Stingray census under way

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Update: Department of Environment and Dolphin Discovery staff on Friday morning released back into the wild six stingrays that had been kept in tanks at the dolphinarium.

DoE staff tagged, measured and weighed the rays before lowering each one into the water and setting them free around 9.30am.

The rays – five males and one female – had been transported by wheelbarrow from the tanks at Dolphin Discovery to containers on the back of a waiting DoE truck, which was driven to a dock in West Bay, where the rays were loaded into a large round tank on a boat and then taken to the Sandbar.

Gina Ebanks-Petrie, director of the Department of Environment, said she was pleased the operation to release the rays had gone smoothly, adding that the inclusion of new male rays to the Sandbar could be a boon, as recent checks on the rays show there are very few males among the Sandbar population.

Scientists and vets are doing a head count of Southern Stingrays at the Sandbar this week as they try to gauge if the ray population at the popular tourist attraction continues to decline. 

Two censuses of the rays at the Sandbar done last year showed the number of rays at the site had fallen by about 40 per cent in recent years. 

Meanwhile, the population at the Sandbar looks set to increase by six Friday with the anticipated release of stingrays that had been taken from the wild and housed in tanks at Dolphin Discovery in West Bay. 

The dolphinarium has agreed to release the rays to the Cayman Islands Department of Environment. Earlier this week, vets from Georgia Aquarium, who are in Cayman to help carry out the Sandbar stingray census, examined the six rays at Dolphin Discovery and gave them a clean bill of health to be released back into the sea. 

Three vets from Georgia Aquarium – along with Ioana Popescu from Cayman own’s Island Veterinary Services, staff and interns from the Department of Environment and conservationist Guy Harvey – are spending the week on the water at the Sandbar, tagging and counting the animals, and also taking blood samples. 

They will also be making checks on stingrays at Stingray City and at Rum Point. 

As of late afternoon Wednesday, the team had counted 40 Southern Stingrays at the Sandbar. 

“We’re doing pretty well on the recaptures and extremely well on the new rays; we’re finding juveniles and mid-sized females that we didn’t come across this time last year,” Mr. Harvey said. 

In a departure from checks done in earlier years, this time the team also has an ultrasound machine on board and are checking for pregnant rays. 

Mr. Harvey said he was encouraged by the sighting of previously uncounted rays in the area and also by the number of pregnant females. 

Tonya Clauss, director of animal health at the Georgia Aquarium, who is one of the vets carrying out the census, said, “We’ve found quite a few new animals that we’d never tagged before. We also found some animals that we tagged before but that we didn’t see last year, as well as the recaptures.  

“We have an ultrasound machine with us and we’re doing actual pregnancy examinations with the ultrasound and quite a few animals are carrying pups, while others have very active ovaries and uteruses, meaning they have just pupped or are at the courting stage.” 

Censuses of the Sandbar stingray population have been done in 2002, 2003, 2004, 2005, 2008 and 2012. Between 2002 and 2008, the number of rays found at the site was quite consistent – about 100 each time. However, in January 2012, Brad Wetherbee of the Department of Biological Sciences at the University of Rhode Island, working with the Guy Harvey Research Institute and the Department of Environment on the census, found only 61. When he did another census in June last year, he found 57. 

Subsequent to the June 2012 count, four rays that had been tagged at the Sandbar in the January 2012 census were found in tanks at Dolphin Discovery. The four tagged rays were released in early October last year, but six remained in the tanks as Dolphin Discovery management argued they were not tagged and there was no evidence they or the other four rays had been taken from the Sandbar.  

Dolphin Discovery came into possession of the rays when fishermen who had caught the animals early last year handed them over to the facility in exchange for bait. 

It is illegal to remove stingrays, or any wildlife, from the Sandbar or Stingray City, because both are designated Wildlife Interaction Zones under the Marine Conservation Law.  

Since the rays were found at Dolphin Discovery, the government has passed an amendment to the Marine Conservation Law, making it illegal to remove certain species of rays from anywhere in local waters or to keep those species of rays in captivity. 

Director of the Department of Environment Gina Ebanks-Petrie pointed out that Southern Stingrays are not considered an endangered species and are not subject to conservation concerns in local waters, but that the decline in numbers at the Sandbar needed to be investigated further. 

She said she was pleased the Georgia Aquarium vets were back and that the census and health assessments were under way. “There is a really urgent need to understand in more detail the impact of feeding and human interaction with the rays that is taking place at the Sandbar and what effect it is having on the overall health, reproduction and behaviour of the rays,” she said. 

Ms Clauss anticipates, based on the number of rays counted in the first couple of days of the census that the latest count should be “close or maybe slightly higher than last year”. 

“What’s without doubt is that the numbers are definitely down on what we have seen historically out there. It is still significant,” she said. 

She added: “What we’re seeing with the new inhabitants is encouraging. It’s encouraging to see the animals that have been tagged but that we didn’t see last June. They’ve obviously been moving around, we’re only here a short time.  

“This is still a sensitive population and it is much lower than it used to be in years past. What we are doing out here with the population assessment aspect of it and examining the health and reproductive status is in general to understand what is going on with them and to help sustain the population. It’s important for the animals and for the Cayman Islands and for eco-tourism.”
Results of tests on blood samples taken by the scientists from Georgia Aquarium last year show that the stingrays at the Sandbar are generally healthy, although they could benefit from a more diverse diet than the usual squid that is regularly fed to rays by the thousands of visitors who go to the site every week. 

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A week-long census of stingrays has been taking place off Grand Cayman this week.

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Tonya Clauss uses an ultrasound to check a ray’s condition, with Island Veterinary Services’ Ioana Popescu, holding computer, and Department of Environment research officer Jessica Harvey and DoE student intern Joe Roche Chaloner.

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Tonya Clauss, left, of Ge
orgia Aquarium takes blood from a ray while Island Veterinary Services’ Ioana Popescu assists with the procedure.
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