A shark-proof cage is a metal cage used by an underwater diver to observe dangerous types of sharks up close in relative safety. This can include various species of shark, but the most commonly observed within the confines of a cage are the great white shark and the bull shark, which are both known to be aggressive at times. Shark-proof cages are built to withstand being rammed and bitten by sharks, and are intended to protect the user from potential injury. Cages can provide a visual and tactile deterrent to sharks. Cage-diving allows people to closely monitor sharks for scientific, commercial or recreational purposes, and sometimes interact with them.
The shark-proof cage is also used in the controversial exercise of shark baiting, where tourists are lowered in a cage while the tour guides bait the water to attract sharks or stimulate certain behavior.
Video Shark-proof cage
Early development
Shark cages were first developed by Jacques Cousteau. Cousteau used a shark cage during the production of The Silent World which was released in 1956. Rodney Fox developed his own shark cage in the 1960s. Fox's first design was inspired by a visit to a zoo he made after surviving a near-fatal shark attack in 1963. Later designs were refined further and put to use by documentary filmmakers and abalone fishers who sought personal protection from great white sharks. James Gimbel was one filmmaker involved in the design of a shark-proof cage which was used during the production of Blue water, white death (1971).
Self propelled version
On September 4, 1979, US patent number 4166462 was issued for a self-propelled shark-proof cage; being designed to allow abalone divers to collect abalone without becoming vulnerable to attack. Thanks to the propulsion system, abalone divers would exert themselves less and, therefore, be able to collect their prey for longer periods of time. The patent abstract details a self-propelled cage with at least one access opening and a propeller mounting frame that carries both an air motor and a propeller. Buoyant material is attached to the frame so that the cage may be made neutrally buoyant in saltwater. This patent expired on September 4, 1996.
Shark cage diving tourism
During the 2000s, shark cage diving become increasingly popular as a tourist activity. In South Australia, tourists are taken by boat from Port Lincoln to the Neptune Islands in southern Spencer Gulf where they view great white sharks either from a cage tethered to the back of a boat near the surface, or from a cage lowered to the seabed. The government considers the activity to be one of South Australia's "iconic nature-based tourism experiences" which supports 70 jobs and contributes over $11 million to the state's economy.
Maps Shark-proof cage
Shark baiting controversy
In South Australia, abalone divers have been attacked by great white sharks, and divers believe that great white shark cage diving tourism has altered shark behavior including making them more inclined to approach boats. At least one abalone diver, Peter Stephenson has called for a ban on shark-cage diving and described it as a "major workplace safety issue". The government of South Australia claims that there is "no scientific evidence" to suggest that the general public is at elevated risk of shark attack as a result of shark cage tourism.
Opponents of the cage-diving industry, such as shark-attack survivor Craig Bovim, believe that the constant shark-baiting used to lure sharks to tourists' cages may alter sharks' behaviour. Bovim's opponents, such as marine environmentalist Wilfred Chivell, contend that there is no correlation between shark-baiting and shark attacks against humans. However, there is evidence that the baiting of sharks for tourism does alter the patterns of movement of Great White Sharks.
Shark cage accidents
In 2005, a British tourist, Mark Currie, was exposed to a high risk of injury or death when a 5-metre (18 ft) great white shark bit through the bars of a shark cage being used during a recreational shark dive off the coast of South Africa. The shark circled the boat several times, and began to attack the side of the cage, then started to crush and bite through. The captain of the boat was trying to distract the shark by hitting it on the head with an iron pole, but the shark bit into one of the buoys at the top of the cage, which made the cage start to sink. Currie realized that he could either get eaten or drown because he had only a mask, not any breathing apparatus. Currie quickly swam out of the top of the cage and was pulled to safety by the boat's captain, who fended off the shark with blows to its head.
In 2007, a commercial shark cage was destroyed off the coast of Guadalupe Island after a 4.6-metre (15 ft) great white shark became entangled in it and tore the cage apart in a frantic effort to free itself. Tourists captured video of the incident, which quickly spread throughout the Internet.
See also
- Protective Oceanic Device
- Shark net
References
Source of article : Wikipedia
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