dogfish

dogfish, name for a number of small sharks of several different families. Best known are the spiny dogfishes (family Squalidae) and the smooth dogfishes (family Triakidae). Spiny dogfishes have two spines, one in front of each dorsal fin, and lack an anal fin. The common spiny, or piked, dogfish (Squalus acanthus) is found in most oceans of the world and is particularly abundant in shallow, temperate waters. Its gray skin is speckled with white. Females of this species may reach a length of 4 ft (120 cm) and weigh 15 to 20 lb (6.3-9 kg); males are smaller. The spines in this species contain venom that can cause a very painful wound. Spiny dogfishes migrate seasonally, preferring water within a certain temperature range. They feed on a variety of fishes and invertebrates and cause great damage to populations of commercially valuable fish. In Europe they are fished for food. Other members of the spiny dogfish family are found in deep water. The smooth dogfish (Mustelis canis) is found on the Atlantic coast of America from Brazil to Cape Cod. It is gray in color and grows to a length of about 5 ft (150 cm). Of no commercial value, it migrates seasonally and feeds on small fishes and invertebrates. Like the spiny dogfish, the smooth dogfish is much used for dissection by students of vertebrate anatomy. The smooth dogfish family also includes two small sharks abundant on the Pacific coast of the United States, the brown smoothhound (Rhinotriacis henlei ) and the leopard shark (Triakis semifasciata); the latter is strikingly marked with black on a tan background. The name dogfish also refers to certain unrelated bony fishes (see bowfin). The dogfish sharks are classified in the phylum Chordata, subphylum Vertebrata, class Chondrichthyes, order Selachii.

Any of several species of small sharks. The spiny dogfish (Squalus acanthias, family Squalidae) has a sharp spine in front of each of its two dorsal fins. It is abundant along northern Atlantic and Pacific coasts. It is gray with white spots, about 2–4 ft (60–120 cm) long, and often found in schools. It preys on fishes and invertebrates and often steals bait and damages fishing nets. It yields liver oil or is ground for fertilizer. Other well-known species are the spotted dogfishes (family Scyliorhinidae), which are sold as food, and the smooth hound or smooth dogfish (Mustelus canis, family Triakidae), one of the most common sharks on the U.S. Atlantic coast. Seealso bowfin.

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In freshwater lakes and rivers, "Dogfish" refers to a member of the Bowfin family.

Dogfish is a name applied to a number of small sharks found in the northeast Atlantic, Pacific, and Mediterranean, especially to those in the three families Scyliorhinidae, Dalatiidae and Squalidae. Although often used in reference to Scyliorhinus canicula, the name is applied only loosely and does not usually signify a close taxonomic relationship.

Anatomy and morphology

The spiny dogfish, Squalus acanthias, is the most common shark in the western Atlantic. It is a small, slender shark with a flattened head and a snout that tapers to a blunt tip. It averages 2 1/2 to 3 ft in length with the largest growing to 4 ft or more. It hunts both alone and in groups with other dogfish. It eats small fish, squid, and crustaceans, and has extremely strong jaws for crushing shells, with low, flat, grinding teeth like the smooth dogfish, but also possessing an extra set of small, very sharp teeth. Records show that they can live from 25 to 30 years. More common is the lesser-spotted dogfish, with the nursehound (greater spotted-dogfish) less abundant.

Interaction with humans

Dogfish are considered a nuisance by fishermen because they will latch on to almost anything put in the water, including human hands. Fishermen used to kill them when caught which, along with pollution, has contributed to a sharp decline in population in Puget Sound. It is now illegal to kill or mutilate them when caught even though they were once considered a delicacy by Europeans, their flesh being sold as "rock salmon".

Care must be taken when handling dogfish due to the two venomous spines at the back of both dorsal fins. The venom is not likely to cause major damage, but the wound can take months to heal. Their skin is also extremely abrasive, and thus gloves are usually worn when handling live dogfish .

See also

• Scyliorhinidae
• Dalatiidae
• Squalidae

References

• Dogfish UK
• Spiny Dogfish and other Sharks