Piked dogfish (Squalus acanthias)

(Smith & Radcliffe, 1912).
Fr |
Aiguillat commun |
Sp |
Mielga; Agullat (Catalunya); Quissona
(Balearics); Aullat (Valencia) |
It |
Spinarolo; Ugghiata (Palermo); Arculate
(Rimini); Spinoelo (Liguria); Ferraro (Naples); Asią (Venice)
|
Ma |
Mazzola griza; Mazzola bix-xewka
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Diagnosis
A moderately large, slender and very abundant dogfish with two
spined dorsal fins, no anal fin and narrow rounded snout. Spine of
first dorsal fin shorter than that of second; origin of first spine
behind the pectoral free tips. Caudal fin without subterminal notch;
keels present on lower caudal peduncle. Well-developed precaudal pit
on dorsum. Upper and lower leeth rather similar and with oblique
cusps. Colour light or mid-grey above, lighter ventrally, with
conspicuous white spots on the body and no white tips or edges on
the dorsal fins.
Size
To about 150cm TL but generally much smaller, typically 120cm or
less; size at birth 22 to 33cm.
Status and Distribution
N.E. Atlantic: Common or abundant; cosmopolitan but
antetropical. Almost entire region over continental shelves, from
the boreal Arctic (Iceland and Barents Sea) southwards along all
European shores including the Baltic; Iberia south to African coast,
with southerly limits at Western Sahara; also insular at the
Canaries and Madeira. Mediterranean Sea Common or
abundant; cosmopolitan. Entire Mediterranean region; Sea of Marmara
and Black Sea.
Biology
An abundant and well-studied shark occurring both coastally and
offshore, also in estuaries and brackish zones but not penetrating
freshwater. Piked dogfish frequent waters from the intertidal zone
down to at least 950m, though generally shallower near the bottom
over sand, mud or fine gravel substrates and especially in the
vicinity of submerged banks. These sharks favour colder water
temperatures of between 7 to 15C and will migrate both vertically
and horizontally to remain within such an optimum range. Longer
distance seasonal migration is well-known in this species, both in
European seas and elsewhere. Often forming very large schools, the
piked dogfish, albeit a somewhat slow swimmer, is nevertheless
an active predator of a wide variety of teleosts, including clupeids
such as sardines and herrings, blennies, gadoids and flatfishes;
also cephalopods such as cuttlefish and squid, octopi, shrimps,
crabs, euphasiids, polychaetes and other benthic invertebrates. It
will also scavenge from bottom-set longlines, fish-traps and
nets. These sharks are themselves prey to a number of larger
sharks, both demersal and pelagic. Underwater remote video cameras
fitted to bottom-trawls have documented these sharks swimming at
considerable burst-speed in erratic vectors across the substrate in
an effort to evade capture; usually they are more sluggish. The
stock-structure of Northeastern Atlantic piked dogfish has been a
frequent source of investigation, not least given the commercial
importance of these sharks in a number of European fisheries. The
interelationship of the stocks remains uncertain and migratory
patterns may have shifted considerably over time, explaining in part
the often-varying results from tagging research conducted since the
early 1960's. There was sufficient evidence to once demonstrate the
existence of essentially two major stocks off the British Isles a
northerly stock, that migrated between the Irish Sea and Norway, and
a southern stock that frequented the English Channel and environs.
Today the situation is less readily discernable. These sharks also
shoal spatially and temporally by sex, which may again effect the
outcome of tagging studies where returns are gathered by commercial
fishing. An ovoviviparous species, with 2 to 11 young which are born
at a sex ratio of 11. Gestation period is 18-22 months, with females
giving birth once every two years. Females mature after ca. 10 years
at 70 to 100cm TL; males after ca. 11 years at 60 to 72cm.
The Shark Trust, 36 Kingfisher Court, Hambridge Road, Newbury, Berkshire, RG14 5SJ, UK.
Tel(+44) 01635 551150, Fax(+44) 01635
550230
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