Numbers falling at famous Stingray City

| 26/07/2012

SotosE2.jpg(CNS): Research conducted by the Guy Harvey Research Institute with the Cayman Islands Department of Environment has confirmed fears that the number of Stingrays at the Cayman Islands most popular tourist attraction are falling. The census this year found the stingray population at Stingray City has decreased by around 38% compared to the last census in 2008. The researchers have also raised concerns over the low number of male samples tagged in the most recent analysis and are now trying to find out why the numbers are falling. Blood samples have been taken by researchers to determine if the diet of squid fed to the rays by the majority of tour operators is affecting the animal¹s health. 

“A long-term plan of monitoring the numbers of rays and their health is required,’ said officials from the Guy Harvey Research Institute (GHRI) in a release this week. “Everyone in the Cayman Islands benefits from the presence of this unique marine interactive site. Every advertising campaign or tourism related article featuring the Cayman Islands has these iconic animals up front and prominently displayed. It is time the government of the Cayman Islands returned the favor by supporting on-going research of the stingrays¹ population status andwell-being by releasing funds in the Environmental Protection Fund collected for this purpose.”

The Sandbar in the North Sound has a large number of wild rays that are accessible to tourists every day of the year. As a result the socio-economic value of the rays to the Cayman economy is enormous. On average, each animal can generate up to $500,000 in revenue per year, or $10,000,000 over the course of a 20-year life span.

Research was started by the GHRI in 2002 when all the stingrays that frequent the two main sites were caught by hand and tagged with a PIT (passive integrated transponder) at the base of their tail. During the initial count, 164 rays were tagged, weighed and measured at the Sandbar over two years. Since then, tag retention has remained near 100% so many animals tagged ten years ago still have their PIT today. The sex ratio of 90% females to 10% males has remained fairly constant over this time.

From 2010 tour operators and casual observations indicated a sudden decline in the number of rays at the Sandbar. The GHRI conducted a census in January 2012 and sampled only 61rays in the standard three day research period representing a significant 38% decrease in numbers compared to 2008count.

Armed with this information researchers are now eager to find out what has caused the decline. Predation by sharks has been ruled out for a lack of evidence of shark bites and the corresponding demise of sharks. However, fishing mortality is a consideration as there is no national protection for stingrays – outside of the Wildlife Interactive Zones (WIZ) .
Another possibility is the overall health of the rays, which is why GHRI enlisted the support of the Georgia Aquarium veterinary staff for this year¹s census. The addition of the GA vets also allowed the research work to become much more technical. Dr. Tonya Clauss (Director Animal Health, Georgia Aquarium), Dr. Lisa Hoopes  (Nutritionist, Georgia Aquarium) and Nicole Boucha (Senior Veterinary Technician, Georgia Aquarium) arrived in Grand Cayman loaded with equipment to take blood and store these precious samples in liquid nitrogen until analysis could be achieved back in Georgia.

Over three days in July the team sampled 57 rays only 5 of which were male at the Sandbar down from 61 in January with assistance from DoE staff and several volunteers. The team also spent a day at the original Stingray City and sampled 11 rays , just 2 male) and caught 3 rays at Rum Point, bringing the total to 71 rays sampled. 

Each ray was caught by hand and transferred to the pool in the workboat where they were measured and tagged, and then blood was taken from the underside of the base of the tail. Some of this blood was immediately centrifuged to make counts of white blood cells. The rest was frozen in liquid nitrogen for shipment back to the lab in the Georgia Aquarium.

The processing of samples and data will take several weeks the researchers hope to have a better idea about what is undermining these valuable creatures and how better to manage their future well-being.

Category: Science and Nature

Comments (13)

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  1. Thunder Storm says:

    there'a a predator called "pinos" that eats dem, maybe this is why the numbers are falling

  2. Crabby McGee says:

    Is it legal to fish for stingrays? Maybe people have been trolling the sandbar for supper? BBQ Stingray?

  3. Anonymous says:

    Just another start to putting restrictions on Sting Ray City!

  4. DanDan says:

    I ventured to Stingray city last week wWednesday to visit after not going for many years.

    Can Guy Harvey or anyone else explain to me why all of the stingray barbs were removed?

    It seems cruel and unusual that someone would go out there and do that and I hope it was not done in the name of 'tourism' or 'research'!

     

    • concerned CAYMANIAN TO THE BONE says:

      GUY HARVEY'S INSTITUTE you are business come lately to the famous stingrays in CAYMAN ISLANDS!

      Your research into the stingrays have cause some of the decrease in the species (taking them out of their environment, injecting them, taking blood, and tagging them). I have been frequenting the sandbar since 1968 when this place was home to all species of sea life including some of the most beautiful shells discovered only by using your feet to plow the sandy bottom for these creatures. We cleaned our catch there and no one deared to touch those creatures.

      On my last visit to the famous sandbar I concur with an earlier writer that either the tail or barb or both on many of the rays were removed. To my dismay, I also found two rays with a big chunk from its wing flap in the shape of a shart attack. SO GHI since you are not aware that we have sharks in CAYYMAN and that rays is in the food chain for ther sharks tell me how do you explain why rays are used as the choice baits to harvest sharks? Back in the 1940's, 50's, 60's and early 70's sharks were harvested for their hide, fin and teeth and sold to a big company in the USA.

      Today, the rays is a choice food to many nations and sharks alike. I have personally withnessed a shark chasing a ray at the sandbar. Don't Mr Guy Harvey Institute you have lots to learn about the sea around Cayman. This is not a Sea Equarium enclosed by walls. But is open to many species of sea life including the bottled nose Dolphin, Hammer and Tigar Sharks as well as the White tip and Black Tip shark.

      Go do your research work in the enclosed confines of the Universities and attraction parks Not in Cayman.

  5. Anonymous says:

    Maybe they heard of Bus's next proposal – to tax stingrays who were not born on the island!

  6. Sciencey says:

    Before anyone gets too excited (as if that will happen on CNS), the experts have stated that this may or may not mean anything. Uncharacteristically, they are not calling for extreme conservation measures or anything else.

     

    They are simply noting that unlike falacious claims  of the past, that numbers were declining, formal counts have indeed noted a decline in numbers this year. The reason for the lower numbers is completely unknown and is worthy of further investigation. Full stop.

     

    The rays may be dying, or they may be prospering and have simply gone on holiday. They may even be enjoying a steady stream of squid infused dolphin poo at another location. Until further study finds the real cause, we can only speculate.

  7. Anonymous says:

    I would like to take a time out to explain somthing that should be very clear and simple. this sandbar thing was created by local fishermen who started feeding and getting into the water with them and touching them with experienced hands. This is nothing to do with the facts to be explained, There were numbers and more comming and joinging everyday. Then come along the so called experts "idiots" that will tell you about stingrays and dolphins, how they use radar type technology to meet and communicate around each other. So here this idiots go in the wild and "TAG" this wild animals, have a device that emits some strange signal and expecting the animals to come and go around each other as if everything is normal. Think for a minute you enviroment Idiots, how do you think this animals can come close to each other and pick up a bad vibe from the other animal and not move away, worst if more is closer together. It does not take a so called educated idiot to understand this. Out of stupidity and for a way to make it seem they care. Find and remove the tags and bring live bate that is normal for the animals and you will see them back, Lets hope they dont go and Tag the lone dolphin so that his or her signal can be sent out properly that there is food and shelter in the area,,, so Please understand, the radation power that it take for those things to emit to a satilite in the space above has to be real strong. So naturaly it would affect the natral communication of the animals. If you want to tag somthing tag The Premier and the MLAs so they can be tracked down and found out where they doing and what they doing and when.

    • Dr. Anthony Britsen says:

      In reference to the ridiculous comment by Anonymous 18:23:

      The PIT implants do not emit any form of radiation and cannot affect any other creature.  They are not and cannot be used for tracking.  Perhaps you should do some research on PIT technology before making inaccurate statements.

    • SKEPTICAL says:

      From which seat of learning did you obtain your qualifications in Marine Biology ?

      • Like It Is says:

        This is CNS.  Heaven forbidthat someone asks for the facts or learning underpinning an opinion.  As long as someone has worked on a boat or can misquote an old article in Nor'wester then their opinion is gospel.  Remember anything said by a "Captain" or written in the Nor'wester is true and cannot be challenged.  Got it?

    • Anonymous says:

      Another Caymankind expert at pretending to know what he's talking about.  Run for office.  You will do well.

  8. Mo Money says:

    Expat stingrays,getting out while they can.