|Scientific Name:||Leucoraja circularis|
|Species Authority:||(Couch, 1838)|
Raja circularis Couch, 1838
|Taxonomic Notes:||Formerly called Raja circularis. Early papers often confused Leucoraja circularis and Leucoraja naevus.|
|Red List Category & Criteria:||Vulnerable A2bcd+3bcd+4bcd ver 3.1|
|Assessor/s:||Ungaro, N., Serena, F., Ellis, J., Dulvy, N., Tinti, F., Bertozzi, M., Mancusi, C. & Notarbartolo di Sciara, G.|
|Reviewer/s:||Cavanagh, R.D., Valenti, S.V. & Kulka, D.W. (Shark Red List Authority)|
Leucoraja circularis is a relatively large skate, found in the northeast Atlantic and Mediterranean Sea. Traditionally, it was thought to be found mainly around 100 m depth on sandy and muddy bottoms, though it has been suggested that it is now favours slightly deeper waters. This species is taken as bycatch of multi-species trawl fisheries and offshore bottom longlines. The occurrence of L. circularis in the Mediterranean appears to have decreased significantly in the last 50 years. From 1957–1960 it was recorded in 10–17% of trawl samples in the Gulf of Lions and in 1948 it was recorded in 3.2% of trawl samples in the Adriatic sea. The species appears to be no longer present in these areas. Mediterranean-wide scientific trawl surveys from 1995-1999 recorded this species in only 12 of 6,336 trawls. Benthic trawl effort has increased significantly during the last 50 years and fishing pressure continues within this species’ depth range. The current rarity of this species in the Mediterranean, evidence of local extirpation from the two locations covered by the historical comparative trawl surveys, and its likely low intrinsic rate of increase suggested by its large body size and large size at maturity suggest that it is Endangered in this region. In the Northeast Atlantic, this species is relatively rare, and it is also taken as a bycatch of multi-species trawl fisheries. French landings data for this species have declined from about 500 tonnes per year in the early 1990s to about 300 tonnes per year. Species-specific landings data prior to this are not available. English surveys in the North Sea and Celtic Sea have not recorded this species since 1996 and 1997 respectively, although it is still recorded in various Scottish surveys around northwestern Scotland. Most of the recent captures of this species in Scottish surveys have been made in waters of 180–500 m depth, suggesting that the main part of the distribution is now in deeper water, along the edge of the continental shelf and on offshore banks. Given the decline in French landings in recent years, and that the distribution has contracted (or shifted) to deeper waters, this species is assessed as Vulnerable in the Northeast Atlantic, on the basis of continuing population declines of at least 30%. Globally, L. circularis is assessed as Vulnerable, although with further data from the Northeast Atlantic it may prove to meet the criteria for a higher category. Close monitoring is required and future analyses should examine the long-term distribution and relative abundance of this species.
|Range Description:||Northeast and eastern central Atlantic, from northern Morocco northwards to Scotland, Iceland, southern Norway and northern part of North Sea and Skagerrak.
Mediterranean Sea: Western Mediterranean to Libya and absent from the Black Sea. Countries of occurrence include: Albania, Algeria, Croatia, France, Italy, Greece, Montenegro, Morocco, Slovenia, Spain and Turkey (Stehmann and Bürkel 1984, Bauchot 1987, Notarbartolo di Sciara and Bianchi 1998, Serena 2005).
Native:Albania; Algeria; Croatia; Egypt; France; Greece; Italy; Montenegro; Morocco; Norway; Portugal; Slovenia; Spain; Tunisia; Turkey; United Kingdom (Great Britain, Northern Ireland)
|FAO Marine Fishing Areas:||
Atlantic – northeast; Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
Leucoraja circularis is comparatively rare in the Northeast Atlantic. Accurate determination of abundance trends are not possible, as most earlier surveys have focused on shelf fishing grounds, with no long-term, standardised surveys sampling off the edge of the continental shelf. Nevertheless, French landings data for this species have declined from about 500 tonnes per year in the early 1990s to about 300 tonnes per year. Species-specific landings data prior to this are not available. Trends in surveys are difficult to determine accurately due in part to limited time-series data for this species, and given some uncertainty in the taxonomic identification in earlier surveys. English (Cefas) surveys in the North Sea and Celtic Sea have not recorded this species since 1996 and 1997 respectively, though Scottish (FRS) surveys continue to record sandy ray in various surveys around Scotland. Given the low numbers caught in surveys in offshore shelf habitats, it is possible that the main part of the distribution is now in deeper water, such as along the edge of the continental shelf. Indeed, most of the recent captures of this species in Scottish surveys have been made in waters of 180–500 m depth. Given the decline in French landings in recent years, and that the distribution has contracted (or shifted) to deeper waters, it is assumed that the population has declined in the Northeast Atlantic. However, there is uncertainty in the magnitude of the decline in abundance for the population as a whole.
The Mediterranean International Trawl Surveys (MEDITS) covers the north Mediterranean coast, almost continuously, from west Morocco and Spain in the west Mediterranean to the Aegean Sea in the eastern Mediterranean (Baino et al. 2001). Six trawl surveys are carried out each year in the coastal areas of four arbitrary geographically defined areas: Western (Morocco, Spain, France), Western Central (Tyrrhenian, Corsican, Sardinia and Sicily coasts), Eastern Central (Adriatic, Ionian and Albanian coasts) and the Eastern (Aegean Sea). A total of 6,336 tows have been performed between 1994 and 1999 in depths ranging from 10 to 800 m. The Sandy Ray was recorded in only 12 hauls in the western area (Baino et al. 2001). The evidence that this species may now only be found in the western area of the Mediterranean points to a substantial reduction in area of occurrence of this species. Its depth range also appears to have contracted as it was previously found on shelf and slope bottoms between 70 and 275 m, mainly at around 100 m, but now it is found only in deeper waters between 500 to 800 m (Baino et al. 2001). The overall biomass index assessed through MEDITS in the west, north and eastern Mediterranean was 0.1kg/km² (Baino et al. 2001).
The occurrence of Sandy Ray in the Mediterranean appears to have decreased significantly in the last 50 years. Leucoraja circularis was present in both shelf and slope trawl surveys of the Gulf of Lions in 1957–1960 but is now absent from more recent comparable surveys. Between 1957 and 1960 the Sandy Ray was captured in >10% of hauls in shelf surveys and in approximately 17% of hauls in slope surveys. Whereas between 1966 and 1995 it was not recorded at all from 1,295 hauls in eight trawl surveys (Aldebert 1997).
In the south Ligurian and north Thyrrenian seas this species can be considered rare based on capture rates, from 1985–2005 only 10 specimens were caught in the bathyal zone (352–566 m of depth). The size range was 26–91 cm in total length (Serena et al. 2005).
|Habitat and Ecology:||
Benthic in offshore shelf waters and on upper slopes, in waters of 50–800 m depth. Traditionally, it was thought to be found mainly around 100 m depth on sandy and muddy bottoms, though it has been suggested that it is now more abundant in deeper waters. For example, within the Mediterranean, L. circularis was previously found on shelf and slope bottoms between 70 and 275 m (mainly at around 100m) but now it is found in deeper waters between 500 and 800 m (Baino et al. 2001).
Reproduction is oviparous with eggcases 90 x 50 mm (Stehmann and Bürkel 1984). The spawning period is undefined (Bauchot 1987, Notarbartolo di Sciara and Bianchi 1998). The size at maturity of males is 70–80 cm in the Mediterranean (N. Ungaro pers. comm.) and the maximum recorded size is 120 cm (Serena 2005). This species is piscivorous, feeding on a variety of fishes, including both teleosts (Angulliformes Clopsis bicolor, Osteichthyes n.d) and chondrichthyans (Etmopterus spinax, Galeus melastomus) (Vannucci 2005). Age at maturity, longevity, size at birth, reproductive age, gestation time, reproductive periodicity, fecundity, rate of population increase and natural mortality are unknown.
This species is a bycatch in mixed trawl fisheries operating in the outer parts and edge of the continental shelf. It may also be taken as a bycatch in gillnet fisheries targeting anglerfish and longline fisheries targeting hake, though information on the catches in these fisheries are poor. The potential threat of deepwater fisheries within the deeper part of the species range is also a possible cause for concern. The relatively large body-size (120 cm) would also indicate that this species is vulnerable to over-fishing. Due to its offshore habitat, it is of no importance to recreational fisheries.
This species is of local fishery importance (Serena 2005). The sandy ray in the Mediterranean is captured as bycatch of multi-species trawl fisheries and offshore bottom longlines. Benthic trawl effort has increased both numerically and in technological terms in the shelf and slope area of the Mediterranean over the last 50 years. For example, the Gulf of Lions area was initially exploited by small-scale benthic trawl fisheries comprising 27 small low powered boats with a total nominal horse power of 2,700 hp; more recently effort has increased to a total of 19,940 hp (1974–1987). Since then half of the fishing effort has been displaced to targeting small pelagic fish (Aldebert 1997). The Adriatic Sea is subject to trawling mainly by Italian, Croatian, Slovenian, and Albanian fleets, however, no landings data are available (Jukic-Peladic et al. 2001). Although little is known of the life history we can presume from similar species that it will have slow growth, low fecundity and large size of juveniles making it especially vulnerable to fishing exploitation (Brander 1981, Walker and Hislop 1998, Dulvy et al. 2000, Dulvy and Reynolds 2002). Moreover, although only large individuals may be landed for consumption, most size classes, including the eggcases, are taken in fishing nets as the legal mesh size used in much of the Mediterranean is approximately 20 mm (and eggcases reach 90 x 50 mm (Stehmann and Bürkel 1984)). The full retention of the cod end of the currently used gear types and the 20 mm mesh size commonly used in the Mediterranean mean that all life stages of this species are fished.
The potential threat of development of deepwater fisheries within this species is range is a possible cause for concern in the future. Although the General Fisheries Commission for the Mediterranean (GFCM), the main intergovernmental decision-making body on fishery management in the Mediterranean, has made the decision to refrain from expanding deep water fishing operations beyond the limit of 1,000 m, this species is not known to occur below 800 m. For more information, see: iucn.org/places/medoffice/documentos/deepsea_en.pdf.
Though there are no species-specific management measures for this species, there is a TAC for skates and rays in the North Sea and adjacent waters, and they may benefit from more generic management measures for demersal fisheries (e.g., mesh size regulations, effort reduction).
Future analyses should examine the long-term distribution and relative abundance of this species (ICES 2007). In the first instance, data on the occurrence of this species should be collated to enable this (ICES 2007). Appropriate non-trawling areas should be defined to protect a proportion of both the adult population and this skate’s eggs (which are often found in the trawl cod-end) (Ragonese et al. 2003).
|Citation:||Ungaro, N., Serena, F., Ellis, J., Dulvy, N., Tinti, F., Bertozzi, M., Mancusi, C. & Notarbartolo di Sciara, G. 2009. Leucoraja circularis. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 23 May 2013.|
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