Spiny dogfish have a gray or brown top and pale grey or white ventral side with irregular white spots on the body. Essentially the spiny dogfish are torpedo-shaped and are streamlined to permit easier swimming mobility. The average length of spiny dogfish is 30 to 40 inches however some individuals attain a size of 50 inches in length and a weight of 20 pounds. The second dorsal fin is smaller than the first and both fins have spines at their origins. The caudal fin is asymmetrical with the upper lobe being larger. Spiny dogfish have pectoral fins with curved rear margins and they possess no anal fin. The smooth edged, short and oblique teeth are the same in both jaws. Spiny dogfish have a lifespan of 30 years.
Spiny dogfish are opportunistic feeders which feed upon whichever prey is abundant. Small fish such as capelin, herring, menhaden, hake, haddock, ratfish and small cod comprise the bulk of their diet. As well, spiny dogfish consume krill, crabs, polychaete worms, jellyfish, ctenophores, amphipods, squid and octopus. Pacific giant octopus have been known to turn the tables and consume spiny dogfish. Large sharks also consume spiny dogfish. The spiny dogfish can be located in the water column from the surface to depths of 2,400 feet. Being very tolerant of a range of salinities, the spiny dogfish can also be found in estuaries. Spiny dogfish are very migratory and have been known to cross the Atlantic Ocean.
Development in this shark is ovoviviparous and most litters are between 2 and 16 individuals that are approximately 8 to 12 inches in length. Sexual maturity in males is reached at 31 to 39 inches at which time they are eleven years old. Female spiny dogfish reach sexual maturity between 18 and 21 years of age by which time they are 39 to 49 inches in length. Young are born in the warmer waters off North Carolina or New England during the winter months. The spiny dogfish carries it's pups in the womb ( gestation period ) for 22 months, longer than the gestation period for any other shark. The number of pups born in a litter is dependent on the size of the female shark, larger females bearing more pups.
During the 1990s there was massive overfishing of spiny dogfish stocks all along the eastern seaboard. In January, 2011 there was a ban place upon fishing spiny dogfish stocks and the stocks are still considered to be in bad shape and recovering slowly.
photo courtesy of DFO