Shark Tales

SEMINYAK ~ Nur nuh, nur nuh, nur nuh, nur nuh (can you see the fin yet?)

The terrifying theme from Jaws is the first thing that springs to mind when most of us think of sharks. However, they are far from being the insatiable man-hunting demon of the deep portrayed in this movie (and its various successors – the most ridiculous of which had the shark’s mother hunting the family members down across the Caribbean). Peter Benchley, who wrote the book on which the film was based, spent the subsequent years tirelessly campaigning for the protection of sharks, and raising environmental awareness.

“If I were to try to write Jaws today, I couldn’t do it. Or at least the book I would write would be vastly different and, I surmise, much less successful.

“I see the sea today from a new perspective, not as an antagonist but as an ally, rife less with menace than with mystery and wonder. And I know I am not alone. Scientists, swimmers, scuba divers, snorkellers, and sailors all are learning that the sea is worthy more of respect and protection than of fear and exploitation.

“Today I could not, for instance, portray the shark as a villain, especially not as a mindless omnivore that attacks boats and humans with reckless abandon. No, the shark in an updated Jaws could not be the villain; it would have to be written as the victim, for, worldwide, sharks are much more the oppressed than the oppressors.”

Sharks are indeed consummate predators. They evolved in their modern form over 100 million years ago, and very little has changed since. Everything about the shark, is perfectly designed for its purpose. The oldest fossil records of the Great White shark date from about 60 million years ago.

The shark is a fish with a skeleton made of cartilage (think the bendy bit at the end of your nose), which allows suppleness and movement through the water. They do not have swim bladders like most fish, but rather manage their buoyancy using a substance called squalene, stored in their livers. They breathe, like all fish, by extracting oxygen from water through the gills. Some species of shark have lost the ability to pump water over their gills when they are resting; these species must spend their lives in constant motion – if they stop, they die.

The waters around Bali do not abound in sharks – possibly due to fishing. What we do have are smaller sharks, and observing them is a great introduction to this incredible fish. The shark most commonly seen by divers around Bali is the White-tip Reef Shark, though those seeking an encounter with a bigger shark might also be lucky enough to see Hammerheads (very rare), or even the incredible Whale Shark.

All sharks hunt using three specially refined senses. Their sense of smell is acute, and some species are able to detect blood in as low concentrations as one part per million. Their hearing is equally well developed, with a special “lateral line” that attunes them to minute vibrations in the water. They also use “electoreception.” Electrical currents in the water are detected using special receptors, known by the unlikely name of Ampullae of Lorenzini. Different species of shark have different numbers of these, and correspondingly, greater or lesser sensitivity to the electrical fields produced by all prey.

The White-tip Reef Shark (Triaenodon obesus) is a completely different species from the Oceanic White-tip (Carcharhinus longimanus), and an entirely different kettle of fish. It has been seen as deep as 120 meters, though it is normally found in shallow coral reefs. They feed on fish, octopus and crustaceans. This species of shark is generally more active at night, and during the day can be frequently observe “sleeping” on the bottom of the ocean. It is not aggressive, and when disturbed normal behaviour is to flee, though, like all animals, it may bite if harassed. They bear live young – with one to five pups per litter. This small litter size, and their specific adaptation to coral reefs – a habitat that is constantly under threat – mean that the White-tip reef shark, once commonly seen in tropical waters around the globe, is already classified as “near-threatened” by the The World Conservation Union. White-tips are small sharks, reaching maturity at only 100 centimeters.

Hammerheads have been observed in the deeper, more turbulent waters off the east and north coasts. This is undoubtedly the weirdest species of shark, and surprisingly, the most modern. The eyes and nostrils of the shark are located at the end of the protrusions from the side of the head. This allows the Ampullae of Lorenzini and the nasal receptors to be more widely spaced, allowing greater sensitivity and accuracy when tracking prey. The Hammerhead is the only shark known to have demonstrated asexual reproduction. A female shark in a US zoo in 2001 was gave birth to pups, though she had had no access to a male for over three years. Subsequent DNA testing proved that in truth, the pups had no paternal DNA. This survival ability has never before been documented in any shark species.

Sightings of Whale Sharks in Balinese waters are few and far between, but there is no disputing they are here (August 30 on the USAT Liberty wreck at Tulamben), and an encounter with this majestic creature is at the top of most people’s wishlist. The Whale Shark (Rhincodon typus) is thought to have evolved about 60 million years ago. Despite its massive size – reported to grow up to 20 meters (though the largest reliable report puts the size at 13 meters) – it is truly harmless. It is a filter feeder: it feeds by swimming along with its mouth open and ingesting plankton, krill and other tiny oceanic life. Despite their intimidating size, they have been reported interacting with divers, and appearing to enjoy their attentions. In Bali’s seas, one is most likely to see juveniles, and these creatures display great curiosity towards divers.

So a quick introduction to just a few of the species of shark that you might be lucky enough to see while diving in Bali: the small, the weird and the huge. Next time you are diving on the wreck at Tulamben, occasionally glance out into the blue – you never know what might be peering back at you.

The writer is sales manager at AquaMarine Diving – Bali.

Filed under: The Island

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