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Ignorance is Bliss, Better Not to Know as Sharks Cruise by Unnoticed

Updated on November 16, 2016
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John uses his scientific (PhD) & research skills to review & home building & interior design, renovation. John built his straw bale house.

Sometimes it is better not to know. When my family lived near Byron Bay some of the locals became concerned about the healthy risks of tank water. All sorts of things from bird dropping, frogs, insects as other stuff can get into the water from the roof. There are mesh filters but the tiny stuff gets into the tanks. My wife suggested that we should have the tank water tested. I said: "No way - do we really want to know?". Besides we couldn't afford it and what would you test for?

But the main argument was that if you drink tap water the biological organisms in your gut get used to it and there is hardly ever any problem. Unless of course a frog dies in the tank or the tank may get infected by Giardia Lamblia, a parasite, perhaps derived from bat droppings. Giardias causes diarrhea and is spread by contaminated drinking water. It is better not to know.

Another example of this arose from tracking studies conducted to monitor the movement of Bull Sharks in Sydney Harbor and up the coast of Northern NSW, Australia.

For many years these fearsome looking sharks have been blamed for rare shark attacks in murky canals, inlets and river estuaries at the Gold Coast and in Sydney Harbor.

That the Bull Shark was responsible was never proven, it was merely presumed to have caused the attacks as these are the largest sharks that venture into the rivers, bays and estuaries.

The bull shark has a fearsome reputation
The bull shark has a fearsome reputation | Source
Tagged sharks showed that they cruised through popular swimming areas without being noticed. No shark attacks despite their occurrence in many popular swimming areas
Tagged sharks showed that they cruised through popular swimming areas without being noticed. No shark attacks despite their occurrence in many popular swimming areas | Source
The risks of shark attacks are over rated compared with driving a motor vehicle.
The risks of shark attacks are over rated compared with driving a motor vehicle. | Source

Shark Movement Patterns in Bays, Inlets and Estuaries

Studies on the Gold Coast and in Sydney have involved capturing the sharks and inserting acoustic tags into the abdomen of the sharks. These tags emit a unique sound signal that can be picked up by hydrophones. This means that the movements of individual sharks can be tracked through the murky waters of canals on the Gold Coast and in the nearby Nerang River.

One large and fearsome bull shark roamed about the canals during the week and would often find a deep hole in the river in which it would stay for the weekend. Often these weekend get-a-way spots coincided with areas that were very busy with human activity. This included swimmers, sailors, water skiers, fishing and many boating activities. These disturbances appear to have no effect on the shark and while close-by the shark n ever many any attempts to get close to people or attack them. This does not mean that they are not dangerous, nor that people should not take the usual precautions. But ignorance was bliss. The people did not know there was a large bull shark in the ares they used for recreation and it did not matter.

The researchers said that Bull sharks were 'quite smart', but were not aggressive to humans. They suggested that it was more likely that any attack on humans occurred because the shark was bumped by a swimmer in very murky water and the shark thinking it was mullet or other fish they were hunting. Dusk, dawn and at night were the main time when bull; sharks were active. Large rainfall events may push the sharks into the canal areas. Also appeared that the way the Nerang River is managed made the Nerang River less suitable for the sharks.

The other finding that there were a lot more of these sharks in the canals, than was first thought, perhaps up to 100. Despite this shark attacks in this area are extremely rare, but they have occurred. Ignorance is bliss.

The other point is than many people won't go swimming at the beach because they are afraid of the sharks. Yet they will happily drive down to the beach and sit on the sand. The risk of them being injured or killed on the road getting to the beach is probably 1,000,000 time greater that being the victim of a shark attack. But it does not stop them driving.

A similar tagging program has been conducted in Sydney Harbor, down south. Over 100 bull sharks have been tagged and tracked. Very few other sharks were ever caught in the harbor Some of the bull sharks were quite large, up to 2.2 to 3.3 metres long.

The other interesting finding was that the sharks were not permanent residents. Most of the sharks arrived in late November or early December, stayed through the summer months and left in mid to late April. The average time spent in the harbor was about 17 days and the visits ranged in length from 1-21 days.

The sharks moved all around the harbor from shallow to deep water. The sharks appear to have a regular annual migration, going north in winter and returning each summer. Of the 11 Bull sharks tagged in 2009-2010 seasons, nine returned during the summer and autumn of 2011.

The major surprise was that there were quite large numbers of these large sharks moving around the area, including many of the recreational areas. People did not know they were there, and sharks and people coexisted happily for hundreds of years - Ignorance in Bliss.

One sharks tagged in Sydney harbor swam more than 5000 m north from Sydney to Townsville ( Tropical North Queensland) and back.

Many of the sharks that cruise quietly and secretly in Sydney Harbor could well be same ones that cruise around the Gold Coast canals and coastal waterways of Queensland.

Another shark tagged at South West Rocks in Northern NSW on 24 January 2010, was located then located near Townsville on 10 December of the same year and Lady Elliot Island off the coast in the Great Barrier Reef waters on 23 December 2010.

Ignorance is Bliss. The results of the tagging study have triggered calls for the sharks to be eliminated from Sydney Harbour to protect swimmers from the risk of shark attack. Before the study no one know they were there and no one worried about them.

Common Sense Precautions to Avoid Shark Attacks

Shark attacks are extremely rare and swimmers are urged to take common sense precautions.

These include:

  • Don't swimming at dawn or dusk or in the middle of the night
  • Avoid swimming by yourself
  • Avoid swimming when there are large schools of fish in the area that sharks may be hunting
  • Avoid swimming in murky water

Do you worry about sharks when swimming in bays and inlets?

See results

© 2013 Dr. John Anderson

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