Biology Online is a Biology blog and dictionary site that provides up to date articles on the latest developments in biological science. The Biology Online Dictionary is a completely free and open dictionary with over 60,000 biology terms. It uses the wiki concept, so that anyone can make a contribution.

Passionate about Thresher Sharks in the Philippines

My work as a marine biologist has drawn me to the Coral Triangle, an area of our oceans consisting of the highest levels of marine biodiversity. You can imagine that the abundance of marine life led to a high reliance of local populations on seafood. It is a cruel irony that some of the methods used to harvest this seafood destroy the very foundations of seafood supply. So when I decided to hop on the Conservation bandwagon, the Coral Triangle was an obvious choice.

Having decided to pursue Conservation work, specifically in the Philippines, I realised I needed to beef up some of my skills in that area. I came across a conservation project on a small island off the north of Cebu, Malapascua, that worked with the Pelagic Thresher Shark (Alopias pelagicus). Most marine biologists hold sharks very close to their hearts, and the Thresher Shark, with its big eyes and characteristic tail is usually elusive and deep dwelling. The odds of seeing one by chance on a regular dive are pretty much nil. My heart was set, and I got through the application process and proceeded to spend two glorious months diving and studying these magnificent sharks.

One of the important things to remember about working on an upstanding Conservation project is that your work is not glamorous; you don’t do it to get the glory photo of you with [insert your dream animal here]. If you’re doing research you do the dirt work, the essential data collection, that adds to the bigger picture and contributes to data that can be used to lobby for the protection of the [dream animal].

Research Divers - Steve DeNeef
Photo credit: Steve De Neef

The reason you can see Thresher Sharks in Malapascua is the presence of an underwater seamount, surrounded by deep dark waters, that houses coral reefs that in turn are the habitat for several reef fish that provide cleaning services to large, parasite ridden fish. The Threshers, along with the occasional Grey Reef Shark and Manta Ray rise from the depths to visit the seamount to rid themselves of parasites. Cleaner wrasse and Moon wrasse swim in their cleaning stations, salons if you will, until one of these elasmobranchs enters and displays a specific behaviour. The Thresher Shark circles lazily, round and round whilst the wrasses dart up and bite off the parasites. The Grey Reef shark shakes it’s tail feather across the cleaning territory to show the wrasse it’s not about to eat them. The Manta, maybe the most graceful of all sea creatures, hovers above the cleaning station, flicking its wings ever so slightly to stay in place.

Photo credit: Steve De Neef
Photo credit: Steve De Neef

There is a substantial diving industry built around the presence of these animals. Up at the crack of dawn, divers head out and descend on the shoal to catch a glimpse of the sharks, and if they are extremely lucky, a Manta. Whilst there have been several policies implemented to prevent divers from impacting the sharks whilst they clean, you can imagine that a wall of bubbles from a row of divers might be a turn off. In addition, inexperienced divers cannot control their buoyancy and hover for the whole dive, and end up kneeling on the reef to stay put. This has resulted in damaged corals, and in some places, the reef has been reduced to rubble or even sand.

The presence of the diving industry no doubt brings the plight of the Thresher Shark to a global audience. It raises awareness, breeds emotional connection and encourages a passion for the sharks and their environment in a way that nothing else can. But there should always be a balance, the act of raising awareness should not significantly damage the animal or its habitat. Otherwise what’s the point!

Photo credit: Steve De Neef
Photo credit: Steve De Neef

The conservation project aims to study the natural cleaning behaviours and the impacts of divers on the reef and cleaning behaviour. The extent of the disturbance is unknown, and successful managing strategies should be based on robust scientific data. The project aims to find out. Everyday we deployed a video camera to monitor the shark’s behaviour remotely. When the divers left after dawn, we’d do surveys on diver-visited and control reefs. We would spend hours at sea, on the boat during surface intervals. The aim was never to seek out the sharks ourselves. It’s not exactly good science if you are affecting your own results! Volunteering for research projects like this one can give you a wealth of experience, and peek into the industry you want to join. My advice would be to choose projects that will give you certain skills that are useful for your career path, and when you start, to treat it like a job, not a bona fide holiday. You never know if they’ll offer you a job in the end, or if their reference will be critical in the next stage of your career!

For more information please see The Thresher Shark Research & Conservation Project

By Guest Blogger Samantha Craven from Mad As A Marine Biologist

Photo courtesy of Steve De Neef . See more photos at

One response to “Passionate about Thresher Sharks in the Philippines

Leave a Reply

Your email address will not be published.