The bottlenose skate, spearnose skate, or white skate (''Rostroraja alba'') is a species of

skate Skate or Skates may refer to: Fish *Skate (fish), several genera of fish belonging to the family Rajidae * Pygmy skates, several genera of fish belonging to the family Gurgesiellidae * Smooth skates or leg skates, several genera of fish belongin ...

in the family Rajidae. It is a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

fish native to the coastal eastern Atlantic Ocean. Due to

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

, it has been depleted or extirpated in many parts of its former range in the northeastern Atlantic and the Mediterranean Sea, and is now endangered.

Distribution and habitat

The bottlenose skate is found along the coastlines of the eastern Atlantic Ocean, from the southern British Isles to South Africa and extends into the southwestern Indian Ocean to Mozambique. It is present as well in the western and northeastern sectors of the Mediterranean Sea. It is a

species of sandy and detrital bottoms, at depths of 40–400 m (exceptionally down to 500 m) from coastal regions to the upper continental slope. (1974) reported that it is more prevalent in rocky habitats.

Description

Most bottlenose skates are 60–150 cm long, with maximum recorded lengths of 230 cm for males and 202 cm for females. The flattened, angular pectoral fin fisc is about 1.4–1.5 times as broad as long. The

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...

is broad-based, abruptly tapering to a protruding sharp point and covered with small, sharp thorns. There are 40–45 rows of teeth in the upper jaw. The juveniles have 1 thorn before and 0–1 thorns behind the

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s and three rows of large thorns on the tail, 10–16 on the midline and 7–17 on either side. The adults have about 6 thorns around the inner margin of the orbit and 16–30 mid-dorsal and 17–29 lateral thorns on the tail. The skin is rough in adults except for a smooth patch in the center of the disc; the underside is prickly except for smooth patches on the snout. The young are entirely smooth, except for on the snout. Large juveniles and adults are greyish or bluish with or without numerous small white spots above, white below with brown to black disc margins. Hatchlings are plain reddish-brown above, often with blue spots, and white below with broad dusky disc margins.

Biology and ecology

The bottlenose skate is a benthic predator of

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

es, other elasmobranchs, fish offal,

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

s, mysids,

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttle ...

, and

cuttlefish Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of ...

. Younger, smaller fish are usually found in shallower water. Like other skates, this species is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

, with females producing 55-156 ova per year after a

gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it ...

of 15 months. The egg cases are oblong in shape, with stiff pointed horns at each corners and the larger horns flattened. They are deposited in sandy or muddy flats in the

spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a ...

. The capsules measure 12.5-18.3 cm long and 10.0-13.9 cm wide. This species is estimated to mature at 130 cm for males and 120 cm for females.

Relationship to humans

In the 17th century, the bottlenose skate was prized by the

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

for food. Because of its large size and slow reproductive rate, the bottlenose skate is extremely vulnerable to exploitation by

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

. Anecdotal data suggests that there has been a substantial decline in the abundance and geographical range of this species in the north Atlantic and Mediterranean. In the north Atlantic, populations of bottlenose skates have declined severely or disappeared from the

Bay of Biscay The Bay of Biscay (), known in Spain as the Gulf of Biscay ( es, Golfo de Vizcaya, eu, Bizkaiko Golkoa), and in France and some border regions as the Gulf of Gascony (french: Golfe de Gascogne, oc, Golf de Gasconha, br, Pleg-mor Gwaskogn), ...

and the Irish Sea; there are no longer targeted fisheries in these regions due to localized population collapses in the 1960s. There are also no recent records of this species in the waters off the United Kingdom, where it historically occurred. The bottlenose ray still persists along the coast of the Iberian Peninsula, though the population data is uncertain due to confusion with the shagreen ray (''Leucoraja fullonica'') and the sandy ray (''L. circularis''). In the Mediterranean, bottlenose skates of most size classes down to egg cases are taken as by-catch in multi-species trawling fisheries. Historically, it was caught frequently off the coasts of Tunisia and Morocco in the 1970s and was described as more or less frequent in the northwestern Mediterranean from the 1950s to the 1970s. The MEDITS trawl surveys, begun in 1985 and carried out six times a year in four geographic regions, indicates that the bottlenose skate is now very rare in the Mediterranean and that it has been reduced to a small fraction of its former range. The Italian National Group for Demersal Resource Evaluation (GRUND) survey captured this species infrequently in the Adriatic Sea. The species is assessed globally as Endangered in the IUCN Red List, and Critically Endangered in the northeast Atlantic. However, its status will require re-evaluation once data from its African range is available. In 2010, Greenpeace International added the bottlenose skate to its Seafood Red List, which includes commonly marketed species that "have a very high risk of being sourced from unsustainable fisheries".Greenpeace International Seafood Red List
. Greenpeace. Retrieved 15 February 2010.

References

{{Taxonbar, from=Q603663 bottlenose skate Fauna of the British Isles Fish of the East Atlantic Marine fish of Africa bottlenose skate Taxonomy articles created by Polbot