The Magnificent White – Spotted Eagle Ray (Aetobatus narinari)
Raphaela Stimmelmayr and Maureen SullivanWhite-spotted eagle rays from the Central Atlantic lineage are no strangers to Caribbean waters. All eagle ray subspecies (Eastern Pacific, Western/Central Pacific, Central Atlantic) prefer warm waters and are found throughout tropical waters. Although a primarily pelagic species that can travel long distances across open water, they foray into shallower waters for feeding and giving birth. With a possible wingspan of up-to 2.5 meters and a weight of up-to 150 kg, White-spotted eagle ray make an impressive and startling appearance with their white pattern on the dark background. Granted, the average size of spotted eagle rays in St. Kitts’ waters is only around 1.30m with a weight of around 30kg, but we all know that underwater, everything looks bigger. I still remember well my first encounter with a spotted eagle ray.
I was taking my very first snorkel at South Friar’s Beach up at Olivia’s. The water was choppy and the visibility wasn’t great, and I wasn’t further away from the beach than about 15 yards, when out of the cloudy water alongside the shallow coral reef a large white–spotted eagle ray flew towards me. About a yard separated us and our eyes locked for a brief moment, then we both dashed in opposite directions. My heart was still pounding when I reached the beach.
Eagle rays are generally shy and not easily approached, so encounters are usually brief, but they leave a lasting impression. Like a giant bird, they use their wide wings in upward and downward strokes to glide effortlessly through the blue water column. During spawning and birthing time or when pursued by a shark, they are known to leap out of the water; it’s a sight to behold when this elegant rhomboid-shaped fish with its long whip-like tail goes airborne for a brief moment to then reenter the water with a big loud splash.
The majority of eagle rays observed in the warm waters of St. Kitts occur around the Southeast Peninsula. There we have spotted single adult individuals year round at Majors Bay, Timothy Beach, South Friars beach, and Cockleshell Bay, but never schools of rays. One time we were extremely lucky and spotted a pair of foraging youngsters at Timothy Beach.
Sightings of juveniles in the wild are very rare. Female eagle rays give birth to live young (1-4 neonates) that look just like the adults apart from the smaller size (around 25 cm). Like many shark babies, eagle ray babies and juveniles use near-shore shallow bays/lagoons as safe nursery habitats. However, their slow growth combined with low reproductive rates makes white spotted eagle ray populations quite vulnerable, and the species has been listed by the IUCN as near threatened.
Apart from local fishermen and accidental bycatch, their greatest threats are Carcharhinus leucas predation by sharks, such as the Great Hammerhead (Sphyrna mokkarran), the tiger shark (Galecerdo cuvier), the bull shark (Carcharhinus leucas), and the lemon shark (Negaprion breviostris). Eagle rays themselves forage on a wide variety of small marine organisms. Juvenile conch, clams, crabs, juvenile lobster, sea urchins, squid, and even small coral reef fish are all items on a ray’s meal plan.
When searching for food, rays rely on a sophisticated electro reception system similar to the ones in sharks and other rays to detect the electric currents of suitable prey hidden under the sand. Crushing the shells with their row of plate-like teeth, they only swallow the soft fleshy parts of their prey. Feeding on invertebrates that live on, in, or near the seabed, eagle rays channel this energy to the top predators like sharks that feed on them.
Thus with its intermediate position in the marine food web, eagle rays, like other ray species, such as the southern stingray (Dasyatis americana), a common species around St. Kitts, play an important part in the stability of the local marine environment. A population change or health change among some of these many players has thus far reaching consequences for the dynamic balance of this delicate marine interdependence. With this in mind, we all need to engage in sustainable clean practices, whether we live off the ocean or just come to visit and relish in its splendor.
Raphaela Stimmelmayr and Maureen Sullivan, St. Kitts Reef Ecology Watch Group email@example.com
Photo: http://www.elasmodiver.com. Copyright Andy Murch