KZN coast home to endangered rays
THE Aliwal Shoal on the KwaZuluNatal South Coast has recently been found to be home to a number of highly-endangered shortfin devil rays, which use the area as a cleaning station.
KZN diver and PhD student specialising in sharks and rays, Michelle Carpenter, said that Aliwal Shoal has even more diversity in terms of rays than it does sharks.
“At the time, I didn’t realise how many rays lived in and frequented Aliwal Shoal. But I’ve been working on my project for over a year now, which means visiting the site almost daily for field work, and have been overwhelmed by the incredible ray diversity as well as the numbers being encountered.”
Rays are dorsal-ventrally compressed, or flattened sharks, and both sharks and rays belong to the cartilaginous group of marine fishes called elasmobranchs.
Carpenter said the site is fortunate to be home to one of the world’s first discovered devil ray cleaning stations, following another such discovery at Bazaruto Archepelago, off the coast of southern Mozambique.
Cleaning stations are important areas on a reef where a marine animal – such as a ray, turtle, shark or fish – will visit to have parasites removed or wounds cleaned by “cleaner fish”.
These sites function as resting areas and mating grounds for hundreds of marine life species.
Located just 4km off the coast of eMkhomazi, Aliwal Shoal is one of two Marine Protected Areas found in the region.
The other is Protea Banks, which can be found 7.5km off Shelly Beach.
Commenting on shortfin devil rays in particular, Carpenter said it was a massive discovery to find them in such large numbers, considering they are classified as “highly endangered” along the southern African coast.
“Some places, such as Tofo in Mozambique, have experienced a decline in sightings of these rays by more than 90% the past few years. This makes the discovery at Aliwal Shoal that much more profound. But it’s not only the numbers of devil rays, it’s also the diversity of ray species that’s so astounding.”
She said there were common sightings of spotted eagle rays, honeycomb whip rays, reticulate whip rays, leopard whip rays, blue stingrays, blue-spotted stingrays, Jenkins’ stingray, round ribbontail rays, and even the critically endangered white-spotted wedgefish.
Although not seen as regularly, divers can also see giant manta rays, reef manta rays, longhorn devil rays, the enigmatic and under-studied bull rays, as well as the extremely rare bowmouth guitarfish.
“Sharks and rays have two additional senses that we don’t possess,” said Carpenter.
“These are the lateral line which detects water displacement, and ampullae of Lorenzini which detect electric pulses. I find the bubbles generated while scuba diving often scare the ray before it approaches you. In various free-diving encounters I’ve been immersed by a school of 50 devil rays, hugged by a giant manta ray, nearly sandwiched by two barrel-rolling giant manta rays, and been face-to-face with spotted eagle rays. It’s truly magical.”
Carpenter’s fieldwork is supported by several scuba diving operators, sponsors and non-profit organisations, without which she says this sort of research would not be possible.
They include UCT, Freediving South Africa, Agulhas House Dive Centre, Marine Megafauna Foundation, ScubaCo Dive Centre, Blue Ocean Dive Resort and the Rufford Foundation.