Sunday, 15 July 2012
No.28 Thresher Love. That is all.
Today I saw my first Pelagic Thresher Shark ALIVE (-much better than the ones I’ve seen lying lifeless in the market). Cutting through the water, with its fox like face and long tail, the sight of it made me smile so much that my regulator slipped out, just for a second….i guess you could say it simply took my breath away ;-) ….
And in truth how could it not? For the thing about threshers sharks is that they are truly wonderful to see in the water…their iconic long tail is unique in the shark world. The upper fork is slim and scythe-like (giving the grim reaper a run for its money) and is nearly equal in length to the animals body. In fact it is possible for a mature thresher shark to reach a length of over 4 meters, 2 of which make up its tail alone.
And so I hear you ask, what do they do with such a fancy tail? Well its long been accepted that the sharks use their tails to herd and whip prey (mainly schooling fish and squid) into terminal submission…or to put it another way, they stun or immobilise the fish so that they are ready for the taking. Video footage obtained in Moalboal, Cebu confirms this and what’s more fisheries reports indicate that 97% of thresher sharks caught on long lines are hooked by the tail, which one could argue is a clear indication that the shark attempts to stun its prey with its caudal fin (tail) before attempting to manipulate it with its mouth.
And that’s not all that makes them special. Those of you that know your sharks, will know that Pelagic Thresher Sharks are usually found deep in the ocean (+150m), for one thing the name is a bit of a give away as the word ‘pelagic’ means ‘of or relating to the open sea’. So what are these cowboys of the ocean doing hanging off Philippine islands, and why is a shark that is supposedly pelagic being seen by divers at less than 30meters?
Now this is where things get a bit special. For while thresher sharks are known to occupy the seas of the indo-pacific as well as further afield in places such as Australia, South Africa, California…the island of Malapascua located at the northern tip of Cebu in the Philippines, is one of the only, if not the only place in the world where one can dive with the Pelagic Thresher Sharks (one of three species of thresher sharks found in the world, the other two being the Bigeye and the Common Thresher). The reason for this is quite simply because of the discovery of cleaning stations less than 30 meters below the surface. A cleaning station is an area where sharks, rays and other fish visit in order to get parasites removed by resident cleaner fish, these fish pick away the parasites that accumulate on the sharks body.
To find a cleaning station so shallow is very rare and much of what is known about Thresher sharks today has come from the study of the population visiting Monad Shoal off the island of Malapascua. Leading the research here is ‘The Thresher Shark Research and Conservation Project’, a conservation project initiated by marine biologist Dr Simon Oliver from the UK, but based out here on Malapascua island. The project is a non-government-organisation (NGO) and is supported almost entirely by volunteers. Without the volunteers there would be no project. It is their commitment to the research, their support and their hard work that makes the data collection possible. Under the guidance of Medel Silvosa, the field operations manager, volunteers place an underwater camera down on the sea floor in order to record the behaviour of the thresher sharks. Since the project began back in 2007, volunteers have helped shed light on the behaviour of Pelagic Thresher Sharks in response to resident cleaner fish, they’ve investigated correlations between parasite presence and injury on Pelagic Thresher Sharks and perhaps in my opinion, most importantly they have helped contribute to the understanding of the impact and effect of dive tourism on the abundance of thresher sharks. This is pretty important, especially when you think how much these sharks have brought to the island of Malapascua – a tourism trade that didn’t exists before the discovery of the cleaning stations. This has changed the life of a fair few islanders, bringing an alternative way of living to some residents of the island, perhaps not all, but definitely a number. The worry however, as with any tourism that relies on the natural world (just think of the Whale Sharks in Donsol), is finding the balance of maintaining the livelihoods created by tourism as well as protecting the animals that make that tourism possible.
One concern people have here is the effect of divers sitting on the sea bed (as they watch the sharks swim by). To some this might not seem like a big deal, but when you realise that each time a diver rests on the sea floor it breaks whatever substrate lies below then things get a little complicated. Of course, sitting directly on corals is the worst- as one can clearly see the often irreversible damage a 10 minute rest can do to these ancient colonies of little animals. But what’s not as obvious is the effect divers have on sitting on patches of the seafloor that they might consider just to be ‘rubble’ – ok so it doesn’t look like much, but this ‘rubble’ is one of the things that coral need in order to colonise…coral needs something to hold onto, sand simply doesn’t cut it. And the more divers that sit on this ‘rubble’ the sooner it turns to sand and then where will the corals colonise? No corals means no resident fish, which then begs the question where will the cleaner fish live? And if there are no cleaner fish, then who will clean the sharks? No one. And where will the sharks go? And there you have it, they’ll all move on to create a different cleaning station somewhere else, maybe 50meters down, too far for us to dive without getting technical: Good bye cleaner fish, goodbye threshers.
But it’s not all doom and gloom. The local dive shops collect 150 pesos from each diver that dives Monad Shoal. 20% of this fee goes to the barangay (village), while the remaining 80% goes to the municipal office who use it to provide a salary and fuel for the bantay dagat (guardians of the sea) and to help install mooring lines at some of the established fish sanctuaries around the island. This is definitely a good thing, but what would be wonderful is to see Monad Shoal become a fish sanctuary or a Marine Protected Area (MPA). If Monad Shoal became an MPA, ordinances could be set up to help protect the cleaning stations-better diving regulations? Designated observation areas? Some restricted areas? The ultimate dream being that it would help sustain the thresher shark tourism here and the community that rely on it….who knows maybe one day….
If you would like to find out more about the Thresher Shark Research and Conservation Project or fancy becoming a volunteer and contributing to the great work it does here on Malapascua, then wonder over to their website:
Video to follow soon…