Spiny Dogfish - Squalus acanthias
Status: Vulnerable … Considered to be critically endangered in the NE Atlantic.
Location: Spiny dogfish are a temperate cosmopolitan species, distributed throughout the NE, NW and South Atlantic, the North Sea, the Mediterranean Sea, Black Sea and the temperate Pacific Ocean.
Size: Up to 2 metres in length, but usually between 110 and 124cm in the North Atlantic
Habitat: Not associated with any particular habitats, but found in coastal waters and open ocean, and most common in waters between 10 and 200 metres in depth.
Other names: Spurdog, Spotted Dogfish, Piked Dogfish, Rock Salmon, White-spotted Dogfish.
Main Threats: Once considered the world’s most abundant elasmobranch (sharks and rays) species, the spiny dogfish has suffered serious population declines throughout its range, especially in the north east Atlantic, where 95% declines in their population have been recorded and where it is now considered critically endangered. The main threat is from commercial overfishing by various gears, but especially by towed gear, which can also damage spiny dogfish habitat. They were a valuable fishery, with great demand in western Europe. In the UK, like other species of shark, spiny dogfish was commonly sold in fish and chip shops as ‘rock salmon’. Like other elasmobranches, dogfish are slow to mature, long-lived and have low reproduction rates, making them very vulnerable to over-exploitation.
In the north east Atlantic, commercial targeting of spiny dogfish has been prohibited by the EU since 2011, and vessels are required to record any accidental bycatch and discard of spiny dogfish when it exceeds 50kg. However, bycatch still regularly occurs, and because spiny dogfish shoal in dense packs, they can be accidentally caught and killed in huge numbers as bycatch by trawlers targeting other species. The UK is now considering piloting new reactive fishery methods to try and address the problem. While it is illegal to land spiny dogfish in the EU, it is still legal to import it from other countries that permit capture, and so can still be traded in the UK, where it may still be sold as ‘rock salmon’.
Female spiny dogfish mature at 12 years old, while males mature at 6 years old. Gestation is thought to be between 18 and 22 months, one of the longest recorded pregnancies for any vertebrate. Spiny dogfish give birth to a litter of live ‘pups’ numbering between 1 and 20, and measuring between 18 and 30cm. After they are born they disperse, and the shoals segregate themselves by size, with the smaller, younger specimens staying closer to the surface and the larger dogfish living deeper. Once they reach sexual maturity, the males and females segregate by sex and size, with females staying mid-water and moving to shallower waters to give birth, while the males stay further offshore and deeper.
In the UK, they may be sold in fish and chip shops as ‘rock salmon’. Say “no, thanks” to rock salmon if you see it on the menu!
Did you know?
- Spiny dogfish diet varies depending on where they live. In the north east Atlantic they feed mainly on bony fish, whereas in New Zealand they feed mainly on crustaceans such as squat lobster.
- The spiny dogfish gets its name from the two large ungrooved spines on each dorsal fin, which have venom glands at their base and are used primarily for defence.
- In spite of the spines and venom glands, the spiny dogfish do have a few enemies, including larger sharks, some large predatory fish species, seals and killer whales.
- Spiny dogfish are highly migratory, with populations seasonally migrating within regions, with some tagging studies recording trans-Atlantic migrations.
What MCS is doing:
- Working with the fishing industry, government, chefs and restaurants, consumers and retailers to promote sustainable seafood;
- Advising consumers to avoid eating spiny dogfish through Fishonline and the Pocket Good Fish Guide;
- Working for a network of marine protected areas in UK waters to protect spiny dogfish habitats.