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Thresher shark tail

Thresher shark tail

Thresher shark

Thresher sharks are large lamniform sharks of the family Alopiidae found in all temperate and tropical oceans of the world; the family contains three extant species, all within the genus Alopiaso.All three thresher shark species have been listed as vulnerable to extinction by the World Conservation Union since 2007 (IUCN). .orThe three extant thresher shark species are all in the genus Alopias. The possible existence of a hitherto unrecognized fourth species was revealed during the course of a 1995 allozyme analysis by Blaise Eitner. This species is apparently found in the eastern Pacific off Baja California, and has previously been misidentified as the bigeye thresher. So far, it is only known from muscle samples from one specimen, and no aspect of its morphology has been documented.

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en.wikipedia.org)Thresher sharks are large lamniform sharks of the family Alopiidae found in all temperate and tropical oceans of the world; the family contains three extant species, all within the genus Alopias. (Source:

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.thresher shark, (genus Alopias), any of three species of sharks of the family Alopiidae noted for their long, scythelike tails that may constitute almost one-half their total length. Thresher sharks are found in tropical and temperate seas throughout the world. They feed on squid and schooling fishes, attacking after circling and herding their prey into small groups. They sometimes use their tails to stun their prey or, by thrashing the water, to frighten it. They are not generally considered dangerous to man. The best-known species is the long-tailed thresher, or (Source: www.britannica.com)

The Common Thresher Shark (Alopias vulpinus) is virtually circumglobal, with a noted tolerance for cold waters. This species is especially vulnerable to fisheries exploitation (target and by-catch) because its epipelagic habitat occurs within the range of many largely unregulated and under-reported gillnet and longline fisheries, in which it is readily caught. It is an important economic species in many areas and is valued highly for its meat and large fins. Its life-history characteristics (2–4 pups per litter; 8–14 year generation period) and high value in both target and bycatch fisheries make it vulnerable to rapid depletion. Serious declines have occurred where this species has been heavily fished, for example in the 1980s eastern central Pacific drift gillnet fishery, where reported landings collapsed to 27% of peak levels between 1982 and the late 1980s. Analyses of pelagic longline CPUE data from logbook reports covering the species’ entire range in the northwest and western central Atlantic vary according to the time period, but suggest thresher shark stocks declined by between 63–80% during 1986–2000. There is evidence that thresher sharks are being increasingly targeted by pelagic fisheries for swordfish and tuna (e.g., in the Mediterranean Sea) in attempts to sustain catches, and exploitation is increasing in these areas. The high value of the species and its exploitation by unmanaged fisheries combined with its biological vulnerability, indicate that at least some, if not most, subpopulations in other parts of the world are likely to be equally, or more seriously at risk than those for which data are available and, unlike the Californian stock, are not the subject of management, enabling stocks to rebuild. (Source: www.marinebio.org)

 

 

 

 

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