A record 113 stingrays were counted at the North Sound Sandbar during the latest census, according to the Guy Harvey Ocean Foundation.
Despite the encouraging news, researchers remain concerned about increasing boat traffic, overcrowding and the mishandling of rays at the popular attraction.
Mr. Harvey’s research organization has been carrying out population surveys at the Sandbar since 2008, and conducting biannual head counts since 2012.
Louisa Gibson of the foundation said this year’s total was the highest ever recorded. She said numbers had dipped as low as 57 in 2013, and credited the introduction of the National Conservation Law, which includes protection for rays, as one of the key reasons for the resurgence.
Before that she said there had been incidents of people fishing or stealing the rays and selling them to attractions.
Ms. Gibson said that did not appear to be an issue any longer, and the population had been on a generally upward trend since 2014.
“The population is stable at around 100, and seems to be increasing,” she said.
“We do need to look at the food they eat and how the stingrays are handled.”
Tour guides typically allow tourists to feed squid to the rays, but based on concerns raised by scientists during previous surveys, the Department of Environment is encouraging them to diversify that diet to include crab and fish – more natural food sources for rays.
The latest survey was carried out over three days, Thursday through Saturday, earlier this month. Researchers catch the rays by hand, swim them into a salmon net and lift them on board where they are transferred to a paddling pool, while the team takes the vital measurements and checks for tags.
Any new rays are tagged before they are returned to the water, to aid future counts.
This year there were 98 “resident” rays at the Sandbar that had been tagged previously and 15 newcomers.
Visiting scientist Dominique Keller from Busch Gardens, Tampa Bay, carried out an ultrasound on the rays and found that 24 of the 90 female rays at the site were pregnant. This is significantly lower than on previous occasions, and the research team hopes to make ultrasound checks a more regular part of the surveys to see if any pattern can be established.
The Guy Harvey Ocean Foundation estimates each stingray is worth more than $500,000 a year to the Cayman Islands economy because of the enduring popularity of the Sandbar.
Ms. Gibson said it was important for the health of the rays and for the quality of the experience at the Sandbar that issues like overcrowding and the proper handling of rays are addressed. The foundation will collaborate with the DoE on various measures, including a video for tour guides on the right way to handle the animals.
“We don’t want the rays being lifted out the water, we don’t want them being manhandled,” she said.
“It is important that the tour operators do self police and look out and see that people are handling them the right way.”
Tim Austin, deputy director of the Department of Environment, said the new guidelines could be embedded in a species management plan and regulated through the National Conservation Law.
Activity at the Sandbar is currently regulated through the Wildlife Interaction Zone guidelines.
Mr. Austin said there was a limit of 20 commercial boats or 1,500 people allowed in the zone at any one time. But he acknowledged this was largely self policed by the operators. He said this was an “attraction management” issue that may need to be looked at as tourism increases.
He said more and more boats were registering to go into the zone.
He added, “The rays are an important asset and any activity that goes on around that area from feeding them, to plastic waste and boat handling issues, has potential impacts.”