Raja Ampat, Indonesia, a key nursery for young reef mantas

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  • Scientists have published new evidence confirming that Wayag Lagoon in Indonesia’s Raja Ampat archipelago is a globally rare nursery for juvenile reef manta rays (Mobula alfredi).
  • Visual observations from 2013 to 2021 show that juvenile reef manta rays are repeatedly encountered in the small, shallow, sheltered lagoon, without the presence of adult individuals; young rays spend months at a time inside the lagoon, never venturing outside.
  • The findings have prompted Indonesian marine authorities to begin revising lagoon management to safeguard the nursery grounds for manta rays, with regulations being drafted to limit disturbance to young rays.
  • Oceanic and reef manta rays are protected species under Indonesian law, which prohibits their capture and trade in any part of their body.

JAKARTA – Researchers have confirmed that a lagoon in the Indonesian archipelago of Raja Ampat, a popular dive site, is a nursery for newborn and juvenile manta rays, bolstering the region’s status as a key sanctuary for the ‘species.

In a recently published study, scientists from Indonesia, Australia and New Zealand concluded that the Wayag Lagoon in Raja Ampat, West Papua Province, is a globally rare nursery for reef manta ray juveniles (Mobula Alfredi). Nurseries identified for stingrays generally lack evidence of long-term and continuous stays by juveniles, which is one of three requirements – described in a 2007 study – to confirm a nursery. Other requirements include frequent encounters with young stingrays and repeated use of the site by juveniles.

Wayag is just one of four areas in the Raja Ampat archipelago that have been identified as potential Mr Alfredi nurseries, and is the most studied. If the other three are also confirmed by scientists, it would boost the status of at least two Indonesian protected areas – Raja Ampat and Komodo National Park – as key sanctuaries for manta rays.

“Around the world, there is a lot of work to be done to confirm and protect manta ray nurseries, and I hope this study will encourage researchers and conservationists to undertake more of these projects,” said said the study’s lead author, Edy Setyawan, a marine scientist at the University of Auckland, said in a press release.

Wayag Lagoon in the Indonesian archipelago of Raja Ampat. Image courtesy of University of Auckland.

For their study, Edy and his colleagues analyzed a dataset of visual sightings from 2013 to 2021 showing that juvenile reef manta rays were repeatedly encountered in the small, shallow, sheltered lagoon, without the presence of adult individuals. They combined this with satellite and acoustic tracking data, which showed how young stingrays spent months at a time inside the lagoon, never venturing outside.

Wayag Lagoon is located within the Raja Ampat Marine Protected Area, which guarantees stingrays access to feeding grounds and so-called cleaning stations – sites on coral reefs where small fish “cleaner “feed on the parasites that cling to the rays. At the same time, Raja Ampat is home to many fishing communities and is also a popular destination for foreign tourists, who come for its diving, snorkeling, bird watching and island hopping activities.

Setyawan said Indonesian maritime authorities are already reviewing the management of the lagoon to safeguard the nursery grounds for manta rays. Among the regulations being developed to this end are a 5 knot (9 kilometers per hour) speed limit for boats in the lagoon and the designation of specific areas where visiting vessels can moor without disturbing the rays. juveniles.

“In the manta nursery area, tourists and visitors will still be allowed to view and interact with manta rays under a strict code of conduct, but no fishing is permitted,” Setyawan said.

“Safeguarding this nursery could ultimately be critical to the survival and recovery of Mr Alfredi people in the region,” the study says.

Examples of juvenile reef manta rays spotted in Wayag Lagoon, Raja Ampat. Image courtesy of Setyawan et al. (2022).
A juvenile reef manta ray observed in the Wayag Lagoon of the Indonesian archipelago Raja Ampat, West Papua province. Image courtesy of University of Auckland.

Other places known to have large aggregations of manta rays include Komodo National Park in Indonesia’s Nusa Tenggara province and the Maldives. The authors of the recent study suggest that New Zealand may also be home to a nursery for globally endangered giant oceanic manta rays (Mobula birostris).

“We have seen pregnant females in New Zealand waters,” Setyawan said in the statement. “Additionally, we have observed courtship behaviors and fresh mating scars on some Hauraki Gulf females, and given the 12-13 month gestation period, it seems likely that if they are regularly in New Zealand waters in the summer they will give birth here.”

Reef and oceanic manta rays are classified as threatened on the IUCN Red List. They are targeted for their gill plates, which are a valuable ingredient in traditional Chinese medicine, or accidentally caught as bycatch.

Indonesia has since 2014 placed both species under protection, making it illegal to catch them or trade in any of their body parts.

Indonesian marine scientist Edy Setyawan. Image courtesy of University of Auckland.

Quotes:

Setyawan, E., Erdmann, MV, Mambrasar, R., Hasan, AW, Sianipar, AB, Constantine, R., … Jaine, FRA (2022). Residence and use of an important nursery habitat, the Wayag Lagoon of Raja Ampat, by juvenile reef manta rays (Mobile alfredo). Marine Science Frontiers, 9. doi:10.3389/fmars.2022.815094

Heupel, MR, Carlson, JK and Simpfendorfer, CA (2007). Shark nursery grounds: Concepts, definition, characterization and assumptions. Advances in Marine Ecology Series, 337, 287-297. doi:10.3354/meps337287

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Article published by Hayat


Biodiversity, Conservation, Coral Reefs, Ecotourism, Endangered, Endangered Species, Environment, Fish, Happy Environment, Marine, Marine Animals, Marine Biodiversity, Marine Conservation, Marine Crisis, Marine Ecosystems, Marine Protected Areas, Megafauna, Oceans, Protected Areas, rays, saltwater fish, wildlife conservation

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