Common thresher

Common thresher
Conservation status
Vulnerable  (IUCN 3.1)[1]
CITES Appendix II (CITES)[2]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Lamniformes
Family:	Alopiidae
Genus:	Alopias
Species:	A. vulpinus
Binomial name
Alopias vulpinus (Bonnaterre, 1788)
Confirmed (dark blue) and suspected (light blue) range of the common thresher[3]
Synonyms
Squalus vulpinus Bonnaterre, 1788 Squalus vulpes Bonnaterre, 1788 Squalus vulpes Gmelin, 1789 Alopecias vulpes (Gmelin, 1789) Alopias vulpes (Gmelin, 1789) Carcharias vulpes (Gmelin, 1789) Galeus vulpecula Rafinesque, 1810 Alopias macrourus Rafinesque, 1810 Squalus alopecias Gronow, 1854 Alopecias barrae Perez Canto, 1886 Alopecias longimana Philippi, 1902 Alopecias chilensis Philippi, 1902 Vulpecula marina Garman, 1913 Alopias caudatus Phillipps, 1932 Alopias greyi Whitley, 1937 Alopias superciliosus (non Lowe, 1841) misapplied Alopias pelagicus (non Nakamura, 1935) misapplied[4]

The common thresher (Alopias vulpinus), also known as Atlantic thresher, is the largest species of thresher shark, family Alopiidae, reaching some 6 m (20 ft) in length. About half of its length consists of the elongated upper lobe of its caudal fin. With a streamlined body, short pointed snout, and modestly sized eyes, the common thresher resembles (and has often been confused with) the pelagic thresher (A. pelagicus). It can be distinguished from the latter species by the white of its belly extending in a band over the bases of its pectoral fins. The common thresher is distributed worldwide in tropical and temperate waters, though it prefers cooler temperatures. It can be found both close to shore and in the open ocean, from the surface to a depth of 550 m (1,800 ft). It is seasonally migratory and spends summers at lower latitudes.

The long tail of the common thresher, the source of many fanciful tales through history, is used in a whip-like fashion to deliver incapacitating blows to its prey.^{[citation needed]} This species feeds mainly on small schooling forage fishes such as herrings and anchovies. It is a fast, strong swimmer that has been known to leap clear of the water, and possesses physiological adaptations that allow it to maintain an internal body temperature warmer than that of the surrounding sea water. The common thresher has an aplacental viviparous mode of reproduction, with oophagous embryos that feed on undeveloped eggs ovulated by their mother. Females typically give birth to four pups at a time, following a gestation period of nine months.

Despite its size, the common thresher is minimally dangerous to humans due to its relatively small teeth and timid disposition. It is highly valued by commercial fishers for its meat, fins, hide, and liver oil; large numbers are taken by longline and gillnet fisheries throughout its range. This shark is also esteemed by recreational anglers for the exceptional fight it offers on hook-and-line. The common thresher has a low rate of reproduction and cannot withstand heavy fishing pressure for long, a case in point being the rapid collapse of the thresher shark fishery off California in the 1980s. With commercial exploitation increasing in many parts of the world, the International Union for Conservation of Nature has assessed this species as vulnerable.