Introduction to the Angular Roughshark
The angular roughshark (Oxynotus centrina) is a small, distinctively spiny deep-sea shark of the family Oxynotidae. Its ridged back and large, spined dorsal fins give it a rugged profile that sets it apart from smoother sharks of similar size. Inhabiting temperate and tropical waters of the northeastern Atlantic and parts of the Mediterranean, it favors outer continental shelves and upper slopes, typically below 50 m. This profile explains key biological traits, distribution, ecology, threats, and current conservation status, providing a durable reference for those interested in deepwater shark biology and protection.
Identification and Morphology
Angular roughsharks are small sharks, commonly under 100 cm total length, with a stout body and a somewhat flattened appearance. Their name comes from keeled, spiny scales (denticles) arranged in angular ridges along the back. Two large, spine-bearing dorsal fins stand tall, and the snout is blunt with nasal flaps covering mouthparts when closed. Eyes are large and reflective, suited to low-light depths. The caudal fin is short, and the skin is rough to the touch. These features make adults recognizable in life and in bycatch.
Distribution and Habitat
Angular roughsharks occur in the eastern Atlantic from Norway and the British Isles to South Africa, including the Mediterranean Sea. They are most common on the outer parts of the continental shelf and upper slope, at depths roughly 50 to 600 m, often near mud, sand, or rock substrates. Preferred temperatures generally fall between approximately 8–17°C, though records extend into warmer southern areas. Juveniles may occupy shallower, inshore habitats, while adults utilize deeper, cooler waters.
Geographic Hotspots
- Northeastern Atlantic continental slope off Portugal and Spain
- Mediterranean Sea, especially western basins
- Celtic Sea and waters around the British Isles
- Iberian and Moroccan margins
Behavior and Ecology
Angular roughsharks are sluggish, bottom-oriented sharks that spend much of their time resting or slowly cruising above the substrate. They are ovoviviparous, retaining eggs internally until live young are born. Their sensory systems include enlarged spiracles that may help in low-oxygen water and specialized lateral-line canals to detect movement and vibrations in dark, near-bottom environments. As relatively small sharks, they are not a threat to humans and pose no danger to divers or fishers.
Diet and Feeding
Angular roughsharks feed on small benthic invertebrates and fish, with diet varying by size and region. Juveniles tend to consume more crustaceans, while adults include cephalopods, small bony fishes, and occasional echinoderms. They locate prey using electroreception and mechanosensory cues, then seize and crush items with robust teeth designed for grasping. Feeding activity peaks during twilight and at night when prey is more active in the water column.
Prey Types Observed
| Prey Group | Representative Examples | Regional Variation |
|---|---|---|
| Crustaceans | Mysid shrimp, amphipods | Common across range |
| Cephalopods | Small squids and octopuses | Higher in warmer areas |
| Bony Fish | Gobies, small gadoids | Local availability dependent |
| Echinoderms | Sea cucumbers, brittle stars | Occasional, not primary |
Reproduction and Life History
Angular roughsharks are ovoviviparous, with females carrying developing embryos in egg capsules within the uterus. Litter sizes are small, typically 7–10 pups, though some reports suggest ranges of 6–15 depending on female size. Newborns measure roughly 13–15 cm and grow slowly, reaching maturity at approximately 70–90 cm for females and slightly smaller sizes for males. Estimated longevity is up to 15–20 years, but precise growth rates and age at maturity remain uncertain due to limited data.
Conservation Status and Threats
The IUCN Red List currently classifies Oxynotus centrina as Near Threatened globally, reflecting uncertainty and concern about bycatch in deepwater trawl and gillnet fisheries. Although they are not targeted commercially, angular roughsharks are often discarded, with unknown post-release survival. Habitat impacts from bottom disturbance and potential climate-driven changes in temperature and oxygen may affect deep-sea populations. Regional protection in some Mediterranean areas exists, but consistent monitoring and bycatch reduction measures are needed across their range.
Key Conservation Points
- Bycatch in deepwater fisheries is the primary threat.
- Low reproductive output increases vulnerability to population declines.
- Limited basic biology hampers effective management strategies.
- Improved observer coverage and bycatch reporting can support recovery.