By Andrea Marshall, NG Emerging Explorer
Giant manta ray (Manta birostris) at Zavora, Mozambique (Photo by Andrea Marshall)
There are so many mysteries yet to be unraveled when it comes to the ocean. One of them that’s close to my own heart is the secretive life of the manta ray, one of the world’s largest and most majestic fish. I’ve spent the past decade trying to learn more about this elusive animal, but it’s proven quite a challenge. They’re a highly mobile species that never stops swimming—so how on Earth do you learn more about their lifestyle and habits? Luckily for me, I have technology on my side, a huge advantage for field researchers in this day and age.
One of the tools we currently use to track these giant rays is acoustic telemetry, a system that works by attaching small acoustic transmitters to their backs. These small pinger tags are picked up by receiving stations placed down on our inshore reefs. In Mozambique we’ve been using this technology for years, and slowly we’re piecing together the story of their lives along the country’s southern coast.
The reef manta ray, which I differentiated from the giant manta ray back in 2009, appears to be resident to our coastline. This magnificent ray, which swims like a giant underwater bird, has a distinct rhythm to its life. In the mornings it comes close inshore, where it visits cleaning stations to get attended to by small fish. Because they never stop swimming, they’re constantly moving along the great highways of the ocean, migrating from one good feeding area to the next in search of rich patches of zooplankton, the tiny suspended animals in the water column that they feed on. Making a pit stop at a cleaning station is like stopping into a car wash and represents an important daily activity for their health. Tiny fish remove algal buildup and parasites from their skin and help to heal any injuries they may have (e.g. from shark bites).
In the twilight hours most manta rays seems to depart the inshore area and make their way to deeper waters to feed. Today, with the Pristine Seas team, I placed my 50th acoustic tag in Mozambique. I hope that our continued efforts along this coastline will provide a greater understanding of this gentle giant so that we can better manage one of the most important populations for this species in the world—and safeguard one of their last strongholds in Africa.