August 5, 2016, the adult female tiger shark tagged by LAMAVE and the Tubbataha Management Office (TMO) has transmitted her location beyond the boundaries of the Tubbataha Reefs Natural Park (TRNP).
The female shark, which has been nicknamed #tubbatahatiger is the first tiger shark to be fitted with a satellite tag in the Coral Triangle. The deployment of the tag is part of a study by LAMAVE and TMO to understand more about the range and habitat use of tiger sharks both within the Tubbataha Reefs Natural Park and outside this marine protected area (MPA). The information gathered via satellite will be essential in helping to manage the future of the species within TRNP and the Philippines.
The map gives us an insight into her movements, with each marker representing a transmission sent via satellite each time she swam with the dorsal fin exposed above the surface of the water. The markers located within the park (inside the purple boundary) show that she is moving between both the North and the South Islet as well as further offshore.
While only the beginning of her journey, these results already reveal the importance of developing large marine protected areas, such as Tubbataha Reefs, which offer more complete habitat protection for apex predators such as tiger sharks. However, her journey outside the park implies that if we want to ensure a future for these incredible animals in the Philippines, the species needs to be protected nationwide and not just within marine protected areas such as TRNP, which is currently one of the only places to see these amazing sharks in the Philippines.
Where will she go next? Have you seen a tiger shark outside of Tubbataha Reefs Natural Park? Share your encounter with us and stay tuned for the next ping.
First tiger sharks tagged in the Philippines, Southeast Asia hooked in Tubbataha Reefs
They are hardly found anywhere else in the country, but their presence in the Tubbataha Reefs makes it possible to generate greater understanding of their kind. A team of researchers from the Large Marine Vertebrates Project – Philippines (LAMAVE) and the Tubbataha Management Office successfully tagged two tiger sharks (Galeocerdo cuvier) in the Park during Expedition Shark 2 on 11 to 19 June.
The tiger sharks, listed as Near Threatened (NT) in the IUCN Red List of Threatened Species, were both caught in successive days in the South Atoll off the Delsan Wreck dive site. A baited fishing line about 60 meters deep with a barbless hook at the end was used to catch the sharks. Both the captured tiger sharks measured more than three meters long and each are estimated to weigh more than 340 kilograms (www.FishBase.org).
Dr. Alessandro Ponzo from LAMAVE – Philippines embedded an acoustic tag in one of the tiger sharks. This type of tag will send ‘pings’ to three acoustic receivers strategically moored in different spots around the park once the tagged individual comes within a 500 to 800-meter radius. A fin-mount tag was installed on the dorsal fin of the second tiger shark. While the acoustic tag works only within the park, the fin-mount tag will send signals to a nearby satellite once the tagged tiger shark surfaces anywhere in the world. Both of the tags are expected to produce information on the location and movement of the sharks. These information will be useful in understanding the dynamics of how the sharks use Tubbataha as a habitat, their range, and the potential areas of concern in the protection of the species.
After embedding the tags, tissue samples were collected from the pelvic fin of the sharks. These will be used for genetic connectivity studies in order to contribute to an ongoing global research on sharks. Visible parasites were also removed and collected. The sharks were measured and their gender verified before being released from the hook and ropes which secured them beside the patrol boat. These were carried out on a time span of between 15 to 25 minutes, depending on the size and behavior of the shark. Aside from the two tiger sharks, five grey reef sharks (Carcharhinus amblyrhynchos) were also hooked and embedded with acoustic tags. All of the sharks showed normal activity after release as great efforts were made to reduce the stress of the animals during the procedure.
The team also carried out Underwater Visual Surveys (UVS) for elasmobranchs. Last year’s UVS revealed that Tubbataha has the highest density of whitetip reef and grey reef sharks in the world. Sharks and other apex predators are vital to functional marine food webs and to the health of the marine environment in general. By maintaining the normal abundance of species below their trophic level, sharks facilitate balanced competition between lower groups, therefore improving the species diversity within an area. The research team cruised the Sulu Sea onboard WWF’s research vessel, M/Y Navorca. The crew of M/Y Navorca were most helpful in ensuring the success of the study.
A hooked silky shark being slowly pulled to the surface. ©Phil Dearden/LAMAVE.
Shark tagging team members prepare at their respective stations as the shark gets near the surface. ©Sally Snow/LAMAVE.
When brought to the surface, the sharks were turned upside-down to induce tonic immobility with the head and gills completely submerged underwater. ©Sally Snow/LAMAVE.
Once the shark is in tonic immobility, one of these tags will be embedded in its body cavity through a small incision on its belly. Sharks heal at least twice as fast as humans. ©Sally Snow/LAMAVE.
A grey reef shark is being prepared for the procedure. The mouth and gills of the shark are submerged underwater and the boat slowly moving to allow water to circulate through the shark’s gills. ©Sally Snow/LAMAVE.
Dr. Ale applies suture after installing an acoustic tag on this grey reef shark. ©Sally Snow/LAMAVE.
The team measures the total body length of the shark before release. ©Sally Snow/LAMAVE.
A shark swims away after the operation. ©Sally Snow/LAMAVE.
LAMAVE shark researcher and adopted Marine Park Ranger Ryan Murray holds a new hook on his left hand. On his right is a hook after being disfigured by the ‘big one that got away’. ©Sally Snow/LAMAVE.