Thresher sharks, also called thrasher
sharks, derive their name from their uniquely elongated tail (caudal) fin
. It is a peaceful shark and normally keeps to itself, unless provoked by any enemy.
Like most sharks, threshers frequent tropical waters
, although they prefer cooler climates. Although not entirely nocturnal, they mostly hunt at night
They thrive in tropical and temperate waters and are found in virtually every ocean in the world, excluding the barren expanses of the south Pacific.
Classification of Thresher SharksKingdom
: A. vulpinus, A. pelagicus, A. superciliosus
✏ Thresher sharks are lamniform sharks
, a group they share with great white sharks and mackerel sharks.
✏ Common thresher sharks have a blue-gray body
on the upper side and a white underbelly
. According to the species, the upper body can vary between shades of gray and blue, while the underside can also be gray, although usually not in conjunction with a grey upper body.
✏ They have very small jaws
but, typical of sharks, sharp teeth. The size of jaws renders these shark harmless against humans, although the long tail fin can cause significant damage if met in full force.
✏ The elongated caudal fin is unique to threshers and helps to identify them in the sea.
✏ The tail fin of threshers is usually one-third of the total body length, and can reach up to half of the body
✏ They have 2 dorsal fins, a large pectoral fin and 5 gill slots.
✏ They can grow up to 6 m
and an weigh as much as 1100 lbs
, although usually specimens are much smaller than these extreme limits.
✏ They are strong, fast swimmers and even have the ability to leap out of water
, a behavior known as porpoising
. They are one of the few sharks that are able to fully jump out of the water.
✏ Like many sharks, threshers have a system to maintain a higher body temperature than the surroundings
, despite being cold-blooded. They can maintain a temperature 1° - 5°
higher than their surroundings
✏ They feed on crustaceans
, squids, octopi and other small fish. They primarily hunt schools of fish
, by threshing
the seabed around the schools, raising the mud and thus disorientating the fish. The shark then easily picks off the best of the fairly stationary lot.
✏ Threshers can also use their tail to strike a prey, stunning or even killing it.
✏ Like most sharks, threshers are ovoviviparous
, i.e., the egg remains in the mother's body while the offspring develops in it. Unlike placental animals, such as human beings, the embryos are not fed through an umbilical cord, but by the egg yolk
. When the young ones exhaust their yolk sac, they feed on the mother's unfertilized eggs. The newborn sharks are generally 110 - 150 cm
✏ A healthy female usually produces 2-4 healthy pups.
✏ No particular season has been observed as a specific 'mating season'.
✏ Male thresher sharks reach maturity in 10-15 years, whereas the females take more time.
✏ The life span of thresher sharks is usually 30-40 years
Thresher sharks have been declared a vulnerable species
by the International Union for Conservation of Nature (IUCN) since 2007.
They have been exploited on a large scale for commercial purposes. Their meat, liver oil and fins are in great demand in the market. In America, South Africa, Baja (California) and Mexico they are also used for recreational purposes. This is despite the fact that as apex predators, shark meat is often laden with mercury, which can cause severe disorders in humans.
Sharks are one of the oldest surviving inhabitants of the earth. They are a tough, resourceful and intelligent breed of fish and have survived tough environmental changes, including the ones that killed off the incumbent dinosaurs.
It is of utmost importance that we preserve these unique sharks. Since sharks are apex predators, their presence in an ecosystem is an indicator of the good health of the ecosystem in general. It should be remembered that one less shark equals a lot more damage to the environment than is visible at first glance.