Spiny Dogfish

 

Animal Unique | Spiny Dogfish | The Spiny dogfish, dogfish, piked dogfish or mud shark, is one of the best known of the dogfish, which are members of the family are in the order Squaliformes. Although these common names apply to different species, Spiny dogfish is distinguished by having two spines (one anterior to each dorsal fin) and lacks an anal fin. It occurs mainly in shallow waters and further offshore in most parts of the world, especially in temperate waters. More is known about it than other types of sharks, it has been widely studied in scientific laboratories. It is extensively used by people as food, fertilizer, hide, pet food, oil and liver.

Scientific classification
Kingdom:     Animalia
Phylum:     Chordata
Class:     Chondrichthyes
Subclass:     Elasmobranchii
Order:     Squaliformes
Family:     Squalidae
Genus:     Squalus
Species:     S. acanthias

The Spiny dogfish has dorsal spines, no anal fin, and white spots along its back. The caudal fin has asymmetrical lobes, forming a heterocercal tail. The species name acanthias refers to two of the shark spines. These are used defensively. If caught, the shark can arch its back to pierce his Captor. Glands at the base of the spines secrete a mild poison. Both sexes are gray-brown in color and are counter shaded. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or "claspers". The man adds a rank in the female cloaca during copulation.

The smooth teeth of Spiny dogfish are located in rows which rotate into use as needed. The first two rows are used in obtaining prey, the other rows rotate into place when needed. If lost teeth, broken or worn, they are replaced by new teeth that rotate into place. The Spiny dogfish is an opportunistic feeder eat whatever prey is abundant. In general, their diet is small fish such as capelin, cod, haddock, hake, herring, menhaden and ratfish. They also eat invertebrates such as krill, crabs, polychaete worms, jellyfish, ctenophores, amphipods, squid and octopus.

This shark is present in all the world's temperate oceans It ranges in the coastal waters of the Atlantic and Pacific. The Spiny dogfish is a seasonal migrant into Canadian waters. In June these sharks appear off Nova Scotia in the Bay of Fundy and off southwestern Newfoundland. In July they move into the Gulf of St. Lawrence and in waters off southern Labrador and around the rest of Newfoundland. By late fall most of the dogfish migrate out of Canadian waters and to the south to the waters off North Carolina and New England. Spiny dogfish are not considered dangerous, but some damage can be done through their teeth and their slightly poisonous dorsal fin spines. Spiny dogfish are gregarious (social) and travels in schools of hundreds to thousands of individuals. These schools are often segregated by gender and age. They are called dogfish because they travel and hunt in packs. They migrate in schools, after cool water.

Spiny dogfish are caught for food in Europe, the United States, Canada, New Zealand and Chile. The meat is mainly in England, France, Benelux and Germany. The fins and tails are processed into fin needles and are used in less expensive versions of shark fin soup in Chinese cuisine. In England Spiny dogfish and other dogfish are sold in fish and chip shops as "rock salmon" or "Huss", in France it is sold as "small salmon" in Belgium and Germany and is sold as "sea eel". It is also used as fertilizer, liver oil and pet food, and because of the availability, cartilage skull, and the manageable size, such as a popular vertebrate dissection specimen, in both high schools and universities.

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