Friday, 26 May 2017

Spotted Eagle Ray

By Emily Williams

     The spotted Eagle Ray, Aetobatus narinari, is found in a wide range of locations across the Indo-Pacific, east, and West Atlantic oceans in warm tempered waters. Some evidence suggests that there are at least four probable species of spotted eagle rays but it is still recognized as a single species until further research is done. The spotted eagle ray has been recorded in areas close to shore as well as in the open ocean and can range from swimming at the surface to as far as sixty meters in depth. They are most often observed near shore, around islands and by reefs, but are also believed to be capable of crossing ocean basins.
Female Aetobatus narinari sighted at Looe Key
     Spotted eagles often enter coral reef /environments to feed on benthic organisms including polychaetes, bivalve and gastropod mollusks, cephalopods, crustaceans, and teleost fishes. Fish are an important part of the diet of adult spotted eagle rays. Instead of having teeth, spotted eagle Rays have hardened dental plates that are used for grinding mollusk shells. When feeding, spotted eagle rays submerge their head into the sand to feed and leave behind large holes as they move along the bottom of the ocean floor.
     Spotted eagle rays reach maturity between ages 4 and 6, and are capable of giving birth at that time. The reproduction of A. narinari has not been widely researched but it is known that they can carry one or two pups at a time and gestation is a period of 12 months but may not be annual. This means that reproduction output is limited. A. narinari gives birth to live young which are born with a disc width ranging from 17 to 36 centimeters.
     The spotted eagle ray can reach up to 3.3 meters in disc length but most that are recorded are under 2 meters. They can be black, dark brown, or grey, covered with white spots on its back and a white underside. Their spots are always uniquely placed and can be used as a natural tag for biologists researching them.
     The IUCN identifies the spotted eagle ray as a “threatened species”. The primary threat to spotted eagle rays include fishing pressures, especially in coastal areas. The spotted eagle ray is also a popular candidate for aquariums and is often collected as a part of this aquarium trade. Research is continually being done in order to learn more about this species (or variety of species), and to resolve the taxonomic issue regarding the spotted eagle ray.

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