Fortunately for us, there was only one other boat at the site, which was a rarity. A great briefing was delivered by Ahmed, who provided a detailed background about the wreck’s history along with all the required safety information as the currents and visibility at the site can be variable.
Kitting up, there was a lot of excitement on deck before entering the water and heading down the shoreline. Descending to the wreck, there was a light northerly current which reduced the visibility, making it feel more like the conditions that can be found off the Welsh coast. At 10m from the bottom, the outline of the wreck appeared as we reached the area of the wreck which had been bombed, as our mooring line was attached to part of the propeller shaft. Arriving on deck, instantly everywhere you looked there were many of the supplies which the ship was carrying, including Bren Carrier tanks and projectiles that instantly stood out.
We headed around the exterior, taking a look at the large propeller and guns mounted on deck before entering the wreck on the port side to take a look in the holds. It was incredible to see all the trucks, Norton 16H, and BSA motorcycles still perfectly stacked within, providing a real snapshot in time.
Overall, we had four dives on the Thistlegorm, where for all of the dives we were the only group in the water, and at times, there were just three of us on the whole wreck, which made it even more special, especially knowing that most days the wreck has hundreds of divers. Along with the history of the wreck, there was plenty of marine life on the wreck and around, from big green turtles to batfish, along with shoals of mackerel being hunted by trevally. Some unforgettable dives.
The final leg of the trip saw us cross back over the Suez Canal to the Gobal Islands where we planned to stay the night and do three dives at the Dolphin House for the potential of sharing the dive with dolphins. The site, which included a channel that was teeming with reef fish, especially large numbers of goatfish that swam in large shoals along the edge of the reef. These were nice relaxing dives to end the week. Unfortunately, the dolphins didn’t show up, which was okay as like all marine life they are difficult to predict and you can’t guarantee what’s going to be seen. With the last dive complete, we headed back to port for the final night where it was time to clean all the kit and pack before the departure flight the next day.
The whole week from start to finish on Ghazala Explorer was amazing; the boat had all the facilities you need for a comfortable week aboard. The crew were always there to help throughout the day and the chefs providing top quality food which was required after every dive. The itinerary providing some of the best diving with a nice mixture of wreck and reef dives. I would recommend the trip to anyone, whether it’s your first Red Sea liveaboard in the Red Sea or you’re revisiting. Hopefully, it’s not too long before I head back to explore more of the Red Sea onboard Ghazala Explorer.
To find out more about the Northern Red Sea reef and wrecks itineraries aboard Ghazala Explorer, or to book, contact Scuba Travel now:
Email: dive@scubatravel.com
Tel: +44 (0)1483 411590
Photos: Jake Davies / Avalon.Red
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