Thresher Shark: A rare encounter

A visitor to the Seychelles recently shared a photo of a “strange-looking” marine species he had caught on a fishing trip close to Praslin. They could tell that this was no ordinary fish but rather a very peculiar-looking shark with its unusually rounded face and conical snout and a long, curvy whip-like tail almost double the length of its body. This individual was quickly recognised as the iconic Thresher shark or, more specifically, the Pelagic Thresher (Alopias pelagicus), also commonly known as “Renar” in Creole.

What the visitor and his fellow fishermen did not know was that they had caught a rare specimen of an endangered species that was once on the brink of extinction. Luckily for conservation, fearing that this was a rare species, the fishermen safely released the shark. The video of the shark being released and the photos are now photographic evidence that this species frequents the Inner Islands, providing a spark of hope for the species and the health of the ecosystems.

The Pelagic Thresher is the only one of the three species that frequent the Indian Ocean and the Pacific Ocean. The two other species, the Common Threshers (Alopias vulpinus) and the Bigeye thresher (Alopias superciliosus), are listed as ‘Vulnerable’ by the International Union for Conservation of Nature (IUCN) and are found globally. All three species are naturally docile and are, therefore, highly susceptible to being captured by humans at various scales, leading to drastic declines in their worldwide population. These listings are also based on the fact that Thresher sharks take at least 12 to 13 years to reach maturity and will have only one to two pups per breeding cycle. As solitary creatures, once they reach maturity, Threshers travel to small pockets of the world ocean, leading to reduced genetic diversity, putting the species at risk of population collapse and possible extinction.

What’s more interesting about this species is that it uses its tail fin to jump out of water, possibly as a form of communication –similar to dolphins. Recent videos have also proven an old anecdote that the long tail is used to stun its prey through a wiping or lashing movement that can kill small fish such as mackerel. Other species, such as Humpback whales and Sperm Whales, also exhibit similar fishing tactics. Imagine the strength of a fish that can grow to 4.6 meters (and even 6 meters as an adult) and at a size of more than 290 kilograms to be able to leap out of water. Beyond their agility and manoeuvering ability, Threshers are shy and non-aggressive, thus typically posing no danger to humans.
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This encounter is just another example of how vast the ocean is and truly little we do not know about the marine life that inhabits it. Only recently did a video captured a Thresher shark giving birth, but their preferred habitat, feeding habits, etc., are yet to be documented. This has not prevented the Thresher shark from being the target of sports and commercial fishing, where its fins and meat are considered a delicacy. With 37% of sharks currently being threatened with extinction, there is so much we would lose if this shark had not been released, like the inevitable fate of many others. Plus, we are now more intrigued to encounter this species in its habitat and why not enjoy the absolute awe of a such a marine creature?