Thresher Shark

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Thresher Shark

Thresher sharks inhabit temperate coastal waters in the Atlantic and Pacific Oceans. They mainly feed on schools of smaller fish, such as sardines and anchovies, as well as squid and mollusks. They whip their tail around to stun their prey. The average lifespan of a thresher shark in the wild is 25 years.


Content List

1. Scientific & Common Names

2. Characteristics

a. Breeding

b. Behavior

3. History

4. Present Status

5. References


Scientific & Common Names

Kingdom - Animalia

Phylum - Chordata

Class - Chondrichtyes

Subclass - Elasmobranchii

Family - Alopidae

Genus - Alopias

Species - Alopias vulpinus (Common Thresher Shark), Alopias pelagicus (Smalltooth or Pelagic Thresher), Alopias superciliosus (Bigeye Thresher)

Common Names - Sea Fox, Fox Shark, Thrasher, Swiveltail


Characteristics

Thresher sharks have a long upper tail fin, which is their most distinctive feature. These extended fins can be as long as the entire rest of the shark's body. They range from gray to dark brown in color, with white bellies and a green, blue or purple dorsal fin, depending on the species. Bigeye thresher sharks have enlarged eyes, while pelagic thresher sharks have longer snouts and narrower heads. Common thresher sharks are the largest species, with adults measuring between 5 and 19 feet long and weighing an average of 766 pounds.


Breeding

Thresher sharks breed annually and do not appear to have a specific breeding season. The young develop in eggs that the mother carries inside her until they are ready to hatch. Females typically produce one or two offspring at a time and are not involved with caring for them once they are born. Thresher sharks grow slowly, with males reaching reproductive maturity when they are 9 or 10 years old and females maturing when they are 12 or 13 years old.


Behavior

Thresher sharks often stay in shallow water during the night and spend their days in deeper water. They also migrate away from the equator in summer and toward it in winter. These sharks do not usually interact with other members of their species except to breed. They rely on their sense of smell, a lateral line that detects movement, and electromagnetic senses to find prey. Thresher sharks are shy and are not considered a threat to humans. Common and pelagic threshers are sometimes known to leap several feet out of the water, in an act known as breaching, for unknown reasons.


History

Thresher sharks are still present in much of their historic range, but their numbers are decreasing due to fishing. They are in high demand for their meat, fins and liver oil.


Present Status

The common thresher shark, bigeye thresher shark and pelagic thresher shark are all listed as vulnerable. In addition to being targeted by unmanaged recreational and commercial fisheries, their populations are also declining due to a slow rate of recovery. Conservation efforts to protect these species include enforcing stricter fishing regulations and implementing bans on shark finning.


References

   http://animaldiversity.ummz.umich.edu/accounts/Alopias_vulpinus/
   https://www.flmnh.ufl.edu/fish/Gallery/Descript/ThresherShark/ThresherShark.html
   http://www.iucnredlist.org/details/full/39339/0
   http://www.iucnredlist.org/details/161597/0
   http://www.iucnredlist.org/details/161696/0
   Sharks of the World, 2005, Leonard Compagno and Sarah Fowler
   The Sharks of North America, 2011, Jose I. Castro