Shutterstock/nicolasvoisin44/WWF
Shutterstock/nicolasvoisin44/WWF
A large thresher shark in Philippine waters

Battle to save the threshers

Added to Blogs on 22 July 2016
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I saw my first thresher shark back in 2013, 30 metres below the surface of the Visayan Sea, as night turned to day above.

 

An hour earlier my now wife and I had boarded an outrigger in the dark with other excited divers on the sleepy island of Malapascua in the central Philippines, and headed off under the stars toward Monad Shoal. This large, rocky reef is famous as the only site in the world where thresher sharks can been seen daily at recreational diving depths.

Here pelagic threshers routinely rise from the murky depths just after dawn, attended to by fishes at cleaning stations along the reef. The sea was cool but our shivers were at least as much in anticipation as we hovered behind one of the cleaning stations, and peered into the grey blue gloom, desperately trying to make out shapes. Suddenly, a muffled retort from our dive master guided our gaze to the right where a three-metre thresher – as distinctive as can be with its long crescent-shaped tail – crossed elegantly in front of us.

It was an unforgettable moment – made all the more poignant by knowing that thresher sharks have declined by more than 70 per cent in almost every area they are found. And are now in urgent need of protection across the globe.

In the next 20 minutes we saw several more threshers, circling sedately to be cleaned, silhouetted above us like aeroplanes, and even passing close over our shoulders, filling the viewfinder as I implored my camera to focus in the low light. My pictures were dreadful, particularly as using a flash is strictly (and rightly) prohibited as it startles the sharks, but we couldn’t have been more ecstatic as we reluctantly headed back to the surface.

Since then I’ve been back to Malapascua twice, most recently just a few months ago. WWF is partnering with the Manta Trust and Project AWARE to produce a guide to sustainable shark and ray tourism, and we’ve used the thresher diving at Malapascua as a successful real life case study.

Pelagic threshers are one of three species of thresher sharks; a family of sharks that normally hunts small fishes at depths of several hundred metres. It had long been believed that thresher sharks hunt fishes using their whip-like tails but this was only confirmed in 2010 when scientists managed to film pelagic threshers hunting sardines. When they slowed the footage, they could see the sharks using powerful sideways and even overhead tail slaps to stun the schooling fish.

Unfortunately, these extraordinary predators are the most endangered of any pelagic shark family. The depths that the pelagic, big-eye and common threshers inhabit are heavily fished, and they are frequently caught by offshore longlines and pelagic gillnet fisheries, some of which are targeting sharks, and some targeting tuna and other species. These fisheries – and others such as those using gill nets around offshore reefs – are largely unregulated and unreported. This was rammed home for me when I visited the port of Karachi in Pakistan a few months ago, and saw pelagic threshers once again. But this time they were lying lifeless on the docks, after being caught in gillnet fisheries with no catch limits.

 Unsustainable fisheries like this coupled with the lack of conservation measures over most of their range and their very low rates of reproduction – a female bigeye thresher, for example, will have fewer than twenty pups in its lifetime – have left these animals in real peril.

But greater efforts are now being made to protect them. As a result of increasing concern about the plight of thresher sharks, Sri Lanka has proposed that all three species be added to Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which would greatly restrict global trade in thresher shark products – limiting it to fisheries where harvesting is sustainable. This is appropriate as the large fins of thresher sharks are typically exported to Asian countries with a taste for shark fin soup, where they fetch a high price.

Sri Lanka’s proposition has proved popular, and to date 22 other countries and the EU have formally lent their support. The final decision on thresher sharks – as well as the silky shark and devil rays, which have also been proposed for Appendix II – will be made at by the 182 parties at the upcoming CITES meeting in South Africa, which starts in September.

WWF and TRAFFIC strongly support all of these proposals, and we’ll be campaigning hard for them to be accepted alongside our partners in the Global Shark and Ray Initiative and others in the coming months. It won’t be easy, as some countries oppose the listing, but we were instrumental in getting other species of sharks and rays listed on CITES in 2013, and will give it our all again.

And hopefully, enough countries will side with us at CITES and with these remarkable sharks and rays – so that the next time I see a thresher, I will know that we’ve taken a significant step toward saving the species.

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Andy Cornish

Leader, WWF and TRAFFIC Shark & Ray Initiative, Sharks: Restoring the Balance, WWF International

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