What is it about sharks, wonders "Whimsy" columnist CLIVE WILLIAMS, who says they have had an undeserved bad reputation since the movie "Jaws"...
I SPEND quite a lot of time swimming in the sea and am aware that Canberra beachgoers seem fascinated by and scared of sharks in equal measure.
As apex predators, sharks play an important role in the health of the marine ecosystem. Fortunately for humans, we are not part of the shark food chain.
Sharks have evolved over more than 420 million years and there are some 500 species. They range in size from the small dwarf lantern shark only 17 centimetres long, to the whale shark, the largest fish in the world, which reaches 12 metres in length.
Sharks have amazing senses:
- They have scent detectors in each nostril that can locate an injured fish from the chemicals in fish intestines.
- Their eyes are specially adapted for hunting in the dark.
- They may be able to hear prey from many kilometres away.
- They have receptors that can detect electromagnetic fields; these help them detect prey and navigate over long distances using the earth’s electromagnetic fields.
- They have a tactile sensory system able to detect water speed and pressure changes. This helps them navigate and detect injured prey.
Sharks have had an undeserved bad reputation since the movie "Jaws", and of course in some circumstances they can be dangerous to humans. Bull sharks are more likely to charge and bite, while Great Whites may tentatively bite a human to see what it is. Clearly an inquisitive bite from a Great White can prove fatal, as was sadly the case on May 18 with a surfer off Tuncurry Beach on the NSW north coast.
However, basic precautions should keep you safe: don’t swim in the sea after dark – or at dusk or dawn; avoid large shoals of fish that might attract sharks; don’t swim or surf where Great Whites migrate or breed; don’t swim where the water is less saline (Bull shark habitat); don’t swim off a boat that’s fishing, and don’t spearfish – because wounded fish attract sharks.
I have been privileged to see a great many sharks over the years, both when swimming on the surface and when scuba diving and have never had a problem with them being aggressive.
I often swim at Manly beach where there is a two-metre, Grey Nurse shark popularly named Bruce living in the marine reserve. Bruce has never shown any interest in the many people that swim over him (or her) every day between Manly and Shelly Beach. Wobbegong sharks are also common there, but they are the labradors of the shark world and would normally only bite if someone pulls their tails. In fact, the last fatal shark attack at Manly was way back in 1936.
In 2005, I went on an organised shark-feeding trip in the Bahamas. We scuba dived to the seabed from a boat and an Esky-sized bait box was roped down to the guide.
Sharks are quite intelligent and, as soon as they saw the bait box, started circling our group in large numbers. The guide gave each of us a stick about 30 centimetres long and stuck a filet of fish on the end. When you held it out, a shark would come and take the fish. Once the bait box was empty and the open box shown to the sharks, they all left. The guide told us that there had only been one incident in 26 years and that was when one excited diver forgot to use the stick.
Sharks clearly have far more to fear from humans than vice versa. Since 1970, global shark populations have plummeted by 90 per cent – mainly due to overfishing for the Chinese shark-fin market.
Australian politicians past and present have a dismal record when it comes to protecting the environment.
Some Australian fish shops still sell shark meat as “flake” despite the International Union for Conservation of Nature in 2019 listing school sharks as critically endangered.
In the face of government inaction, the Australian Marine Conservation Society has urged Australian seafood consumers to take it on themselves to stop buying flake.
Equally concerning is the government’s ongoing failure to prohibit the export of Australian shark-fin products.
Clive Williams is a Canberra columnist
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