Spiny Dogfish Shark

Average size between 80 cm and 110 cm, total maximum length about 160 cm. Small shark with two dorsal fins with ungrooved large spines. No anal fin. First dorsal spine origin is behind the pectoral rear tips. Lateral keels on caudal peduncle and upper precaudal pit. No subterminal notch on the caudal fin. No anal fin.
Display grey-brown upper body with whitish ventral surface coloration. White spots along entire body.

A well studied species. This is probably the most abundant shark species of all. Lives preferably close to bottom. Slow swimming. Found over the continental and insular shelves and upper slopes down to approximately 900 m. This species can tolerate brackish water and is often found in enclosed bays and estuaries. The species name acanthias refers to the shark's two spines. These are used defensively. If captured, the shark can arch its back to pierce its captor. Glands at the base of the spines secrete a mild poison. Feeds mainly on fishes, preferably schooling fishes, invertebrates, cephalopods, crustaceans, and even sea cucumbers and jellyfishes.

Aplacental viviparous (ovoviviparous). Fertilization is internal. The male inserts one clasper into the female oviduct orifice and injects sperm along a groove on the clasper's dorsal section. Immediately following fertilization, the eggs are surrounded by thin shells called "candles" with one candle usually surrounding several eggs. Mating takes place in the winter months with gestation lasting 22–24 months. Litters range between 2 and 11 but average 6 or 7. Size at birth about 20 cm. Sexual maturity is reached at an age of about 20 years (sometimes even later) or a size of about 60 cm.

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