American rays set up home off Bermuda
A new species of ray has settled in island waters, the Department of Environment and Natural Resources said yesterday.
Mark Outerbridge, a senior biodiversity officer at the department, said in the latest Envirotalk newsletter it appeared that a population of cownose rays from the US had become permanent residents.
Dr Outerbridge added: “A migratory school originating from the eastern seaboard of the USA likely took a wrong turn somewhere and ended up bumping into Bermuda.
“Anecdotal evidence suggests that it was a small school that arrived in 2014 or 2015.
“It appears that the founding rays decided to remain here rather than take the risk of returning the way they came.”
Dr Outerbridge said that reports of cownose rays in the Great Sound became increasingly common and in November one was seen at Flatts Inlet attempting to swim into Harrington Sound against the current.
Dr Outerbridge said: “It looks as if the cownose rays are here to stay.
“Residents are sighting them more and more, and DENR has received at least one report of a birthing event, so it is expected that the local subpopulation will grow over time in abundance and distribution.”
He added: “It remains to be seen how this new species of inshore ray will affect Bermuda’s mussels, oysters, calico clams, and conch.”
Bermuda was known to have two resident species of rays – spotted eagle rays, which are found inshore, and manta rays, which live in the open ocean.
But the DENR got reports of “unusual rays” in Mill’s Creek that were smaller than spotted eagle rays and lacked their distinctive spots in early 2015.
Dr Outerbridge said: “Another member of the public subsequently managed to photograph two individuals on the surface of Mill’s Creek, at which point the DENR was able to positively identify them as cownose rays.
“Cownose rays belong to a group of fishes that includes the eagle rays and the manta rays.
“They have a broad, lumpy head which, when viewed from above, somewhat resembles the nose of a cow.”
He said the rays were usually brown or olive green with a pale belly and barbed spines where their tail met their body.
Dr Outerbridge added: “Adult females normally attain a wingspan of about three feet and weigh up to 50 pounds, versus spotted eagle rays, which are twice that size and at least three times the weight.
“Cownose rays are native to the western Atlantic basin and usually live in shallow marine coastal waters.
“They are known to swim in large schools – sometimes numbering thousands of individuals – and migrate long distances throughout their range.”
Cownose rays eat clams, oysters and large marine snails and schools have been blamed for huge reductions in shellfish populations in some areas.
Dr Outerbridge said: “Some fisheries scientists believe that this may have happened because of the significant decline in shark populations.
“Decades of fishing has led to an alarming depletion of shark species worldwide.
“Sharks prey on rays and thus control their number and influence behaviour, such as foraging.
“The loss of the sharks has enabled some ray populations to grow in size and feed in an unregulated manner. The very same dynamic may be happening locally with green sea turtles and our declining seagrass meadows.”
Dr Outerbridge added that anyone interested in seeing a cownose ray up close should visit the Bermuda Aquarium Museum and Zoo, which has had one in the North Rock tank since March.