12 Years of data reveal Seychelles manta ray haunts

Manta rays gather at  D’Arros Island (Amirante Group) and at St. Francois Atoll (Alphonse Group) in the Seychelles, research group reveals after over a decade of study.

Using photo-identification techniques and a novel remote underwater camera system, a team of researchers led by Dr Lauren Peel, aided by citizen scientists, examined the population sizes and frequented areas of reef manta rays (Mobula alfredi) in Seychelles.

Despite increasing pressure from fisheries in the Western Indian Ocean, manta ray populations in Seychelles previously remained poorly understood.

Where in the Seychelles do the mantas go?

Located in the Western Indian Ocean, Seychelles is a remote archipelago of 115 tropical islands. It is divided into the inner, more populous islands, and the more remote outer islands. It is at the outer islands where the manta rays gather, at cleaning stations.

How to identify individual manta rays?

Each manta ray has a unique pattern on its underside. Using photographic identification and GPS position, the researchers could distinguish each one and note where and when they were seen.

Recognising the behaviour of manta rays

 Four primary behaviours were recognised: feeding, courtship, cleaning and cruising.

Feeding

When individual manta rays have unfurled cephalic fins, while swimming with the mouth open, then they are feeding. The rays often formed ‘chains’, swimming in a single file, and sometimes execute backward somersaults through the water column while feeding.

Courting

Courtship was characterised by one or more males actively pursuing a single female, while not engaged in feeding, cleaning or cruising behaviours.

Cleaning Stations

Cleaner fish wait in position over sections of reef. The manta rays linger here while the cleaner fish eat the parasites on their skin. Visits to the cleaning station lasted an average of nearly 5 minutes, although visits lasting 1 minute were the most frequent. The mantas preferred to visit in the middle of the day, between 10 am and 3 pm.

Image: Deposit Photos

Conservation of manta rays

The current lack of a targeted manta ray fishery in Seychelles, coupled with the remote nature of the archipelago and aggregation areas, serves to protect local manta ray populations from the pressures of increased human populations. However, the rays are still caught as by-catch, and get entangled in discarded fishing gear, particularly around the populated Inner Islands where fishing pressures are greatest.

It is hoped that the Marine Spatial Plan, announced by the Government of Seychelles in 2020 will give some protection to these vulnerable animals.

Further Reading

Peel, L.R., Meekan, M.G., Daly, R. et al. Remote hideaways: first insights into the population sizes, habitat use and residency of manta rays at aggregation areas in Seychelles. Mar Biol 171, 83 (2024). https://doi.org/10.1007/s00227-024-04405-6