Shark repellent

A shark repellent is any method of driving sharks away from an area. Shark repellents are a category of animal repellents. Shark repellent technologies include magnetic shark repellent, electropositive shark repellents, electrical repellents, and semiochemicals.

Shark repellents can be used to protect people from sharks by driving the sharks away from areas where they are likely to kill human beings. In other applications, they can be used to keep sharks away from areas they may be a danger to themselves due to human activity. In this case, the shark repellent serves as a shark conservation method.

There is evidence that surfactants such as sodium lauryl sulfate can act as a shark repellent at concentrations on the order of 100 parts per million. However, this does not meet the desired "cloud" deterrence level of 0.1 parts per million.

Research indicates that sharks will avoid an area when they smell chemical released by dead and dying sharks. Six chemicals were synthesized from shark glands and tissues and used in experiments. Sharks immediately reacted once they detected these chemicals. To quote a 2004 Associated Press article, "Fisherman and scientists have long noted sharks stay away if they smell a dead shark." This effect was dramatically demonstrated in a MythBusters episode in which Adam Savage and Jamie Hyneman were able to drive away 10-20 Caribbean reef sharks and nurse sharks in only a few seconds on two separate occasions. The repellent used consisted of extracts from other species of shark bodies, and sharks did not return for over 5 minutes on both occasions.

Some of the earliest research on shark repellents took place during the Second World War when military services sought to minimize the risk to stranded aviators and sailors in the water. Studies at the time, combined with historical research, revealed that about the only thing that will drive sharks away is the odor of another dead shark. Efforts were made to isolate the active components in dead shark bodies that repelled other sharks. Eventually, it was determined that certain copper compounds like copper acetate, in combination with other ingredients, could mimic a dead shark and drive live sharks away from human beings in the water.

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