While many cite South Africa’s Big 5 as iconic wildlife, few realize that the country is home to the world’s largest rays: manta rays. These intelligent species, which filter feeder zooplankton, play a crucial role in ocean health. The gentle giants hold the potential to drive tourism revenue, but more needs to be done to protect these endangered species from unsustainable fisheries.
A nationwide collaborative study by marine biologists has uncovered some of the mysteries of South Africa’s manta rays, which was released this month. “Most South Africans don’t realise they can see manta rays without leaving the country,” explains Dr Michelle Carpenter, a collaborator of the Marine Megafauna Foundation (MMF), Clansthal Conservancy, and Manta Trust. “We’re home to the reef manta ray (Mobula alfredi) and the oceanic manta ray (Mobula birostris), the latter reaching an impressive 8 metres wingtip to wingtip, making it the largest ray in the world.”
Unfortunately, human impact has resulted in significant population declines, making this the most threatened population of this species in the world. Being listed on the IUCN RedList indicates that this species is globally threatened. Trawling, tuna purse seine nets, gill nets in Mozambique, shark nets in South Africa, and seismic testing by oil companies are all threats to this vulnerable population.
Dr Carpenter worked with a number of dedicated marine biologists on the study. Among them are Dr Ryan Daly (Oceanographic Research Institute), Nakia Cullain (MMF), Dr Andrea Marshall (MMF), Vivienne Dames (South Aquatic Institute for Aquatic Biodiversity), Dr Charles Griffiths (UCT), Grant Smith (SharkLife), and Dr Matt Dicken (Nelson Mandela University).
Oceanic manta rays have a widespread offshore distribution, while reef mantas are more coastal. The study has revealed unique characteristics of South Africa’s mantas, including highly mobile reef mantas, rare black oceanic mantas, newfound feeding aggregations, and potential baby manta nurseries.
Discoveries at iSimangaliso Wetland Park
In iSimangaliso Wetland Park in northern KZN, researchers discovered manta ray feeding aggregations in a marine sanctuary protected from fishing and recreational diving for over 50 years. Here, 89% of South Africa’s reef manta sightings have been recorded, where mantas feed and also have parasites removed by cleaner fish.
“This aggregation area within a restricted-access sanctuary is a haven amidst threats along the coastline,” says Nakia Cullain of the Marine Megafauna Foundation (MMF). “The whole park was recently named a Mission Blue Hope Spot, joining a network along South Africa’s coast that includes Aliwal Shoal and Cape Town.”
Cullain highlights that South Africa’s sanctuary demonstrates how effective marine protection can support, not only manta ray aggregations, but other species as well, providing a valuable model for countries like Mozambique, which currently lacks extensive marine protection.
Manta Ray Connectivity and Movements
Research in iSimangaliso Wetland Park and other areas like Aliwal Shoal has shown significant connectivity to Mozambique.
Some key findings include:
- One manta travelled 1,305 km multiple times between Zavora, Mozambique, and iSimangaliso.
- Another travelled over 600 km from Pondoland MPA to iSimangaliso.
- A juvenile seen in Pondoland MPA in 2016 was later resighted as a pregnant adult in iSimangaliso.
- Two mantas made repeat trips between Zavora and iSimangaliso (870 km round trip).
- 28 mantas were identified in Mozambique, with most linked to Zavora.
“These movements are potentially driven by the availability of zooplankton abundances, which are transient along the coastline and with seasonal patterns,” explains Dr Carpenter. “While mantas have been officially documented in South Africa since the 1950s, shifts in their movements could be linked to climate change, with rising water temperatures affecting currents and food availability.”
Dr Ryan Daly, a specialist in shark and ray movement patterns, emphasises the importance of cross-border conservation efforts: “Because these animals cross borders, conservation management plans need to be aligned between South Africa and Mozambique to protect their populations.”
Rare Melanistic Manta Rays
Oceanic mantas are infrequent in South Africa, with sightings concentrated in Ballito, Aliwal Shoal MPA, and Pondoland MPA. Researchers were even more thrilled to discover rare melanistic (black) oceanic manta rays in Aliwal Shoal MPA (February 2020) and Ballito (November 2021).
“It was not previously known that melanistic oceanic mantas inhabited these waters,” explains Dr Carpenter. “Genetic studies suggest no distinct population groupings, but regional differences in melanism are likely tied to localised groupings, with gene flow facilitated by long-distance travel. We love that these melanistic mantas contribute to South Africa’s beautiful ‘RAYnbow’ Nation!”
Protecting South Africa’s Myste-RAY-ous Giants
Despite their ecological importance, mantas face threats from fishing, seismic testing, and climate change. Collaborative research and effective marine sanctuaries like the iSimangaliso Wetland Park provide hope for their future.
Dr Carpenter concludes: “There is no shortage of work to do with sharks and rays along South Africa’s coastline. I encourage South Africans and international students eager to make a difference to join us. It’s hard work but immensely rewarding.”
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Author: Agnes Matladi from Olivia Jones Communications on behalf of Manta Ray.
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