Unveiling South Africa’s Giant Rays: A Call for Conservation

While South Africa is renowned for its Big 5, few realise the country is also home to the world’s largest rays: manta rays. These intelligent filter feeders, which sustain themselves on zooplankton, are essential to maintaining ocean health. Beyond their ecological significance, manta rays have the potential to boost tourism revenue, yet they face growing threats from unsustainable fishing practices and human activity.

A nationwide collaborative study by marine biologists has revealed fascinating insights into South Africa’s manta rays, shedding light on these gentle giants and their role in the ecosystem.

Discovering South Africa’s Manta Rays

“Most South Africans don’t realise they can see manta rays without leaving the country,” says Dr Michelle Carpenter, a collaborator with the Marine Megafauna Foundation (MMF), Clansthal Conservancy, and Manta Trust. South Africa is home to two species:

• Reef manta ray (Mobula alfredi)
• Oceanic manta ray (Mobula birostris), the largest ray in the world, with a wingspan of up to 8 metres.

Sadly, human activities have caused a significant population decline, making South Africa’s mantas the most threatened population globally. Both species are listed as endangered on the IUCN Red List. Threats include:

• Trawling
• Tuna purse seine nets
• Gill nets in Mozambique
• Shark nets in South Africa
• Seismic testing by oil companies

Key Findings of the Manta Study

The study, conducted by a team of marine biologists, uncovered several unique characteristics of South Africa’s mantas:

• Reef mantas exhibit high mobility.
• Rare melanistic oceanic mantas (entirely black) were observed.
• Newly identified feeding aggregations and potential baby manta nurseries were found.

Discoveries at iSimangaliso Wetland Park

iSimangaliso Wetland Park, a marine sanctuary in northern KwaZulu-Natal (KZN), emerged as a critical habitat for manta rays. The park, protected from fishing and recreational diving for over 50 years, accounts for 89% of South Africa’s reef manta sightings.

“This aggregation area within a restricted-access sanctuary is a haven amidst threats along the coastline,” explains Nakia Cullain of the Marine Megafauna Foundation. In iSimangaliso, mantas feed and have parasites removed by cleaner fish, demonstrating the sanctuary’s vital role.

iSimangaliso is one of several Mission Blue Hope Spots along South Africa’s coast, joining others like Aliwal Shoal and Cape Town. These areas showcase the effectiveness of marine protection, offering a model for regions like Mozambique that lack extensive marine safeguards.

Manta Ray Connectivity and Movements

Research revealed significant connectivity between South Africa and Mozambique, highlighting the need for cross-border conservation strategies. Key findings include:

• A manta travelled 1,305 km multiple times between Zavora, Mozambique, and iSimangaliso.
• Another covered 600 km from Pondoland MPA to iSimangaliso.
• Juveniles sighted in one region were later observed as adults in another.

“These movements are likely driven by seasonal zooplankton availability,” says Dr Carpenter, who notes that rising ocean temperatures from climate change may be affecting manta movements.

Rare Melanistic Manta Rays

Oceanic mantas are rare in South African waters, with sightings mainly in Ballito, Aliwal Shoal MPA, and Pondoland MPA. Among the most exciting discoveries were rare melanistic mantas, first observed in Aliwal Shoal (February 2020) and Ballito (November 2021).

“It was not previously known that melanistic oceanic mantas inhabited these waters,” explains Dr Carpenter. While genetic studies suggest no distinct population groupings, localised differences in melanism may be influenced by regional groupings and 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, manta rays face threats from fishing, seismic testing, and climate change. Collaborative research efforts and marine sanctuaries like iSimangaliso Wetland Park offer 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.”

By supporting conservation initiatives and protecting these gentle giants, South Africa can ensure its manta rays thrive for generations to come.