The Tri-Service and civilian team of divers studying sharks off the coast of Costa Rica that we mentioned in the story - Divers go to depths of Pacific to tag sharks on July 7 - have now completed the most successful Hammerhead tagging expedition ever.
Petty Offficer Steve Paris-Hunter tagging the Hammerhead sharks . Opens in a new window.

Petty Offficer Steve Paris-Hunter tagging the Hammerhead sharks

The team were deployed to Cocos Island to tag sharks in association with the Shark Research Institute (SRI) and Costa Rican conservationists.

The expedition, dubbed ‘Jurassic Shark', was set up to investigate the migratory routes of Hammerhead sharks, to help prevent the illegal practice of poaching them for their expensive fins. The team's success surpassed any expedition of its kind, and they tagged 15 sharks.

The team were also able to make a practical difference to the conservation of sharks when an illegal fishing boat was found dangerously close to one of the biggest known population of Hammerheads in the world. Somewhat upset by this they approached the boat and photographed it together with the island as a backdrop. The boat was then reported to the National Park headquarters on the island and will now be prosecuted.

Major Andy Reid, Jurassic Shark team leader said: "Few people realise that if we want to see sharks at places like Cocos Island in the future we must know where they are and protect those areas too. Baby Hammerheads have never been seen at Cocos Island, which means they are breeding somewhere completely unprotected. This work will help to identify migratory corridors and other areas in need of special protection. Overall Hammerhead numbers at Cocos are thought to have already declined by 71% but we still need scientific evidence in order to get anything done about it.”

"Being close enough to a Hammerhead to tag one (about a metre away) does not result in the slightest feeling of fear - only a mixture of admiration combined with incredulity that anyone would want to harm such a fantastic creature in order to produce nothing more than a bowl of rather tasteless shark fin soup!”

Stormy Weather near Cocos Island

The sharks spent the night feeding in deep water and then came up to natural cleaning stations during the day in order to have their parasites removed by small fish occupying the cleaning stations.. The divers waited for the Hammerheads to swim into a cleaning station and moved in slowly, as close as possible, to tag them using a spear gun.

The sharks swim much more slowly or while waiting to be cleaned and reacted to being tagged with a surprising degree of lethargy. On one occasion however, a young female did react by snapping the spear tip. The team later came across the same shark and were amazed to see that the tag had gone straight through her body. Fortunately, she seemed to be totally happy with no ill effects. On another occasion the rest of the sharks seemed to take exception to one of their number being tagged and Sgt Gareth Thomas from the Royal Marines found himself fending them off with his spear gun!

Of the 15 sharks tagged, 10 now have radio tags and 5 have satellite tags. The satellite tags are designed to read the temperature, depth and approximate location experienced by the shark every 1 to 6 minutes for periods up to 120 days. They then release themselves from the shark and download this information to a satellite. The five sharks satellite tagged on the expedition are the only active satellite tags on Hammerhead Sharks in the world. These will ultimately give an indication of where they go to feed and breed. This information is vital as the sharks almost certainly leave the twelve mile protection zone of the Cocos Island national park. The tags and receivers in all have a combined value in the region of £16,000.

Diving conditions varied from benign to extremely challenging as the requirements of the project meant that the team had to dive some of the more seaward sites in bad weather, with waves reaching in excess of two metres high. This resulted in strong currents and difficult surface conditions.

The military team greatly enjoyed working with the civilian scientists and were impressed by their tireless passion for their work. And the fact that this was the most successful Hammerhead tagging expedition ever was a direct result of the teamwork, ingenuity and, of course, weapon handling skills. Hammerheads are notoriously nervous, skittish animals and tagging them whilst being pushed around by a current or swell is not necessarily something anyone can do, that is assuming you can even persuade them to get in the water!