Spiny dogfish - Squalus acanthias

 

spiny dogfish

 

Diagnostic characters: Body elongate and spindle-shaped. Snout and head narrow, snout pointed; anterior nasal flap narrow; distance from tip of snout to inner corner of nostril slightly more, about equal, or slightly less than that from inner corner of nostril to upper labial furrow; spiracle large, halfmoon-shaped; mouth only very slightly arched.Teeth alike in both jaws, small, compressed, and with a single cusp deeply notched outward end strongly oblique. Skin smooth, denticles on sides of body narrowand unicuspid in young but broad and tricuspidate in adults.A strong, long spine without lateral grooves on anterior margin of both dorsal fins; origin of first dorsal-fin spine behind pectoral-fin rear tips; second dorsal fin much smaller than first; pectoral fins narrow and falcate or semifalcate, free rear tips of pectoral fins narrowly rounded, posterior margins of fins weakly to moderately concave; midbases of pelvic fins much closer to origin of second dorsal fin than to insertion of first dorsal fin. Caudal peduncle flattened below, with an obscure longitudinal keel low down on each side; upper precaudal pit strongly developed, no lower precaudal pit. Caudal fin without a subterminal notch. Colour: bluish grey or grey above and lighter grey to whitish below, white spots or dashes often present on sides (occasionally absent in adults); dorsal fins with black apical patches and white posterior markings in young but plain or with dusky tips in adults; iris green.

Size: Maximum total length exceptionally to about 200 cm but most adults smaller than 130 cm; size at birth 18 to 33 cm; size at maturity 52 to over 104 cm for males and 66 to over 120 cm for females, varying in different populations.

Habitat, biology, and fisheries: A common to abundant dogfish on the continental and insular shelves and upper and middle slopes of boreal to subtropical seas, at depths from the intertidal to possibly 1 446 m, with a tendency to occur close inshore in higher latitudes and in deep water closer to the equator; recorded depths in the area 8 to 619 m. Highly mobile and migratory, showing seasonal migrations along the Atlantic coast of North America. Ovoviviparous, number of young 1 to 32. Feeds primarily on bony fishes, both demersal and pelagic, but also eats small cartilaginous fishes, cephalopods, crustaceans, gastropods, bivalves, polychaete worms, sea cucumbers, jellyfish, and comb jellies.Caught in bottom trawls and with limited importance to fisheries in Area 31 compared to other areas of the North Atlantic where massive catches occur. Relatively small catches of dogfish (310 to 4 500 t per year, including this species) were reported by the USA to FAO during the past decade.

Distribution: In Area 31 this dogfish occurs off the Atlantic coast of the USA from North and South Carolina, Georgia, and Florida, with an important wintering ground in deep water; occasionally caught off Cuba and the Bahamas. In the western Atlantic it ranges from Greenland and Labrador, Canada to Florida, USA, the Bahamas, and Cuba, also off Uruguay and Argentina. Widely distributed in temperate and subtropical parts of most oceans.