Shark repellent


 * ''For the business strategy see Poison pill.

A shark repellent is any method of driving sharks away from an area, object, person, or animal. Shark repellents are one category of animal repellents.

Overview
Shark repellents have been of interest to human beings for many years, for a number of reasons. Food fish caught by fishermen are also prey of many sharks, and a net filled with such fish can be very attractive to sharks in the area. Sharks themselves are sometimes caught inadvertently by fishermen. Sharks sometimes bite expensive underwater equipment such as cables, damaging or destroying it. Finally, shark repellents can be used to protect sharks by driving them away from areas where they are likely to be killed by human beings; in this case, the shark repellent serves as a conservation method.

For all of these reasons, shark repellents have attracted interest for as long as people and sharks have been encountering each other.

History
Some of the earliest serious 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, both real and imagined. 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 principles in dead shark bodies that repelled other sharks. Eventually, it was determined that certain copper compounds, such as copper sulfate and copper acetate, in combination with other ingredients, could mimic a dead shark and drive live sharks away from human beings in the water. For years, a combination of copper acetate and dye was supplied to sailors as a shark repellent.

Unfortunately, subsequent research revealed that the protection offered by these compounds was mostly an illusion. There were not nearly as effective as they had been made out to be.

Today, the search for an ideal shark repellent is still ongoing. Some research, based on seriochemicals, looks promising. Electrical devices that disturb a shark's delicate lateral line system also seem to be at least partially effective. But the goal of the perfect shark repellent still remains elusive.