Species IUCN · Vulnerable (VU)

Spiny Dogfish

Squalus acanthias, Linnaeus, 1758

marinebrackish

About Spiny Dogfish

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

While these common names may apply to several species, Squalus acanthias is distinguished by two spines (one anterior to each dorsal fin) and no anal fin. It lives in shallow waters and further offshore in most parts of the world, especially in temperate waters. Those in the northern Pacific Ocean were reevaluated in 2010 and found to constitute a separate species, now called the Pacific spiny dogfish (Squalus suckleyi).

Appearance

The spiny dogfish has dorsal fins, no anal fin, and white spots along its back. The caudal fin has asymmetrical lobes, forming a heterocercal tail.

The species name acanthias refers to the shark's two spines. These are used defensively. If captured, the shark can arch its back to pierce its captor with spines near the dorsal fins that secrete a mild venom into its predator.

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.

Habitat

Squalus acanthias fossils are known from the Miocene of Denmark and the Netherlands, dating from approximately 11 million years ago. 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. acanthias can be hard to differentiate from those of other squaliforme sharks, making identification difficult.

Humans & conservation

Once the most abundant shark species in the world, populations of Squalus acanthias have declined significantly. They are classified in the IUCN Red List of threatened species as Vulnerable globally and Critically endangered in the Northeast Atlantic, meaning stocks around Europe have decreased by at least 95%. This is a direct result of overfishing to supply northern Europe's taste for rock salmon, saumonette, and zeepaling. Despite these alarming figures, very few management or conservation measures are in place for Squalus acanthias. In EU waters, a Total Allowable Catch (TAC) has been in place since 1999, but until 2007 it only applied to ICES Areas IIa and IV. It was also set well above the actual weight of fish being caught until 2005, rendering it meaningless.