spinydogfish.org - About Spiny Dogfish

	About Spiny Dogfish The spiny dogfish, Squalus acanthias Linnaeus 1758, is a small coastal shark of the second largest shark order known as Squaliformes (Dogfish Sharks). In this order are seven families and at least 100 species. The spiny dogfish is a member of the family Squatinidae, which also has the common name of Dogfish Sharks. There are at least 70 species in this family, and the family itself is very diverse ranging from small to large species. However, all species typically are slender with a cylindrical or slightly flattened body. No member of the family has an anal fin, and most species have two dorsal fins with no spines. The spiny dogfish has a large spine on each dorsal fin, and its many common names reflect this unique body feature. Other common names include the spurdog, piked dogfish, codshark, thornshark, skittledog, spotted dogfish, and white spotted dogfish. In gourmet restaurants that serve this species, it is referred to as “northern shark”. The scientific name is from the Latin squalus (shark) and the Greek akanthias (referring to the spines).
	Other notable features of the spiny dogfish are described here. The body is countershaded, with slate gray or brown on the dorsal surface grading into white or dirty white on the ventral surface. Younger fish typically have several rows of white spots on the dorsal and sides, which may disappear with age. The mouth is inferior (underneath the snout), somewhat small and straight. The snout is rounded. The teeth are rather small and arranged in two or three functional rows. The five gill slits are low on the body positioned anterior to the pectoral fins. The spiracle is just dorsal and posterior to the eye. The placoid scales are small and irregularly spaced on the body.
	The spiny dogfish inhabit colder waters of the Atlantic and Pacific oceans from shallows to nearly 700 m deep. In the northern hemisphere, the species is found on both the eastern and western sides of the oceans. In the Pacific spiny dogfish range from the Bering Sea to Baja California, with greatest abundance along British Columbia and Washington. In the eastern Atlantic, they range from Norway to Senegal with greatest abundance in the North Sea and adjacent coastal waters. In the western Atlantic, they range from Labrador and Newfoundland to Florida and Cuba, with greatest abundance from North Carolina to Nova Scotia. In the Southern Hemisphere, the spiny dogfish is found off Argentina along the Patagonian coastline. In the picture at left, red areas represent higher probabilities of occurance for spiny dogfish.
	Spiny dogfish exhibit extensive seasonal migration along the North American coastline, overwintering along the Outer Banks of North Carolina and spending summers in new England and Atlantic Canada. These fish seem to prefer water temperatures in the 43-47^o F range. A similar pattern may occur in the southern hemisphere along the Patagonian coastline, and tagging studies are needed to confirm this pattern. Extensive tagging studies for populations in the eastern Pacific and eastern Atlantic suggest that these populations do not exhibit the extensive coastal migrations of their western Atlantic coast cousins. This may be a result of the prevailing cold ocean currents along the eastern edges of the oceans, and the seasonably changing temperatures (the warm Gulf Stream and cold Labrador Current) along the North American coastline (a similar seasonal temperature shift occurs along Patagonia).