- Scientific name: Squalus acanthias
- Also known as: Spiny Dogfish, Spiked Dogfish, Cape Shark, Piked Dogfish.
- Size: Up to 4ft and 20lbs (UK shore caught typically 5-10lbs)
- UK minimum size: 23inches (58cm) in length
- UK shore caught record: 16lb 12oz
- IUCN Status: VU (Vulnerable)
- Distribution: Found in temperate waters around most of the UK, but more prominent around the western coast of England, Scotland and Ireland. Spurdog are also found in many other places around the world (see below).
- Feeds on: Fish such as small flounder, plaice, codling and sprats, but will also feed fish that swim in midwater such as herring and eat small crustaceans.
- Description: Slender shark species which can be grey to brown on back and flanks with sometimes with white spots and has a pale underbelly. Prominent pectoral fins which lack rays, spines or segments and no anal fin is present. Two dorsal fins, both of which contain a spike which secretes venom. Five gill slits are present on each side of the body.
Spurdog can be found in deep water, although they will move into relatively shallow water to feed, when they can come within range of the shore angler. Spurdog will spend most of their time hunting on or near the seabed for bottom dwelling fish such as small flatfish and cod, although they will venture into midwater to feed on herring, sprats and sandeels, especially in summer months when this type of prey is more abundant. Evidence exists that spurdog move around in shoals, and may cover large distances when searching for food. They are one of the few venomous fish in UK waters (along with the stingray and weever fish), with the spines behind the two dorsal fins secreting a venom which can cause swelling and discomfort in humans. Occasionally on a still summer night it is possible to see spurdog swimming slowly just below the surface of the water.
Suprdog have a wide worldwide distribution and are found in many separate populations around the world. The European population extends all around Scandinavia, Britain and throughout the Mediterranean, and includes areas of north Africa and Greenland and Iceland. Other populations are found on the east and west coasts of the USA, around Brazil, Chile, Argentina and Uruguay in South America. There are also populations off the coast of Australia and New Zealand, around China, Japan and South Korea, and in the Baring Sea off the coast of Russia. While the distribution of the spurdog is still widespread, the numbers and population density of this species is greatly reduced from previous levels.
Commercial Value and Conservation Status
Spurdog were once one of the most common shark species in British waters. However, the increasing demand for spurdog on the European market led to commercial long-liners relentlessly targeting this species, while British trawlers caught spurdog as bycatch. Supurdog are used commercially in a number of different ways: their flesh is prepared for human consumption, the livers used for fish oil and the fins used for shark fin soup. This has had the effect of spurdog numbers reducing dramatically from the 1970s. Today they are classed as Vulnerable with a declining stock population by the International Union for the Conservation of Nature. Some action has been put in place to protect spurdog – since 2010 the species has had a zero Total Allowable Catch (TAC) imposed by the European Union, meaning that commercial fishermen have not been allowed to retain any spurdog which they catch. However, this does not mean that spurdog do not get caught. In August 2015 a trawler fishing out of Newlyn caught an estimated ten tons of spurdog while trawling for John Dory off the Isles of Scilly, with all of the fish being discarded. Like most shark species the spurdog is a long lived, late maturing and slow growing species, which makes it vulnerable to commercial exploitation – see Reproduction section below for further details.
Anglers who are lucky enough to catch a spurdog should return it to the sea to try and help conserve stocks. Like the bull huss the spurdog is sometime sold as ‘rock salmon’ in fish and chip shops and fishmongers to hide the fact they are selling an endangered species, and in other parts of the world its fins are used for cheap versions of shark-fin soup.
Spurdog mate in the winter months. Once the eggs of the spurdog have been fertilised they remain inside the female for up to 22 months – one of the longest gestation periods in the animal kingdom. Because spurdog eggs hatch inside of the female this makes it look as if the spurdog give birth to live young in the same way that mammals do. This long gestation period and late sexual maturity (ten years for males, up to fifteen for females – although there is evidence that some spurdog have still not reproduced at thirty years) means that spurdog numbers will take a very long time to recover, even if stringent protection measures are put in place and commercial fishing for this species is severely limited. Once born the young spurdog have a yolk sac attached to the side of their body which supplies them with nutrients and sustenance until they are big enough to fend for themselves.
Techniques and Methods to Catch Spurdog
Although spurdog are often targeted by boat anglers they can be caught from the shore in some parts of the country, with the deep seawater lochs in the west of Scotland a favoured venue. Hooks of 2/0 – 4/0 are generally used, with heavy 80lb+ mono, or even wire hooklengths used to prevent the sharp teeth of the Spurdog cutting through the line. Simple, single hook rigs are the best choice, with hooks clipped down with bait clips or impact shields to allow further distances to be reached and aid bait presentation. Fish baits such as mackerel strip, full herring, sandeel and blueys are all used, and success can also be had with squid, cuttlefish and peeler crab. Anglers should always be careful when landing a spurdog as it may thrash its body around and arch its back in an attempt to use its spines to defend itself. This is a good reason to keep rigs simple as overly complex rigs are likely to get tangled up by the flailing spurdog.