Text: Tim Jackson. Photographs: Andrea Marshall. Article from the August 2012 issue of Africa Geographic Magazine.
Wildlife news can leave you reeling. Species become extinct, others are discovered; some even become extinct as they are being recorded by science. In the case of the manta ray, it was thought that just one species existed. In 2009, biologist Andrea Marshall identified a second species off Mozambique.
But there may be more, and she and her team need your help to track them. If you’re a diver in manta territory, your images could help scientists to understand these astonishing creatures. Science editor Tim Jackson hot-footed it to Tofo, in the country’s south, to hear more about Marshall’s work, the MantaMatcher programme and the outlook for manta conservation in the area.
‘There are at least two species of giant mantas,’ says Andrea Marshall, ‘and Mozambique is the only place in the world where both are known to use the same habitat on a regular basis.’ US-born Marshall came to South Africa via Australia to help a colleague in Cape Town who was researching great white sharks, but found the weather so cold that she escaped to the warmer waters of Mozambique to photograph whale sharks. It was to be a one-way trip. She was amazed by her sightings, not just of whale sharks but also of manta rays. Now, 10 years later, she runs the Marine Megafauna Association, based at Tofo on Mozambique’s southern coast.
The reef manta is a smaller, more resident species; the giant manta is migratory
When Marshall arrived she was told it would be impossible to study mantas in the wild. But a combination of bloody-mindedness, naivety and ‘sheer stupidity’ helped her to set the record straight, and in 2009 she announced to the established manta fraternity that they were dealing with two different species of mantas, not just the single giant manta that had been recognised. ‘I get a lot of kudos for what people refer to as the largest species discovery in the past 50 years,’ she recalls, ‘but I was simply in the right place at the right time.’ She estimates that there are about 1 400 mantas living along this stretch of coast.
Citizen Science: Mantamatcher
Mantas have a unique spot pattern on their bellies, like a fingerprint. It doesn’t change with age, so you can use it to identify individuals,’ says Andrea Marshall. ‘I’ve spent the past seven years helping with the design of a global automated matching database for the fish.
Called MantaMatcher (www. mantamatcher.org), it was launched online last year and can be used by both researchers and the public.’ If you upload a manta image to the database, then every time ‘your’ manta is seen, you will be sent an update on its status and whereabouts. Marshall thinks the programme will change the face of manta research collaboration.
‘One of the reasons I want divers in South Africa, in particular, to know about MantaMatcher is that we need more proof that manta rays are widely travelled migratory species. Ultimately, we would like to get mantas listed on the Convention on International Trade in Endangered Species (CITES). That would make selling them difficult,’ she explains.
First, however, we need to gain a better understanding of their migratory abilities. ‘So far I have not recorded any movement of reef mantas into South Africa from Mozambique, although I am convinced they do,’ Marshall explains. It is only with the support of the public that we will be able to solve this mystery. (See ‘Calling all divers’ for details.)
Calling all divers
Your manta images could play a vital role in the conservation of these wonderful marine creatures. If you have photographs, slides or digital images of your sightings, please upload them to MantaMatcher (www.mantamatcher.org).
The new species described by Marshall is the giant manta. ‘The species previously described is the reef manta,’ she explains. ‘It’s a smaller, more resident species, with a more limited range, preferring stable inshore habitats. The giant manta spends time in the pelagic environment – it is migratory.’ In fact, this is one of the few places where the rays use the same habitat.
There are obvious physical differences too. The reef manta is a different colour and has different teeth. And while the giant manta has a tail spine, a throwback to both species’ stingray ancestry, the reef manta doesn’t. (The newly discovered manta is the giant manta ray Manta birostris, but taxonomic protocol dictated that it be given the original scientific name because the known type specimen was also a giant manta. Somewhat unusually, the already-described reef manta was allocated the new species name M. alfredi.)
The stretch of coastline shared by the rays runs from the waters off Vilanculos in Mozambique southwards to the Sodwana Bay and Aliwal Shoal areas of South Africa. ‘It’s a unique situation for mantas and we don’t really know why,’ Marshall tells me. ‘It may be because there are really big eddies that run down the Mozambique Channel, creating a lot of planktonic productivity.’ It appears that the mantas ride the channel to follow the abundance of food.
In Tofo the land juts out closer to the edge of the continental shelf than pretty much anywhere else in southern Mozambique, so the waters here are rich in plankton generated by upwellings in the area. ‘There are important aggregation sites elsewhere in Africa,’ Marshall confirms, ‘but this is the largest we know about.’ It’s also a known breeding ground for the mantas (other sites include the waters off Egypt, Sudan, Tanzania, South Africa, Madagascar and Senegal).
Since Marshall’s pioneering days in Mozambique, visitor numbers to the coast have increased dramatically. ‘I’ve always known that I needed to promote tourism to protect the mantas,’ she says. While she is genuinely happy to see this surge in interest, she acknowledges that the consequences are not all positive. ‘I’m struggling as a biologist,’ she admits. ‘I want to tell people about the other things that are happening. There has been an 85 per cent decline in the sightability of mantas along this coastline over the past 10 years. Their numbers are falling too. Environmental factors aren’t the cause, it’s fishing and tourism. Both have picked up markedly since I started here.’
The figures speak for themselves. ‘In 2003, on any given day, there was an 87 per cent chance that you would see mantas. Now you only have a 30 per cent chance,’ Marshall explains. ‘Back then, the average number you would see on a dive was seven; today you’d be lucky to see one.’ Unexpectedly perhaps, it’s the reef mantas that have taken the flak.
‘We are seeing a decline only in the reef mantas and not the giant species; that’s because the pelagic giants are not resident, whereas the reef mantas are,’ Marshall continues. ‘Whatever is happening here is localised, and I think the culprit is partly tourism.’ The team has documented reef manta individuals migrating from the crowded reefs of Tofo to quieter locations further south, around Zavora, and north around Vilanculos.
Marshall’s message for both dive operators and the government is clear. ‘Diving in Mozambique needs to be more tightly regulated or the mantas will seek refuge elsewhere,’ she warns. She feels that the government is not keen to control it because it’s so lucrative. ‘The politicians are not thinking about the long-term problems or about making it a sustainable, environmentally responsible industry,’ she adds.
And while diving pressure may have convinced some mantas to rethink their neighbourhoods, it isn’t a matter of life or death. But fishing is. ‘The fishing industry along Africa’s east coast is totally unregulated,’ she explains. ‘Foreign fleets abuse the coastline with destructive fishing methods. The rays’ gill rakers are worth a lot in the East, way more than shark fins.’
International trade in gill rakers from Africa is on the rise. ‘I used to perceive fishing’ for mantas as nothing more than subsistence – people were killing them and eating them, end of story,’ Marshall continues. ‘But in recent years I have noticed that the mantas’ gill rakers are being removed. Those parts aren’t eaten locally and it appears that Asian markets are actually sourcing manta gill rakers from Mozambique.’ At the moment this trade is fairly small, but she is concerned that it will expand. ‘We need a better system of law enforcement,’ she reasons.
Mantas are long-lived. The oldest recorded specimens are more than 30 years of age, but they are expected to live to 40 or 50. The species ‘Achilles’ heel is its incredibly slow breeding rate. Producing just a single offspring at a time, a female will have only 16 pups in her lifetime, which means that mantas will take a very long time indeed to recover from overfishing, if they can at all.
While diving pressure may have convinced some mantas to rethink their neighbourhoods, it isn’t a matter of life or death. But fishing is
Did you know?
- A manta’s size is measured as its ‘disc width’ – the tip-to-tip measurement across the pectoral fins (or wings). (Newborns measure about 1.5 metres in width.)
A pregnant manta, like the one pictured on the right, has only one foetus – fecundity rates are low.- Manta mums, like all sharks and rays, offer no parental care.
- It is currently still legal, and profitable, to kill mantas in Mozambique.
- The Convention on the Conservation of Migratory Species of Wild Animals added the giant manta to its appendices 1 and 2 in late 2011, effectively forbidding the harvesting of this species internationally.
- In 2011, the International Union for Conservation of Nature (IUCN) reclassified both the giant manta and the reef manta as ‘Vulnerable to Extinction’ (they were previously listed as ‘Data Deficient’)
The fate of the species may boil down to an economic reality check. ‘A big challenge is convincing the government that mantas are worth more to the country alive than dead. With no mantas people won’t come to dive here and that source of foreign income will dry up,’ says Marshall. According to a recent report by WildAid entitled The Global Threat to Manta and Mobula Rays, the current value of the gill-raker trade is estimated at US$ll-million per year. An international organisation set up to end the illegal trade in wildlife, WildAid also records that the expected value of tourism from manta and mobula rays is US$100-million. The fishery value of a single manta ranges between US$40 and US$500, and that’s obviously a once-off fee. But the tourism value of a single manta over its lifetime is calculated to be US$l-million. Clearly live mantas are worth far more to the economy than dead ones.
‘We need to go through the right channels to make killing mantas here illegal,’ urges Marshall. ‘It won’t stop the fishing industry, but there’s nothing to deter anyone right now.’ She has been lobbying for legislation to protect rays in Mozambique for about eight years. ‘You know what got the politicians’ attention?’ she asks. ‘I did a preliminary economic study about the people who were coming to Tofo.’
The government officials were unaware that the site is one of the world’s hotspots for mantas and that people were flocking there to see them. Mozambique is one of the biggest ocean destinations in Africa. It needs to invest in marine safaris and tourism for the future.
‘If the Mozambicans protect their incredible fishery and tourism resources and use them sustainably, they will be able to depend on them for a long time,’ Marshall continues. ‘Instead they’re selling off their rights and those resources are going to disappear.’
Marshall’s dream is the development of a Marine Protected Area (MPA) specifically for mantas and whale sharks. Sited where most of the rays are aggregated, it would stretch 200 kilometres from Vilanculos south to Zavora, incorporating three components. She explains, ‘We already have the research programmes in place, both for now and into the future. We’re collaborating with Ocean Revolution, a US-based NGO that works to integrate the needs of indigenous communities into conservation programmes across the globe. The plan is for the MPA to be a community-run protected area. We also need to teach local fishermen to become marine conservation rangers instead.’
Time will tell whether Marshall’s dream will turn into a reality, and whether both the fishing and dive industries can be effectively controlled to protect Mozambique’s iconic marine species.
Go online
Visit the Marine Megafauna Association www.marinemegafauna.org to read more about its work or to adopt a manta.
Find out what Ocean Revolution is doing to integrate the Mozambican community into manta conservation at www.oceanrevolution.org
You’d be amazed at the ‘facts’ people think they know about mantas, which simply aren’t true. Read Tim Jackson’s blog ‘Mantas are not colour-blind and other manta myths’ at http://bit.ly/RMT30i
