Spiny dogfish (Squalus acanthias)

Spiny dogfish (fig. 1), also known as spurdogs or piked dogfish, are globally one of the most common shark species (Scottish Government, 2011). They tend to live in the benthic zone of the water column, near the seabed of continental shelves and slopes (OSPAR Commission, 2008). They are known to migrate between deeper waters in the winter, and shallower waters in the summer. (The Wildlife Trusts, n.d.)

Niche and Distribution: 
At 1.6m when fully grown, spiny dogfish are a large dogfish species (Scottish Government, 2020), preying on bony fish or other sharks (The Wildlife Trusts, n.d.).                                                                                               As shown in fig. 2, they are mostly found around coastal areas where continental shelves occur (IUCN Red List, 2018), in generally higher latitude waters. They are found along most of the European and Mediterranean coastlines. Pockets also occur in southern regions of South America, Africa, Australia and Greenland, as well as along the East coast of the USA, and around New Zealand.                                                Additionally, in recent years a population of Spiny dogfish have been identified permanently residing inland within Loch Etive on the West of Scotland. Only females were identified year round, suggesting the site is perhaps a breeding location, and part of a migratory route for the species (Thorburn et al, 2015). 

Breeding:
As with most Shark, Skate and Ray species, spiny dogfish have a very slow reproductive process. They reach maturity at between 10 and 20 years old, and undergo a gestation period of between 1.5 to 2 years (Shark Trust, 2020). However, compared to some other species (e.g. porbeagle sharks which give birth to minimal pups per litter), spiny dogfish can birth between 1 and 32 (Shark Trust, 2020). They will have a litter once every 2 years (OSPAR Assessment Portal, 2021). 

Abundance and threats: 
Globally, spiny dogfish are classed as vulnerable (IUCN Red List, 2018). In the Northeast Atlantic however, they are now considered recovered to the extent that a target fishery was announced in 2023.This update follows 10 years of management after the population crashed in the latter half of the 20th century - a result of overfishing. Accordingly, Shark Trust is advising caution to prevent numbers crashing once again (Shark Trust, 2023).
As such, the major risks to the spiny dogfish population now include targeted fishing, bycatch and habitat degradation of their seabeds by trawling and dredging. (OSPAR Assessment Portal, 2021).