A new census at Grand Cayman’s stingray interactive sites, Stingray City and the Sandbar in the North Sound, is to be undertaken by the Guy Harvey Research Centre next year.
Guy Harvey at work in his art gallery and shop in George Town Photo: Cliodhna McGowan |
By the time the new study comes around in April or May, it will have been four years since the first study at those sites was completed. The two-year study began in 2002.
‘It’s been a long time since then,’ explained marine biologist, marine wildlife artist and conservationist Guy Harvey.
A new study would show which animals are there, which are not there, and how many new ones have been recruited at the sites, he said.
‘We expect there to have been changes within the population by not only the composition of males and females due to constant recruitment of new animals, but we’ve also experienced a catastrophic event, which is Ivan, and nobody really knows what effects that had on the stingray population.’
Director of the Guy Harvey Research Institute based at Nova South Eastern University, Fort Lauderdale, Professor Mahmood Shivji said that they determined the size of the stingray population at the interactive sites in the study, but anecdotal observations by the Grand Cayman dive and snorkel operators suggest that the stingray population became considerably reduced since Hurricane Ivan.
During the study, all the animals were tagged with pit tags (an internal passive tag read by a scanner). It also included the rays being measured, having wing clips taken (for DNA and also as a marking that the ray has been tagged etc) and having their movements tracked at night.
They tagged 165 animals in the sandbar, 22 from the stingray city site and 45 wild animals from around Grand Cayman that don’t interact with humans, as a control.
‘The wonderful thing about the original study is that there is now a baseline of information for future studies,’ Mr Harvey said.
The Department of Environment’s Assistant Director – Research and Assessment Tim Austin said that although the new study has yet to be formally approved by the Marine Conservation Board, he believes it will be beneficial. ‘Without wide consultation, my opinion would be that DoE would welcome the study in order to update previous work by GHRI as well as supplement other ongoing research into the population dynamics, ecological health and social aspects of the sandbar and stingray city experiences’.
The GHRI funds the study and the DoE provides logistical support through use of its visiting scientist accommodation, DoE lab facilities, DoE staff time and boat and vehicle support if required.
Useful Information
Mr. Austin noted that information from the last study was indeed useful and some aspects of it were incorporated into new regulations, now being enforced, which designate both the Sandbar and Stingray City as Wildlife Interaction Zones.
The first study was the first confirmation of how many rays were at the various sites and it showed the range the rays covered in their daily movements. ‘This was important as it helped to determine the required size of the various WIZs and allowed the DoE to compromise its stated position of no more additional stingray feeding sites and allow potential sites within the boundaries of the WIZ as these would be the same rays and no new population of rays would be impacted.’
Additionally, he said, the GHRI made recommendations that footwear should not be allowed in the shallow sandbar as their studies confirmed an abundance of human induced injuries to rays from footwear. So, this was incorporated into the WIZ regulations.
Study Findings
One of the outcomes of the first study showed that the growth rates of the control group of wild stingrays were slower than the growth rate of the animals at the sandbar that were constantly being fed.
Another finding was that the reproductive rate of the animals at the sandbar was year-round instead of a discreet period which is normally in the summer.
A major finding included the interactive sites rays’ behaviours being altered from that of wild rays, especially the larger females.
Mr. Harvey explained, ‘They are predators, carnivorous animals, and they typically hunt at night-time and we reversed that behaviour by feeding them in the daytime and at night time we found that they would basically lay down in the shallows around the sandbar and do nothing.
‘So while the pattern was that the females did not move far away from the sandbar at night-time, the males, which are much smaller, and not nearly as successful at feeding as the big animals, because they get pushed off the sandbar, went to forage at night time.’
The males were found to move two or three miles on an average night, looking for food, which is normal behaviour, so Mr. Harvey noted that humans have not prevented their ability to forage for themselves.
‘I view these things as a tool for educating people about marine life and a unique opportunity for scientific study,’ he said.
Mr. Harvey believes it is of the utmost importance to keep track of what is happening with the rays in the interactive zones.
‘It’s such an important asset for the Cayman Islands so we need to be informed about the population changes,’ he said.
Those who don’t approve of the interaction with the rays use the argument that they have become dependent on people, said Mr. Harvey, but the study proved that is not so, that they feed normally, they are just adding to their diet by interacting with people. However, the larger females are more conditioned to human interaction than the smaller rays because they are more successful at the sandbar in competing with the other animals to get food.
Because the study had shown they can still forage, Mr. Harvey said that after Ivan he had no concerns that the animals wouldn’t survive on their own without constant attention from people.
He noted that despite a negative effect from the death of Steve Irwin a year ago in a freak accident involving a stingray, and some being unjustifiably apprehensive about interacting with stingrays, Grand Cayman’s is still a popular marine interactive programme in the world and so it needs to be treated with respect.
Next year’s study should take less than a month to do because it’s not the same behavioural study as last time, but more of a census. Like the previous study, it will be filmed and is to feature in Mr. Harvey’s TV series Portraits from the Deep.
Regulations
All commercial boat operators are now required to have a licence to visit the Sandbar and deep Stingray City, under the new WIZ regulations brought about to better regulate the two stingray sites in the North Sound.
Conditions attached to the licences also include restrictions on feeding the rays at the WIZs: only one designated staff member may feed the fish; and for each trip only a maximum of 1lb of approved food (including balyhoo and squid) may be used.
The number of people visiting that sandbar at any one time is also now limited on licensed vessels: no more than 100 people per trip per boat; no more than 1,500 people in the area; no more than 20 licensed tourist boats in the area.
Mr. Austin noted that commercial operators have been very co-operative in submitting the necessary documents and fees in order to apply for their licences.
The DoE is gradually phasing in full enforcement of the WIZ regulations and will begin stepping up enforcement at the end of September although routine patrols are occurring now. ‘Boats are being informed of the need to fully comply by September or face potential warnings or even prosecution,’ he said.
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