Sharks are fitted with acoustic tags, which emit a sequence of low frequency "clicks" that give each tag a specific audible ID number. These unique signals can be detected and recorded by special receivers.Sharks have to be 400-500 meter from one of the receivers to be recorded.
Sharks can be tagged externally, meaning on a fin, a method that allows tagged sharks to be tracked for a short period of time. Or the tag can be internal, meaning the tag is implanted into the sharks belly through a roughly 2 inch incision, these tags last for up to 10 years and are more suitable for long term studies, especially of shark movements around an island group as Palau.
To capture a shark a single baited hook is suspended from a large, anchored buoy that is monitored continuously. After some initial commotion, a captured shark will soon quieten down enough to be brought alongside the boat.
When safe to do so, experienced research staff secure the shark with suspension ropes and carefully roll the shark onto its back, putting it into a sleep-like state known as ‘tonic immobility’. A small incision is then made in the shark’s abdomen, the tag inserted into the body cavity and the incision closed with a few stitches. At the completion of the minor surgery the shark is rolled over to wake it up.
Even though the process only takes a few minutes, great care is taken to keep the shark’s head and gills in the water so that it can continue to breathe during the procedure. A plastic ID tag is attached to the dorsal fin as a visual record that the shark has been internally tagged. Details about the shark are recorded such as species, sex, length and a genetic sample is taken. Once the tagging process is complete, lines are carefully removed and the shark is released.
Micronesian Shark Foundation's shark tagging program includes tagging of sharks with acoustic and satellite tags, deploying acoustic loggers around Palau’s reefs, collecting measurements and DNA samples from tagged sharks.
In coordination with the Attorney General's office of the Republic of Palau, further information is obtained through DNA samples from confiscated shark fins.