A shark repellent is any method of driving
shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
s away from an area. Shark repellents are a category of
animal repellent
An animal repellent consists of any object or method made with the intention of keeping animals away from personal items as well as food, plants or yourself. Plants and other living organisms naturally possess a special ability to emit chemical ...
s. Shark repellent technologies include
magnetic shark repellent,
electropositive shark repellents,
electrical repellents, and
semiochemical
A semiochemical, from the Greek wiktionary:σημεῖον, σημεῖον (''semeion''), meaning "signal", is a chemical substance or mixture released by an organism that affects the behaviors of other individuals. Semiochemical communication c ...
s. Shark repellents can be used to protect people from sharks by driving the sharks away from areas where they are likely to harm 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 are some naturally occurring shark repellents; modern artificial shark repellents date to at least the 1940s, with the
United States Navy
The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...
using them in the
Pacific Ocean theater of World War II
The Pacific Ocean theater of World War II was a major theater of the Pacific War, the war between the Allies and the Empire of Japan. It included the U.S. Pacific Ocean Areas (command). which included most of the Pacific Ocean and its isl ...
.
Natural repellents
It has traditionally been believed that sharks are repelled by the smell of a dead shark;
[Researchers tout shark repellent]
2004 Associated Press, "Fisherman and scientists have long noted sharks stay away if they smell a dead shark." however, modern research has had mixed results.
The ''
Pardachirus marmoratus'' fish (finless sole, Red Sea Moses sole) repels sharks through its secretions.
[ The best-understood factor is pardaxin, acting as an irritant to the sharks' gills, but other chemicals have been identified as contributing to the repellent effect.
In 2017, the US Navy announced that it was developing a synthetic analog of ]hagfish
Hagfish, of the Class (biology), class Myxini (also known as Hyperotreti) and Order (biology), order Myxiniformes , are eel-shaped Agnatha, jawless fish (occasionally called slime eels). Hagfish are the only known living Animal, animals that h ...
slime with potential application as a shark repellent.
History
Some of the earliest research on shark repellents took place during the Second World War
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, when military services sought to minimize the risk to stranded aviator
An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are also considered aviators because they a ...
s and sailor
A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term ''sailor'' ...
s in the water. Research has continued to the present, with notable researchers including Americans Eugenie Clark, and later Samuel H. Gruber, who has conducted tests at the Bimini Sharklab on the Caribbean island of Bimini
Bimini is the westernmost district of the Bahamas and comprises a chain of islands located about due east of Miami. Bimini is the closest point in the Bahamas to the mainland United States and approximately west-northwest of Nassau. The popula ...
, and the Japanese scientist Kazuo Tachibana. The future celebrity chef Julia Child
Julia Carolyn Child (Birth name#Maiden and married names, née McWilliams; August 15, 1912 – August 13, 2004) was an American chef, author, and television personality. She is recognized for having brought French cuisine to the American pu ...
developed shark repellent while working for the Office of Strategic Services
The Office of Strategic Services (OSS) was the first intelligence agency of the United States, formed during World War II. The OSS was formed as an agency of the Joint Chiefs of Staff (JCS) to coordinate espionage activities behind enemy lines ...
.
Initial work, which was based on historical research and studies at the time, focused on using 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,, initially packaged in cake form using a water-soluble wax binder and rigged to life vests. The Navy employed Shark Chaser extensively between 1943 and 1973. It is believed
that the composition does repel sharks in some situations, but not in all, with about a 70% effectiveness rating.
On the other hand, Albert Tester questioned the idea that dead shark bodies or chemicals based on them could work as shark repellent. In 1959, he prepared and tested extracts of decaying shark flesh on
. Tester found that not only did the dead shark extracts fail to repel any sharks, but several sharks had a "weak or strong attraction" to them. Tester reported a similar failure to repel sharks by a 1959 test at Enewetak of "an alleged shark repellent, supplied by a fisherman, which contained extract of decayed shark flesh as the principal component." Research has continued into the 2000s on using extracts from dead sharks or synthesizing such chemicals.