Study by S'pore, US and Indonesia may help manta ray conservation

Scuba divers who often flock to neighbouring countries to dive could, in the future, encounter more manta rays - the gentle giants of the sea - in Indonesian waters.

This is because new research by scientists from Singapore, the United States and Indonesia has uncovered information about them that could help in their conservation.

One important discovery was that the manta rays drawing tourists to popular dive sites - such as Bali and Nusa Penida - travel regularly to other parts of Indonesia, where they are hunted for their meat and gill rakers.

The latter are used in traditional Chinese medicine despite the lack of evidence of their efficacy. This puts at risk Indonesia's manta tourism industry, estimated by authorities there to be worth US$15 million (S$21.2 million) each year.

A paper in the science journal PLOS One in 2013 noted that one manta ray is worth US$1 million in tourism value over its lifetime, compared with US$40 to US$500 if it is hunted and sold for its body parts.

Dr Mark Erdmann, vice-president of Asia Pacific Marine Programmes for the US-based nature group Conservation International (CI), said: "The data has now been shared with the Indonesian government to inform better management and conservation policy and provide even stronger justification to stop the unsustainable hunting.

"(This is) not only for the mantas but also for the benefit of the thousands of Indonesians who depend on manta ray tourism for their livelihoods."

He led the research team, which included staff from CI, Resorts World Sentosa's SEA Aquarium in Singapore, the Indonesian Ministry of Marine Affairs and Fisheries' elasmobranch (sharks and rays) conservation initiative, and the Indonesian Institute of Sciences.

They tagged 33 manta rays with GPS-enabled satellite tags in four regions of Indonesia - Bali, Raja Ampat, East Kalimantan and the Komodo National Park - where these animals gather in large numbers.

They then tracked the movements and behaviour of the rays over a 10-month period starting from September 2014.

The study also uncovered a manta ray nursery in Raja Ampat - the first in South-east Asia.

Juvenile manta rays in the nursery were observed to occasionally venture out of the lagoon, although they eventually return to it.

This finding has already led to a direct conservation action.

The Raja Ampat Marine Protected Area Authority is expected to curtail speedboat use in the nursery.

This will prevent injury and disturbance to the baby manta rays, which tend to stay near the surface and are at risk of propeller strikes from speedboats.

Professor Hari Eko Irianto, director of the Centre for Fisheries Research and Development of the Indonesian Ministry of Marine Affairs and Fisheries, said the project has provided insights that will help Indonesia flourish as an ecotourism destination.

He added: "We are now certain that manta rays migrate across hunting grounds and can increase enforcement in those areas accordingly.

"Through collaborating with local authorities and NGOs, including CI, we plan to undertake continuous monitoring and surveillance to protect mantas, especially juveniles and pregnant females, and their habitats."

This article was first published on January 4 , 2016.
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