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Thresher shark (Alopias vulpinus)

Thresher shark - Alopias vulpinus

© Ian K Fergusson

(Bonnaterre, 1788).
Fr Renard; Faucheur
Sp Zorro; Tiburon zorro blanco; Rabosa (Catalunya); Cinturo (Balearics); Peix espasa (Majorca)
It Squalo volpe; Pesci rattu (Liguria); Pavone (Salerno); pesce bandiera (Rimini); Pisci cudutu (Messina)
Ma Pixxivolpi; Budenb

Diagnosis

Upper lobe of caudal fin greatly elongated and tapering almost whip-like, its length typically equi-sized or slightly exceeding trunk length. Snout short, rounded and conical with moderately-sized eyes that are not dorsally-expanded; labial furrows present at corners of mouth; no grooves on  the anterior dorsum above the gills (compare with A. superciliosus). 1st dorsal fin anterior origin above pectoral rear free tips.  Colour slate-grey dosally, with an irridescent structural sheen on the flanks of freshly-caught examples; white ventrally, with a strong, variable line of demarcation between the two pigments associated with blotching typically around the pelvic fins; ventral white pigment extends along the flanks above the pectoral fins. Undersides of pectoral fins and pelvic fins often darkly-blotched.

Size

Maximum total length 550cm and  possibly to 600cm; most specimens typically  200 to 500cm; size at birth 114 to 150cm TL.

Status and Distribution

Mediterranean Sea: Common or frequent. Entire western Mediterranean to Sicily; somewhat rarer off southern Tunisia and increasingly sporadic further east to Libya and Egypt. Sicilian Channel and Malta Channel (sometimes locally abundant). Cosmopolitan in the Ionian Sea, also both sides of the Adriatic where it ranges to the northern extremes;  Balkan peninsula coasts, Aegean Sea, Turkey, Dodecanese and Cyprus; scarcer off Lebanon and Israel.

Biology

The thresher shark is an epipelagic species, both coastal and offshore over continental slopes where it ranges from the surface down to at least 366m. They will readily approach the shoreline following schools of fish and penetrate shallow bays or narrow passes between islands. In the summer months, especially in the still conditions such as typify the northern Adriatic off Venice and Rimini, these sharks can often be seen swimming at the surface with their long caudal fin scything the water, apparently whilst actively feeding upon small fish that seem to "boil" ahead of the shark. There are reports of this species leaping clear of the surface and it is clearly cabable of high speed dashes. Assumedly, the elongate tail is utilised as a specialised tool for feeding, whereby the thresher first herds and then stuns schooling fish with strong sweeping blows. Essentially piscivorous, feeding on clupeids such as sardines; scombroids such as mackerel; also garfish and lanternfishes; cephalopods, octopuses, infrequently crustaceans and even seabirds. Ovoviviparous; litter size 2 to 4; full-term pregnant females taken off western Sicily and elsewhere; nursery-zone in Northern Adriatic during the summer months.  Females mature at 370 cm +; males at 319cm +. [an error occurred while processing this directive]