New Study Confirms A World-First International Migration Of Reef Manta Rays

The thunderous sound of the helicopter nearly destroyed the thoughts Marine Megaphone Foundation (MMF) pilot and field researcher Janneman Conradie was having as he looked through his camera lens and spotted a reef radius.Mobula Alfredi) in what he thought was the wrong habitat for them.

It almost ruined the surprise. But not completely.

When he spotted the majestic predator during the aerial transect at the Sardine Run, held annually along the wild coast of South Africa’s Eastern Cape province, nothing could hold back the surprise. Known as one of the world’s most spectacular marine events, the silver sardine migration begins in the cool waters off the southern tip of the African continent, where they congregate into hundreds of chaotic shoals. This swirling mass then heads northeast into the warm waters of the Indian Ocean, giant waves of this tiny fish along with legions of predators such as sharks, dolphins, cape gannets, cormorants, seals, and more. However, after 100 days of flight (resulting in 335 hours of survey time), he was convinced that this was no accident: “At first it didn’t seem like a suitable habitat for them, but as the observation increased, we had to admit We suggest that this area may actually be a nursery habitat for reef mantas, with all individuals encountered less than 2 meters long.

The MMF Manta Ray Research Program in Mozambique has been monitoring this southern Mozambique population for over 20 years, making it one of the longest-running and most comprehensive manta ray studies in the world. Recently, the team has focused on better understanding where and how much this species moves to guide effective management solutions. The largest species of devil ray ( mobula genus), they occur regularly on coastal and oceanic reefs throughout the tropical and subtropical waters of the Indian and Pacific oceans. Previous work frok MMF has shown a sharp decline in sightings of manta rays in Mozambique over the past two decades, highlighting it as an endangered population. Now, long-term monitoring and photographic contributions from the public have highlighted six transboundary movements that provide the first evidence of connectivity between reef ray aggregation sites in South Africa and southern Mozambique. This extends the southern reach of the manta ray reef in Africa, connecting the longest monitored and highly vulnerable population of manta rays in southern Mozambique to the UNESCO World Heritage site iSimangaliso in South Africa.

“As highly mobile species, reef manta rays are capable of long-distance movements, so it was only a matter of time until we documented international exchange between neighboring waters. “We are very excited to have finally confirmed this for the first time through a detailed and long-term research effort along the southeast coast of Africa,” said Dr. Andrea Marshall, one of MMF’s principal scientists who oversaw the project. Dr. Stephanie Venables, who also completed her PhD thesis on Mozambique’s manta ray population, was also excited by the recent findings: “These transboundary movements are an important finding, as they highlight the need for collaborative species management between neighboring countries. it shows. Both scientists emphasize that this latest research supports the Convention on Migratory Species (CMS) listing for reef manta rays, and shows that transboundary management units are warranted for this widespread species.

What makes this discovery especially unique is that the citizen science contributions of the SCUBA diving community helped make it happen! Divers are constantly uploading photos of mantas in South Africa to MantaMatcher.org, a global open-access online database for rays. This database allows cross-referencing of regional databases using automated pattern matching algorithms, which can lead to exciting discoveries…like this one. “Citizen science participation in this research was very important,” says Anna Flamm, Global Director of Manta Matcher. The first two transboundary movements were identified by public submissions to Manta Matcher, showing how people everywhere can contribute to conservation science. Along with opportunistic fieldwork, researchers were able to discover the longest hidden life of these beautiful feeders. Notable discoveries include an individual traveling back and forth between Zavora in southern Mozambique and Sodwana Bay (a total distance of at least 540 miles or 870 km) and the (one-way) movement of another individual traveling between Tofu Coast, Mozambique and . Sudwana Bay, South Africa in less than 301 days – a straight line distance of 313 miles (505 km). And not to forget the reef manta rays spotted during aerial surveys and underwater encounters at the annual sardine race, with their small size indicating a potential nursery habitat in the area.

“South Africa has been a missing piece of the puzzle for some time, and much work is still needed to understand the habitat use of manatee rays here,” says Michelle Carpenter, PhD candidate at the University of Cape Town. “Although we are just beginning to explore the surface of these movements, these findings are a big step in helping us inform . Species Management and Conservation in Southern Africa.”

This study titled “Southern range expansion and transboundary movements of reef manta rays Mobula Alfredi Along the East African Coastline” was published in the December 2022 Journal of Fish Biology and can be accessed here.