The Oxynotus centrina, commonly known as the Angular Roughshark, is a distinctive deep-sea shark species belonging to the family Oxynotidae. This deep-sea shark is a member of the order Squaliformes, which also includes dogfish sharks. Carl Linnaeus formally described the species in 1758, naming it for its sharp dorsal spines and keeled back.
Distinctive Physical Traits
The Oxynotus centrina possesses an unusual physical appearance. Its body is compressed, resulting in a triangular cross-section, and it features a broad, flattened head with a blunt snout. This gives the shark a somewhat “pig-like” facial appearance. Its skin is notably rough, covered in bristly dermal denticles.
It has two large, sail-like dorsal fins, each with a sharp spine. Its first dorsal fin is positioned far forward, above the head, with its spine oriented slightly forward. Enlarged ridges over its eyes expand into rounded knobs, studded with large denticles; these features are unique among rough shark species.
It also has large, vertically elongated spiracles nearly as tall as its eyes. It displays a uniform dark grey to grey-brown coloration, with adults sometimes showing darker blotches on the head and sides. A subtle light horizontal line often runs below its eyes on the cheek.
Habitat and Geographic Range
The Oxynotus centrina is a bathydemersal shark, living on or near the seabed in deep-water environments. It inhabits the outer continental shelves and upper slopes. It is found across a wide geographic range in the eastern Atlantic Ocean, extending from Norway southward to South Africa, including the Madeira and Canary Islands.
It is also present throughout the Mediterranean Sea, though its distribution can be variable. While it primarily occurs below 100 meters (330 feet), it has been recorded from 50 to 1,300 meters (160 to 4,300 feet). Studies in the Mediterranean indicate a preference for depths between 60 to 600 meters (200 to 1,970 feet), favoring coralline algal and muddy bottoms.
Feeding Habits and Lifestyle
The Oxynotus centrina is a slow-moving, bottom-dwelling species. Its high oil content in the liver provides buoyancy, reducing the need for constant forward motion. Its diet primarily consists of small benthic invertebrates and fish. Research indicates its diet largely comprises polychaetes and sipunculids, suggesting it functions as a suction feeder specializing in worm-like prey.
It also consumes teleosts, crustaceans, and echinoderms, indicating a varied, though specialized, diet. While observed consuming egg cases of other elasmobranchs, like the small-spotted catshark, this is an occasional behavior rather than a primary food source. Its relatively small mouth further suggests it preys on smaller organisms.
Conservation Status
The Oxynotus centrina is classified as Endangered globally by the IUCN Red List due to significant conservation challenges. In the Mediterranean, it is Critically Endangered due to severe population declines. It is particularly vulnerable to accidental bycatch in deep-sea fishing operations, especially by demersal trawl and longline fisheries. Its large dorsal fins and spines make it susceptible to entanglement in fishing nets; when released, it rarely survives.
Habitat degradation also contributes to its decline, as deep-sea ecosystems are increasingly impacted by human activities. Its slow reproductive rate further exacerbates its vulnerability; it is an ovoviviparous species, producing a small litter of 7 to 23 pups, with a minimum population doubling time estimated at over 14 years. Historical data from the Adriatic Sea, for example, show a significant decline, with the species once thought extinct there, though recent observations of juveniles offer hope. Despite its low commercial value, incidental capture remains a substantial threat to its diminished populations.