Spiny Dogfish Shark
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Worldwide Distribution


Summary
Scientific Name
Squalus acanthias
Classification
Phylum: Chordata
Class: Chondrichtyes
Subclass: Elasmobranchii
Order: Squaliformes
Family: Squalidae
Genus and Species: Squalus acanthias
Species Authority: (Linnaeus, 1758)
Range
Circumglobal; Boreal to warm-temperate waters
Occurrence in Canadian Waters
Very Common
Population Trend
Interaction with Humans
Directed fishery and bycatch in commercial fisheries
Conservation Status
COSEWIC: Special Concern (2010)
SARA: Under Review
IUCN Global: Vulnerable (2006)
CITES: Appendix II
Fisheries Vulnerability: Very High
IUCN Regionally: Endangered (2006)

Description

The spiny dogfish is one of the most abundant demersal shark species in Atlantic Canada and may be the most abundant shark species worldwide. This shark is a major predator on several commercially significant species such as herring, Atlantic mackerel and squid. As such, they have long been considered a nuisance by fishermen because they interfere with fishing operations, as they cause damage to fishing gear and are regularly caught as bycatch in several fisheries.

The spiny dogfish is a small schooling shark that forms groups of hundreds, even thousands, of individuals of the same sex and size. It is grey or brownish on top and pale grey or white on its bottom side with sporadic white spots on the top and sides of its body.

Habitat

Found in cold and warm temperate oceans at temperatures between 0 and 15 °C. The spiny dogfish may also be found in a variety of habitats (e.g. estuaries), as it can tolerate a wide range of salinities and may be located in inshore and offshore continental shelf areas, commonly at depths of 10 to 200 metres, and in the water column from the surface to depths of 730 metres. On the Scotian Shelf, this shark has most often been caught in water temperatures between 6 and 11 °C.

Distribution

Spiny dogfish range throughout the Canadian coastal waters of the Atlantic and Pacific oceans. In the Atlantic waters, spiny dogfish are most abundant between the Scotian Shelf with some populations in the Gulf of St. Lawrence. The species is most abundant between Nova Scotia and Cape Hatteras.

Although some stocks undertake long-distance seasonal migrations, their distribution is fragmented into distinct populations. Therefore, spiny dogfish can be either a resident or a seasonal migrant into Canadian waters. Most of the dogfish in Canadian waters move inshore in the summer and offshore in the winter, but remain in Canadian waters. Semi-resident aggregations occur off southern Newfoundland, in the Gulf of St Lawrence and on the Scotian Shelf.

Spiny Dogfish Shark Fishery

Spiny dogfish, exploited on both coasts, represent a primary commercial interest. It has been harvested for the last 100 years for its oil rich liver; however, today spiny dogfish is valued as food in many countries. Before 1979, Canadian landings of spiny dogfish were small; however, with declining fin fish stocks and a small foreign market for dogfish, a new directed fishery began in 2002 with an initial quota of 2,500 tonnes. With greater interest from Canadian fishermen in 2003, the total allowable catch was increased to 3,200 tons and a 5-year research plan was established to collect scientific data. By 2004, quota was reduced to 2,500 tonnes where it remains today. The fishery itself generally begins in the late spring when dogfish schools begin to migrate northward and continues into the summer and early fall. Dogfish are usually harvested by longline or handlines, however, gillnets and otter trawls have been used in the past.

As spiny dogfish are considered to be groundfish under the groundfish integrated fisheries management plan, they are subject to different management measure than other sharks. To date, quotas are based on past catch data, rather than scientific catch limits. In addition, no bycatch limits have been established, despite high bycatch rates. More information on the spiny dogfish fishery can be seen on the Canadian Shark Research Laboratory shark fisheries page.

A Species at Risk?

As a very long-lived, slow-growing and late to mature shark, spiny dogfish are particularly vulnerable to fishing and slow to recover from over-exploitation. The major threat to this species in Atlantic Canada is bycatch. These sharks are commonly caught in bottom trawls, gillnets, longlines and other line gears, as well as by sport fishers. Segregation of the species by size and sex also makes aggregations of large females at risk to fisheries. As the Canadian stock of spiny dogfish is a distinct population, as a whole, the population has not declined, but generally remains above long-term average abundance.

Did You Know?

The name "spiny dogfish" comes from the fact that dogfish have one sharp spine in front of both of their two dorsal fins.