Spiny Dogfish Shark
Squalus acanthias
(A.K.A. Horned Dog, Piked Dogfish, Spurdog, Rock Shark, Rock Cod, & Rock Salmon)

• Spiny dogfish are gray to slate brown with a pale or white belly.
• They can be differentiated from other small sharks by a row of small white dots running along their sides.
• If these dots are faded or absent, which can happen with older dogfish, a distinctive single spine found in front of each of their two dorsal fins can be used as an additional identifying feature.
• The bodies of these fish are slender and their heads slope to a blunt snout. 
• It is interesting that these sharks are referred to as "Spiny Dogfish" Sharks.
• They differ from the Smooth Dogfish Shark by having spines in front of each dorsal fin as well as rows of white dots along the side, both of which are lacking in the Smooth Dogfish Shark.
• The presence of the spines in front of each dorsal fin certainly explains the ‘Spiny' part of the common name.
• However, it is the shark's gregarious nature, occurring in ‘Packs' of hundreds or thousands of individuals, that explains where the 'Dogfish' comes from.

• In size, adult females can reach lengths of 3 1/2 feet and weigh around 8 pounds, while males are normally smaller in size.

• The Spiny Dogfish Shark is the world's most abundant shark, occurring worldwide in temperate and sub-arctic ocean waters.
• They prefer water temperatures from a low of around 7 - 8 degrees Centigrade (45 - 46 Fahrenheit) to a high of 12 - 15 degrees Centigrade (54 - 59 Fahrenheit).

• They occur in oceans and coastal zones but rarely enter the upper reaches of estuaries.
• They never occur in fresh water.

• Spiney dogfish shark are powerful, voracious predators that feed primarily on bony fishes.
• Principal food are members of the Clupeidae (Herring family), Ammodytes (sand lances), Osmeridae (smelts) and Euphasids (a krill like ocean shrimp).
• Twenty-seven other fish species, many being of commercial importance, fall prey to the Spiny Dogfish shark as do over 13 species of invertebrates including squid, lobster, and crabs.
• The effect of their presence on other species is generally negative, resulting in displacement.

• Spiney dogfish shark mate in winter.
• Females are ovoviviparous (produce eggs that hatch within the body) and have a gestation period of 18 - 24 months, the longest of any vertebrate.
• They generally have from 1 to 20 pups, with an average of about 6 - 7, with each being 18 - 30 cm. (9 - 12") in length.
• It is known the these sharks (Spiny Dogfish) tend to school by size when smaller and by sex when they mature.
• Females of the species mature in about 10 years at length of 70 - 100 centimeters (27 - 40").
• Males mature in 11 years at a size of 60-72 centimeters (24 - 28").
• Some researchers have estimated the life expectancy of this shark to be from 25 - 100 years.

• This is a species that is described by recreational fishers simply as "Undesirable".
• The gregarious nature of this shark usually results in multiple catches once the first one has been caught.
• Their increasing presence will usually result in the fisher moving to a different location because all they can catch is spiny dogfish.
• This is especially annoying in our area to fishers who target wrecks in pursuit of black seas bass, tautog, and other structure preferring species.
• The spiny dogfish is usually released or discarded by the recreational fishers although there are some who find them quite edible.
• The commercial fishery for spiny dogfish shark in the state of Maryland is presently non-existent.
• For current recreational size and creel limits, see Maryland's updated regulation page.

• Presently, the spiny dogfish shark is declared a species in need of conservation in Maryland.
• Fins of this species are used as sandpaper for fine sanding of wood materials.
• When in Europe, if you order "Fish & Chips", you will probably be eating spiny dogfish.
• Watch out for those two dorsal spines, they are mildly venomous.

• This long-lived species is also the most studied of all the sharks no doubt due in part to their use as a dissection subject in the classroom.

For information concerning spiny dogfish shark and their management, please contact Mike Luisi. 

Illustration courtesy of the Maine Department of Marine Resources
Recreational Fisheries Program and the Maine Outdoor Heritage Fund