Please select your home edition
Edition
Lloyd Stevenson - Catalyst GT 1456x180px TOP

New stingray study shows sharp decline at Stingray City

by Dr. Guy Harvey on 27 Jul 2012
Alex Harvey, Louisa Gibson and Dr. Brad Wetherbee secure a large ray in a pool in the cockpit of Guy Harvey's Scout while Tonya Clauss prepares to take blood sample. - Stingray City 2012 Census John Bell
In mid-July, personnel from the Guy Harvey Research Institute once again collaborated with the Cayman Islands Department of Environment to conduct the annual census of the stingray population in Grand Cayman. This year, we were joined by three researchers from the Georgia Aquarium, who were on hand to assist with analyzing the overall health of the stingrays.

The situation at the Sandbar in North Sound is unique, with a large number of wild rays that are not fenced or contained but inhabit the shallow clear water with accessibility every day of the year. 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!

From a historical perspective, it is worth setting out the track record of research work conducted on the population of stingrays in Grand Cayman. 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. This has been a very simple and valuable tool to track the life history and growth rates of these animals.


For the period 2002 – 2003, one hundred rays were sampled each month over a three-day period at the Sandbar. The same situation was experienced in a subsequent census conducted by the GHRI in 2005 and 2008. As expected, over time there was recruitment of new (untagged) rays to the Sandbar and loss of individuals due to migration, natural mortality and possibly some predation. 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. In response to the reports, the GHRI conducted a census in January 2012 and sampled only 61 rays in the standard three day research period at the Sandbar, which represents a significant (38%) decrease in number of rays compared to the last census in 2008. Now that we had some hard facts to support the eyewitness accounts, the next logical step was to find out what was causing the decline in population.

The numbers of rays have been constant since research was started in 2002 with recruitment and mortality being well balanced. GHRI personnel ruled out predation by sharks in the January census due to lack of evidence of shark bites (near misses) and the corresponding demise of sharks in the last ten years. However, fishing mortality (intentionally or by accident) is a consideration. I say this because here is no national protection for stingrays - outside of the Wildlife Interactive Zones (WIZ) this species has no protection and can be removed and consumed by residents.

Another possibility for us to consider is the overall health of the rays, which is why GHRI enlisted the support of the Georgia Aquarium veterinary staff for this year’s 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 the team sampled 57 rays (only five males) 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 (two males) and caught three rays (one male) at Rum Point, bringing the total to 71 rays sampled. The low number of males in this year’s sample is definitely cause for concern.

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.

From the blood samples the vets will be able to determine if the (monotonous) diet of squid fed to the rays by the majority of tour operators is affecting the animal’s health. The processing of samples and data will take several weeks. At the end of this process we will have more knowledge about these valuable creatures and how better to manage their supplementary diet and well-being.


Overall, a long-term plan of monitoring the numbers of rays and their health is required. 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 ongoing research of the stingrays’ population status and well-being by releasing funds in the Environmental Protection Fund collected for this purpose.

Trofeo Princesa Sofía Mallorca 2025Selden 2020 - FOOTERSCIBS 2025

Related Articles

New Maxi Edmond de Rothschild gears towards flight
The future 32-metre giant is gradually taking shape, a day at a time In December 2023, Ariane de Rothschild officially announced the start of construction for a new oceanic maxi-trimaran designed to venture ever further along the path towards offshore flight initiated by her predecessor, Gitana 17.
Posted on 5 May
iQFOiL Youth & Junior International Games Preview
Over 200 athletes from 23 nations gather at Lake Garda following a high-level Coppa Italia opener The international iQFOiL Class is surging into the 2025 season with record participation and growing global engagement.
Posted on 5 May
An evening honouring the Vendée Globe heroes
On Saturday, May 10, Les Sables d'Olonne will once again come alive to celebrate On Saturday, May 10, Les Sables d'Olonne will once again come alive to celebrate the epic journey of the Vendée Globe and pay tribute to the skippers of the 2024 edition, during a spectacular evening filled with emotion and festivity.
Posted on 5 May
IMA challenges resume with Sandberg PalmaVela
The event has traditionally started the Mediterranean maxi yacht racing season There was huge anticipation from within the maxi community with Sir Lindsay Owen-Jones' new Verdier 100 Magic Carpet E making her debut at Sandberg PalmaVela that concluded yesterday.
Posted on 5 May
Monnin Victorious in 60th Congressional Cup
Defeating defending champion Chris Poole 3-2 in a closely contested final Switzerland's Eric Monnin and his Capvis Swiss Match Racing Team of Ute Monnin Wagner, Mathieu Renault, Jean-Claude Monnin, Simon Brügger, Julien Falxa, and Maxime Mesnil clinched a long awaited win of the 60th Anniversary Congressional Cup on Sunday.
Posted on 5 May
For the love of slightly larger, even faster boats
Bring it on. No chicken chutes allowed. Celestial, the newest Cape 31 in Oz is up and racing Thank you. You have let For the love of small, fast boats run before the breeze like a superlight planning hull under way too big a kite, with immense sheep in the paddock, and the Sailing Master grasping the flare gun in his pocket... No chicken chutes.
Posted on 4 May
21st Sandberg PalmaVela overall
A breezy finale in the Bay of Palma A thrilling and intense final day at Sandberg PalmaVela was enjoyed with choppy seas and wind conditions ranging from gentle airs to gusts of up to 23 knots. Several broken masts are evidence how tough the day was for some.
Posted on 4 May
2025 ILCA 6 Women's & ILCA 7 Men's Worlds Preview
The eyes of the sailing world will turn to Qingdao, China The eyes of the sailing world will turn to Qingdao, China, from 10-17 May 2025, as the city prepares to host the 2025 ILCA 6 Women's and ILCA 7 Men's World Championships.
Posted on 4 May
52 SUPER SERIES Saint-Tropez Cup overall
World Champions Gladiator score 52 SUPER SERIES season opening win. Britain's Tony Langley and his world champion crew secured overall victory at the first regatta of the five event 2025 52 SUPER SERIES season, the 52 SUPER SERIES Saint Tropez Sailing Week.
Posted on 4 May
Transat Paprec Day 15
As the final sprint begins, reflecting on the unique journeys and experiences Among the 19 duos who set off from Concarneau, 8 are international teams, including 5 from the UK.
Posted on 4 May