A porbeagle swims away carrying the first satellite tag to be deployed on these sharks in UK waters.
Cage-diving with porbeagle sharks off Cornwall is quite a challenge - but it can be done, declares Richard Peirce, following a revealing expedition this summer
ON 9 MARCH, 1993, angler Chris Bennett caught a porbeagle shark weighing 229kg, which is the world record. I wonder how many divers realise that sharing British seas with them is a 36-stone first cousin of the great white! Bennett caught his shark 400m off the cliffs at Dunnett Head in the Pentland Firth. There is no record of a shark this size being caught off Cornwall but 135-180kg sharks are common both close in behind the surf line and on wrecks and reefs. Porbeagle sharks are skittish, nervous and avoid humans, so divers will be very lucky to see one. Through my Shark Cornwall cage-diving project I hoped to achieve a world first by finding a way to get into the water with them. So this July I, along with seven volunteers, ran the first porbeagle-specific shark expedition off North Cornwall. We were aiming for a whole series of breakthroughs. We wanted to be the first to deploy satellite tags on porbeagles on this side of the Atlantic; to achieve the first decent-quality underwater footage plus reasonable still images of these sharks; and to observe them on the surface and work out how to get cage-divers in the water with them. This summer's unsettled weather was well-established by the time of the expedition, so we were lucky to lose only one the six days planned at sea. Four of the five satellite tags were supplied by Nick Pade, a student from Aberdeen University doing his PhD on porbeagle sharks, and I provided the fifth. Costing more than ?1500 each, the tags had to be handled with care - and we needed to be sure that, once deployed, they would stay on the shark.
THE PRECISE LOCATIONS we were working were kept secret, because these sharks are a very easy target for commercial longline fishing. The last thing we wanted was to provide a map to guide fishermen to kill them. Our fears were well-founded. The week after our expedition finished, we received reports of a longliner, working only a few miles away around Lundy, catching and killing over 60 sharks. During our five days working with the sharks we observed a sex mix biased towards females, which probably represented 70% of the animals we encountered. The catching of 60 of these critically endangered sharks, mostly female, will have had a devastating effect on that local population. I knew that obtaining underwater images, both still and moving, would be difficult, because porbeagles are nervous around humans. Twice before porbeagles had been around my RIB after chumming and I had tried to slip into the water to get shots. On one occasion I dropped in on the opposite side to where the shark was, and by the time I had sneaked round the back of the boat, it was long gone. The other time I had repeated the tactic but with only slightly more success. I saw the shark do a fast crossing pass in the distance, angling towards me, but it jinked away just as I was thinking a shot might be possible. Those of you who have dived with white or blue sharks in chummed situations will know that they often appear almost lazy or laid-back as they make their passes at the cage. But there's nothing lazy or laid back about porbeagles. They're like Ferraris that have overdosed on speed. I knew that the best chance of getting images lay in remote methods. Once we had footage and images we could then experiment with getting into the water with the sharks. Simon Spear was the expedition's videographer. Using a polecam, and assisted by Mike Sharland and David Green with a back-up camera, he obtained good footage on day one! We had five different sharks around our boat, and it could easily have been double that number. As soon as we had a shark in our chummed area it would find the bait tube. We would try and work it towards the boat by drawing in the tube and getting it close enough to the polecam. We grabbed still images from the movie footage obtained. I had assumed that the satellite tagging would be relatively easy if we found large enough sharks. We had planned to catch sharks for tagging at the start of the expedition before moving on to the more difficult photography. As it was, the difficult part had been achieved first. I was delighted that we could now play for the rest of the week!
OVER THE NEXT FOUR DAYS we deployed four out of five of our satellite tags, which are set to pop off the shark after a certain time, floating to the surface and transmitting data gathered. We deployed one set for 30, two for 60 and three for 90 days. At the end of these periods, we'd know where the sharks had been. The sharks needed to be big enough to take the tags but not so big that getting them onboard would endanger sharks or humans - sometimes a tricky call. As well as tagging we collected fin-tips for DNA analysis and comparison with porbeagles in the USA. We had to catch the sharks on rod and line, but did all we could to minimise their discomfort, and all swam away apparently none the worse. At the time of writing the tags have just started popping off the sharks. In the second week of August we received reports that the longliner that had caught the 60 sharks around Lundy was now catching sharks where we had been tagging them. At that point we became concerned that the population we had discovered would be depleted, and the tag deployments curtailed. During the video/photo part of the week I had an excellent opportunity to study the sharks free-swimming near the boat, and to work out how to approach cage-diving with them. It's a problem well worth cracking, because these sharks would be really exciting to view under water. They are so wary of us that any potential danger to us seemed offset by the challenge of getting them close enough for a good look or a shot. They are also really reactive to chum. At one time I thought they were darting in and buzzing the pole camera, before I realised that it was in the water right beside the chum bag. The mirrored bait tube had proved a very successful tool with blue sharks, and so it was with the porbeagles. They never tried to grab it but always checked it out, giving me hope that we could use it to work them up to a cage.
THE PLAN WE EVOLVED meant using a cage, but not so much for the safety of humans as to keep them under control in one place. Snorkellers or divers finning around and blowing bubbles looking for and chasing the sharks would mean - no sharks. If we had the cage over the side from the time of arrival and at the start of chumming, the sharks would approach the boat with the cage as part of the profile. We would have one chum tube 12-15m out, and another clipped on a line floating 2m from the cage, then slip the diver into the cage once the sharks had arrived and got used to the set-up. Let's hope that cage-diving can demonstrably give these sharks a real live value. This will eventually stop instances of overfishing wiping out local populations.
Richard Peirce with the mirrored bait tube.
Porbeagles at the surface, attracted by the bait.
One of the porbeagles, filmed using a pole camera. Looking like smaller great whites, they are distinguished by the white blob at the base of the dorsal fin.
Richard Peirce and the volunteers aboard their boat Mantis.