Pacific Spiny Dogfish - Squalus acanthias

Pacific Spiny Dogfish

View all Pacific Spiny Dogfish Images in the Pacific Marine Index

The Spiny Dogfish, Squalus acanthias, is a small coastal shark of the second largest shark order known as Squaliformes.  In this order there are seven families, and at least 130 species.  The Spiny Dogfish is a member of the family Squalidae, which also has the common name of Dogfish Sharks. 

All dogfish have a slender, cylindrical, and slightly flattened body type. No member of this family has an anal fin, and all species have two dorsal fins with 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. The body of this species is counter shaded, 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 rounded snout), somewhat small and straight sitting, with teeth that 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 Spiny Dogfish is a small schooling shark that forms groups of hundreds or even thousands of individuals of the same sex and size. Tagging studies have determined that they migrate great distances, as individuals tagged off of Newfoundland were recovered in Iceland years later. There have also been records of transatlantic crossings, however the bulk of the population migrates seasonally along the coastal regions of North America. 

These fish inhabit the colder waters of the Atlantic and Pacific oceans from the shallows to nearly 2400 ft. (700 m.) deep. In the Pacific, Spiny Dogfish range from the Bering Sea to Baja California, with greatest abundance along the coast of British Columbia and Washington. During the summer months, divers will frequently encounter these sharks in the shallows hunting for a meal. 

Anyone wishing to get a photograph of these skittish little sharks must possess a great deal of patience, along with the willingness to give these creatures some space. In the past, underwater photographers have ventured to fish processing plants that would dump fish remnants into the water. This practice would attract hundreds of dogfish to the area where getting images was quite easy. Since this practice has now stopped, it is increasingly difficult to find large numbers of dogfish and to capture great images. The Spiny Dogfish is curious by nature, however they will dart away if they feel even slightly threatened.