Deep in the Northeast Atlantic Ocean is where you’ll find the Sailfin Rough Shark (Oxynotus paradoxus), although it is uncommon. Also known as the Kite-Fin Shark, it is one of four species that make up the small rough shark family (Oxynotidae). These deep-water sharks are weak swimmers that use their large, oil filled livers to stay buoyant.
The Rough Sharks all belong to a larger group of species known as Order Squaliformes, the Dogfish Sharks. Members of this order have a short snout, five gill slits, two dorsal fins that usually bear sharp spines, and no anal fin. They also lack nictitating membranes, which are the extra, clear eyelid that some sharks have for eye protection.
This particular species has a body that is triangular in cross-section with a broad, flat head. The skin is dark brown with no distinct markings. The typical length of adults is about 1.2 m (4 ft).
Sailfin Rough Shark Facts
The first dorsal spine leans backward, which distinguishes it from the only other rough shark in the Northeast Atlantic: the Angular Rough Shark (O. centrina).
The shape of the spiracles (modified gill slits) is another distinguishing characteristic. They are relatively small and almost circular, compared to the large, longer shape found in the Angular Rough Shark.
Habitat and Range
Map Of The Sailfin Rough Shark’s Habitat
The Sailfin Rough Shark lives in the very deep waters of the Northeast Atlantic. It has been recorded off the British Isles, France, Spain, Portugal, the Canary Islands, and south to West Africa. Catch data from fishing reports show that it is rarely found in inshore waters. Rather, it is captured most often at depths of 500-600m (1665-2000 ft).
More recent Sailfin observations, on the mid-Atlantic ridge around the Azores Islands, show that the distribution extends further west than was originally thought. These records also suggest the species may be present along the entire floor of the Northeast Atlantic, deeper than was thought.
Little information is known about the diet of this shark, other than it eats small invertebrates and fishes that live in the same habitat, on the ocean bottom.
It is believed that the Sailfin might have a spring reproductive migration from deeper waters where it usually stays (from 265 to 720 m / 880 to 2400 ft) to the continental shelf, but evidence of that is lacking.
This is an ovoviviparous species, whose live pups are about 25cm long (10″). No other information is available about this shark’s reproductive behavior.
Humans and Conservation
The main way that people encounter this species is when fishermen occasionally take it as bycatch in trawls. Handling requires special care because of the sharp teeth and large dorsal spines.
The species has little commercial value, and it can be turned into fishmeal. Although it isn’t a target species, however, a growing trend for deepwater fisheries could pose a greater risk to all fish that use ocean bottom habitats. This could be of particular concern for species like the Sailfin that are not abundant.
The IUCN Red List classifies this shark as “Data Deficient”, because so little is known about its natural history. Further research will be needed to shed light on its full geographic range, population biology, and life history, before the impact of fishing can be evaluated. As such, no conservation or management measures are currently in place.
The same can be said for most of the mysterious creatures that inhabit the depths of marine ecosystems: the ocean bottom is the next frontier, just waiting to be explored!
Written By: Kara Levevre
Azevedo J, Sousa FL & Brum JM (2003). Dermal denticles and morphometrics of the sailfin roughshark Oxynotus paradoxus (Elasmobranchii, Oxynotidae), with comments on its geographic distribution. Cybium 27:117-122.
Castro JI, Woodley CM & Brudek RL (1999). A Preliminary Evaluation of the Status of Shark Species. FAO Fisheries Technical Paper 380.
Shark Trust (2010). An Illustrated Compendium of Sharks, Skates, Rays and Chimaera. Chapter 1: The British Isles and Northeast Atlantic. Part 2: Sharks.http://www.sharktrust.org/en/factsheets/45/sailfin-roughshark/
Soldo A & Freitas M (2009). Oxynotus paradoxus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2.