Spiny dogfish
Encyclopedia
The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known of the dogfish
which are members of the family
Squalidae
in the order Squaliformes
. While these common names may apply to several species
, Squalus acanthias is distinguished by having two spines (one anterior to each dorsal fin
) and lacks an anal fin. It is found mostly in shallow waters and further offshore in most parts of the world, especially in temperate waters.
The species name acanthias refers to the shark's two spines. These are used defensively. If captured, the shark can arch its back to pierce its captor. Glands at the base of the spines secrete a mild poison.
Males mature at around 11 years of age, growing to 80–100 cm (2.6–3.3 ft) in length; females mature in 18–21 years and are slightly larger than males, reaching 98.5–159 cm (3.2–5.2 ft). Both sexes are greyish brown in color and are countershaded
. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or "claspers". The male inserts one clasper into the female cloaca during copulation.
Reproduction is aplacental viviparous, which was before called ovoviviparity
. Fertilization is internal. The male inserts one clasper into the female oviduct orifice and injects sperm along a groove on the clasper's dorsal section. Immediately following fertilization, the eggs are surrounded by thin shells called "candles" with one candle usually surrounding several eggs. Mating takes place in the winter months with gestation lasting 22–24 months. Litters range between 2 and 11 but average 6 or 7.
, the United States
, Canada
, New Zealand
and Chile
. The meat is primarily consumed in England
, France
, the Benelux
countries 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 this and other dogfish are sold in fish and chip shops as "rock salmon" or "huss", in France it is sold as "small salmon" (saumonette) and in Belgium and Germany it is sold as "sea eel" (zeepaling and Seeaal, respectively). It is also used as fertilizer, liver oil, and pet food, and, because of its availability, cartilaginous skull, and manageable size, as a popular vertebrate
dissection specimen, in both high schools and universities.
In the recent past the European market for spiny dogfish has increased dramatically, which led to the overfishing and decline of the species. This drastic increase led to the creation and implementation of many fishery management policies placing restrictions on the fishing of spiny dogfish. However, since the species is a late maturing fish, it takes a while to rebuild the population.
In 2010, Greenpeace International has added the spiny dogfish to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."
In recent years however, the US has implemented fishing controls and opened up the fishery. The current proposed quota for 2011 is 35.5m lbs. with a trip limit of 4000 lbs. This is a gain over past years in which the quota has ranged from 5-20m lbs. with trip limits from 2000- 3000 lbs.. In 2010, NOAA announced the Eastern US Atlantic Spiny Dogfish stocks to be rebuilt and in 2011 concerns about dogfish posing a serious predatory threat to other stocks resulted in an emergency amendment of the quota with nearly 15 million pounds being added .
Squaliformes
Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...
which are members of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Squalidae
Squalidae
Squalidae is the family of dogfish sharks. They are found in the Atlantic, Pacific, and Indian oceans, from tropical equatorial climates to the Arctic and Antarctic....
in the order Squaliformes
Squaliformes
Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...
. While these common names may apply to several species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, Squalus acanthias is distinguished by having two spines (one anterior to each dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
) and lacks an anal fin. It is found mostly in shallow waters and further offshore in most parts of the world, especially in temperate waters.
Morphology and behavior
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 the shark's two spines. These are used defensively. If captured, the shark can arch its back to pierce its captor. Glands at the base of the spines secrete a mild poison.
Males mature at around 11 years of age, growing to 80–100 cm (2.6–3.3 ft) in length; females mature in 18–21 years and are slightly larger than males, reaching 98.5–159 cm (3.2–5.2 ft). Both sexes are greyish brown in color and are countershaded
Countershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...
. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or "claspers". The male inserts one clasper into the female cloaca during copulation.
Reproduction is aplacental viviparous, which was before called ovoviviparity
Ovoviviparity
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...
. Fertilization is internal. The male inserts one clasper into the female oviduct orifice and injects sperm along a groove on the clasper's dorsal section. Immediately following fertilization, the eggs are surrounded by thin shells called "candles" with one candle usually surrounding several eggs. Mating takes place in the winter months with gestation lasting 22–24 months. Litters range between 2 and 11 but average 6 or 7.
Commercial use
Spiny dogfish are fished for food in EuropeEurope
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
and Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. The meat is primarily consumed in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, the Benelux
Benelux
The Benelux is an economic union in Western Europe comprising three neighbouring countries, Belgium, the Netherlands, and Luxembourg. These countries are located in northwestern Europe between France and Germany...
countries and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. 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 this and other dogfish are sold in fish and chip shops as "rock salmon" or "huss", in France it is sold as "small salmon" (saumonette) and in Belgium and Germany it is sold as "sea eel" (zeepaling and Seeaal, respectively). It is also used as fertilizer, liver oil, and pet food, and, because of its availability, cartilaginous skull, and manageable size, as a popular vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
dissection specimen, in both high schools and universities.
Conservation Status & Management
Once the most abundant shark species in the world, populations of Squalus acanthias have declined significantly. They are classified in the IUCN Red List of threatened species as Vulnerable globally and Critically Endangered in the Northeast Atlantic, meaning stocks around Europe have decreased by at least 95%. This is a direct result of overfishing to supply northern Europe's taste for Rock Salmon, Saumonette or Zeepaling. Despite these alarming figures, very few management or conservation measures are in place for Squalus acanthias. In EU waters, a Total Allowable Catch (TAC) has been in place since 1999, but until 2007 it only applied to ICES Areas IIa and IV. It was also set well above the actual weight of fish being caught until 2005, rendering it meaningless. Currently (2009), the TAC stands at 316t for ICES Areas IIa & IV, 104t for ICES Area IIIa and 1,002t for ICES Areas I, V - VIII, XII & XIV. In addition, a maximum landing size of 100 cm has been imposed in order to protect the most valuable mature females. The European Commission has stated that the TAC for 2010 will be set at 0t, ending targeted fishing for the species in EU waters. It remains to be seen if populations will be able to recover.In the recent past the European market for spiny dogfish has increased dramatically, which led to the overfishing and decline of the species. This drastic increase led to the creation and implementation of many fishery management policies placing restrictions on the fishing of spiny dogfish. However, since the species is a late maturing fish, it takes a while to rebuild the population.
In 2010, Greenpeace International has added the spiny dogfish to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."
In recent years however, the US has implemented fishing controls and opened up the fishery. The current proposed quota for 2011 is 35.5m lbs. with a trip limit of 4000 lbs. This is a gain over past years in which the quota has ranged from 5-20m lbs. with trip limits from 2000- 3000 lbs.. In 2010, NOAA announced the Eastern US Atlantic Spiny Dogfish stocks to be rebuilt and in 2011 concerns about dogfish posing a serious predatory threat to other stocks resulted in an emergency amendment of the quota with nearly 15 million pounds being added .
External links
- http://video.msn.com/v/us/v.htm?g=2F3EEE6E-6ED5-444C-8A74-6A0899FA0B85&f=msnhome&fg=copySpiny dogfish attacked by Giant Pacific Octopus
- Spiny dogfish at Animal Diversity Web