Spiny dogfish

Spiny dogfish Temporal range: 11–0  Ma[1] Late Miocene–present PreꞒ Ꞓ O S D C P T J K Pg N
Conservation status
Vulnerable  (IUCN 3.1)[2]
Imperiled  (NatureServe)[3]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Squaliformes
Family:	Squalidae
Genus:	Squalus
Species:	S. acanthias
Binomial name
Squalus acanthias Linnaeus, 1758
Range of the spiny dogfish (in blue)

The spiny dogfish (Squalus acanthias), spurdog, mud shark, or piked dogfish^[4] is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order.^[5]

While these common names may apply to several species, Squalus acanthias is distinguished by two spines (one

The spiny dogfish has dorsal fins, no anal fin, and white spot along its back. The

This shark is known to hunt in packs that can range up into the thousands. They are aggressive hunters and have a sizable diet that can range from squid, fish, crab, jellyfish, sea cucumber, shrimp and other invertebrates.^[8]

Dogfish sharks experience one of the longest gestation periods of any organism, which can last from around 18 to 24 months. During spawning season, which occurs during the colder months of winter, females can lay anywhere from 2 to 12 eggs, which develop

In females the size of ova and the state of uteri determines whether sexual maturity has been reached, while in males, clasper length and calcification is the determination factor. Many of the growth patterns show an isometric growth pattern, as the pups have very similar features to the adults. Sexual maturity does not match body size development, they mature quite earlier than one would expect. Most males reach sexual maturity at an earlier ages of around 10 years, growing to be about 60–65 cm in length. Females take a longer period of time, around 16 years, to reach sexual maturity, and can grow to about 80–84 cm (30–30 in) at that time. Some dogfish have been seen to live nearly 70 years, but the average lifespan is around 30–40 years.^[11][12] Male Spiny dogfish use their claspers to impregnate females, which take time to develop properly, and before reaching sexual maturity, tend to be longer than their pelvic fins. During this time, the testes develop, but no sperm will exist inside until later stages are reached, and genital ducts are deformed compared to adult ducts. Once the adult stage is reached, claspers have elongated, and are now hardened with calcium and are still slightly longer than their pelvic fin. At this point testes are fully developed, and sperm exist within the seminal vesicles, and genital ducts conform to a twisted shape we commonly see in adults.^[13]

Spiny dogfish are bottom-dwellers. They are commonly found at depths of around 50–149 m (160–490 ft), but have been found deeper than 700 m (2,300 ft).^[14]

Life span estimates based on analysis of vertebral centra and annuli in the dorsal spines range from 35 to 54 years.^[15]

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  Head
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  Jaws
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  Upper teeth
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  Lower teeth

Commercial use

Spiny dogfish are sold as food in Europe, the United States, Canada, New Zealand,

Spiny dogfish bodies are ground into fertilizer, liver oil and pet food. Because of their availability, cartilaginous skulls and small sizes, they are popular vertebrate dissection specimens in high schools and universities.

Reported catches varied between 31,700 tonnes in 2000 and 13,800 tonnes in 2008.

In the recent past^[when?] 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^[quantify] to rebuild the population.

In 2010,

In recent years, however, the US has implemented fishing controls and opened up the fishery.^[clarification needed] The proposed quota for 2011 was 16.1 million kilograms (35.5 million lb) with a trip limit of 1,800 kg (4,000 lb), an increase over past years in which the quota has ranged from 2 to 9 million kilograms (5 to 20 million lb), with trip limits from 900 to 1,400 kg (2,000 to 3,000 lb).^[24] In 2010, NOAA announced the Eastern US Atlantic spiny dogfish stocks to be rebuilt,^[25] and in 2011, concerns about dogfish posing a serious predatory threat to other stocks resulted in an emergency amendment of the quota with nearly 6.8 million kilograms (15 million lb) being added.^[26]

In June 2018, the New Zealand Department of Conservation classified Squalus acanthias Linnaeus as "Not Threatened" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.^[27]

In 2023, populations in EU and UK waters were determined to have recovered enough that they could be commercially fished.^[28]

Fossil range

This section needs expansion. You can help by adding to it. (June 2019)

Squalus acanthias fossils are known from the Miocene of Denmark and the Netherlands, dating from approximately 11 million years ago.^[1] As with other cartilaginous fish, the fossil record of Squalus acanthias consists predominantly of dental material, as cartilage does not fossilize well. The teeth of S. acanthus can be hard to differentiate from those of other squaliforme sharks,^[29] making identification difficult.

References