Friday, 22 September 2017

Manta rays at Denis Island

What are those big sea animals that looks like underwater war planes? They are pelagic fish and one of the most intriguing species; in fact this spectacular animal is highly tolerant towards humans.

Mantas are here again this year, actively feeding in the shallow waters of Denis Island. From late August a few mantas have been sighted, either by diving hotel guests or by the Denis Island diving and fishing team. An encounter with these amazing creatures is purely fortuitous and never fails to amaze those lucky enough to experience it.

The arrivals of mantas at Denis Island correspond to the abundance of food availability. More recently, all along the northwest beach line of Denis island, washed-up zooplankton has been encountered suggesting its abundance in the region.
Mantas are warm water creatures that swim with their large pectoral fins. They have no venom or spine so they are relatively harmless. There are two species of manta rays. The giant manta (Manta birostris) commonly has a wing span of 4.5m (15 feet) but individuals of 9.1 m (29 feet) have been recorded, and it can weigh up to 3 tons (6,600 pounds. The reef manta (Manta alfredi) is smaller (max disc width recorded: 5 m or 16 feet) and it is commonly found in inshore habitats.
The presence of reef manta rays contributes to eco-tourism in certain areas where divers and snorkelers have the opportunity to dive in close proximity to these majestic fish. However manta rays face a huge number of threats such as fishing (both directed and bycatch), habitat degradation, global warming, pollution, ingestion of micro plastics and poor protection status in most regions of the globe. The IUCN Red List has categorized mantas rays as “vulnerable”.
The Manta Trust investigates movement patterns, feeding ecology and demography of reef manta rays in the Seychelles region. By doing this, we hope to gain a better understanding of the health and size of this manta population, as well as where, how, and why these animals move through the various habitats available to them.
Lauren Peel, a PhD student from the University of Western Australia and associated with the Save Our Seas Foundation/Manta ray project in the Seychelles, is very interested in setting up collaborations with researchers and dive shops across the Seychelles in order to get them to report sightings of  manta rays. This will  be with the aim of obtaining an outlook of their distribution and movement patterns. Individual mantas can be identified through the unique pigmentation patterns on the ventral side of their bodies and it is relatively easy to collect ID photos of them by free-diving down in front of them as they approach and take a photo as they swim overhead.

Recently a video of a manta feeding event occurred in Denis Island was recorded, and allowed us to identify two new manta rays and add them to our database. This is very exciting as we previously did not know that mantas were sighted in this area!

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