|Scientific Name:||Gymnura altavela (Linnaeus, 1758)|
|Red List Category & Criteria:||Vulnerable A2bd+4bd ver 3.1|
|Assessor(s):||Vooren, C.M., Piercy, A.N., Snelson Jr., F.F., Grubbs, R.D., Notarbartolo di Sciara, G. & Serena, S.|
|Reviewer(s):||Musick, J.A., Kyne, P.M., Cavanagh, R.D. & Valenti, S.V. (Shark Red List Authority)|
A wide-ranging butterfly ray from tropical and warm temperate continental shelf waters on the eastern (Portugal to Angola) and western (Massachusetts State, USA to Buenos Aires Province, Argentina) sides of the Atlantic Ocean, including the Mediterranean Sea, the Black Sea and the Madeira and Canary Islands. A large (to 220cm disc width) ray with a small litter size (producing 1-8 pups depending on geographic location), making it intrinsically vulnerable to population depletion. It has a patchy and discontinuous distribution and appears to be habitat-dependent. Noted for the quality of its meat and is landed for human consumption (Figueiredo 1977).
Gymnurids are susceptible to a variety of fishing gear and are commonly taken in inshore fisheries. Fishing pressure is intense throughout its coastal habitat in southern Brazil, where the species occurs all year round and breeds (Vooren 1997) and where it has been landed commercially since at least 1986 (Araujo and Vooren 1986). Occurred in beach-seine catches in the 1980s, but had disappeared from catches in 2002 and 2003 (Vooren and Lamónaca unpublished data). Trawl catch rates in kg/h in coastal waters of southern Brazil declined by ~99% between 1982 and 2005. The species was common and abundant in 1982, but was caught only sporadically in 2005, when all captured specimens were small juveniles (Naves and Vooren 2001, Vooren et al. 2005). Coastal fishing pressure is intense in other parts of its range in the Southwest Atlantic and it is inferred to have undergone similar declines elsewhere. Given observed and inferred declines, the exposure of its shallow coastal habitat to trawl fishing, its vulnerable life-history characteristics, patchy distribution, and continuing intense fishing pressure, this species is assessed as Critically Endangered in the Southwest Atlantic.
Gymnura altavela has a very patchy distribution in US waters, where it can be locally abundant (i.e. adults are in the mouths of tidal creeks along the Virginia coast) and appears to be habitat dependent. It is rarely taken as bycatch and is not commercially targeted in U.S. waters, and fishery-independent longline surveys show no trends in catch rates over the period 1996 to 2003. In the absence of significant threats to the species in US waters, the species is assessed as Least Concern for the USA.
This species was not uncommon in the catch of demersal fisheries (trawl and set nets) throughout the Mediterranean and the southern shores in particular. Although previously quite frequently captured in the Sicilian Channel, it is now absent from the local catch record (M. Vacchi, pers. comm.), and from the whole of the Mediterranean International Trawl Survey (MEDITS) records (i.e., since 1994). Only occasional specimens have been caught in demersal fisheries to testify that it is not extirpated from the region. Given that its occurrence in the Mediterranean today is so rare (despite some comprehensive survey work throughout its historical range) it must have declined massively in the past 20 years, and since its previously known habitat and area of occurrence continue to face fishing pressure and degradation from coastal development, this species is assessed as Critically Endangered in the Mediterranean on the basis of a suspected past decline of >80%.
In the Eastern Atlantic, where G. altavela was formerly common all along the west African coast, it has been taken by the rhinobatid artisanal fishery using large mesh bottom gillnets, and in other artisanal landings. Although large individuals are still landed sometimes from Mauritania south to Guinea, artisanal fishers and other observers indicate that the abundance has declined severely and that the median size has been dramatically reduced as most of the adults have been removed by fishing activities (Ducrocq, M. pers. comm). Even in the Banc d'Arguin National Park, Mauritania, where it is normally fully protected, incidental catches consist of more than 90% juveniles and subadults while large individuals were common in the 1980s (Ducrocq, M. pers. comm). Pregnant females observed in landings of artisanal coastal fisheries in Mauritania, Senegal and Guinea-Bissau, suggest that pupping occurs in shallow coastal waters, where the fishing pressure is intense and unlikely to reduce in the future (Camara et al. in prep.). This species is assessed as Vulnerable on the basis of a suspected continuing decline of at least 30%.
Globally, the extent of demonstrated declines in the Southwest Atlantic, Mediterranean and West Africa is considered to meet the criteria for Vulnerable, based on an overall past and suspected continuing decline of >30%. Species specific monitoring, and urgent protection in areas where it is threatened are needed.
|Range Description:||Patchily distributed in tropical and warm temperate continental shelf waters on the eastern (Portugal to Ambriz, Angola) and western (from Massachusetts State, USA (42°N) to Buenos Aires Province, Argentina (~38°S)) sides of the Atlantic Ocean, including the Mediterranean Sea, the Black Sea and the Madeira and Canary Islands (McEachran and Fechhelm 1998). Rarely reported from the Gulf of Mexico (McEachran and Carvalho 2002). It has a very patchy distribution in the Northwest and Western Atlantic, where it can be locally abundant and appears to be habitat dependent. Adults are common in the mouths of tidal creeks along the Virginia coast, USA (Musick et al. unpublished data). In the 1980s Gymnura altavela was common and abundant throughout the year on the continental shelf of southern Brazil at depths of 10 to 150 m, being classified as a breeding resident species (Vooren 1997).|
Native:Albania; Algeria; Angola; Argentina; Belize; Benin; Bosnia and Herzegovina; Brazil; Cameroon; Colombia; Costa Rica; Côte d'Ivoire; Croatia; Cyprus; Egypt; Equatorial Guinea; France; French Guiana; Gabon; Gambia; Ghana; Greece; Guinea-Bissau; Guyana; Honduras; Israel; Italy; Lebanon; Liberia; Libya; Malta; Mauritania; Mexico; Monaco; Morocco; Nicaragua; Nigeria; Panama; Portugal; Senegal; Sierra Leone; Slovenia; Spain (Canary Is.); Suriname; Syrian Arab Republic; Togo; Tunisia; Turkey; United States; Uruguay; Venezuela, Bolivarian Republic of; Western Sahara
|FAO Marine Fishing Areas:|
Atlantic – northwest; Atlantic – western central; Atlantic – northeast; Atlantic – eastern central; Atlantic – southeast; Atlantic – southwest; Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is taken annually in the VIMS longline survey at a single site during the summer months, but no population trends are evident from 1996 to 2003 (Musick et al. unpub. data). Historically, Gymnura altavela was not uncommon in the catch of demersal fisheries (trawl and set nets) throughout the Mediterranean and the southern shores in particular. However, it is absent from the whole of the Mediterranean International Trawl Survey (MEDITS) records (i.e., since 1994) and it is only the occasional specimens that have been caught in demersal fisheries that testify the species is not extirpated from the region. In southern Brazil it disappeared from beach-seine catches in 2002 to 2003, where it had been historically observed in the 1980s. Also in southern Brazil at latitudes 29°20'S to 33°40'S and depths 10 to 20 m, trawl survey catch rates standardized for groundrope length, and frequency of occurrence, were 16.0 kg/h and 54% in January 1982 (20 trawl hauls), and 0.2 kg/h and 8% in February 2005 (62 trawl hauls). The catches in 2005 were of small juveniles, indicating that reproduction still takes place in that area (Naves and Vooren 2001, Vooren et al. 2005). The shallow waters of the Banc D'arguin in Mauritania may be a pupping ground (Camara et. al. in prep).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||A large, locally abundant, but overall unabundant, inshore batoid with a patchy and discontinuous distribution, found in shallow coastal waters over sand and mud generally to depths of 50 to 55 m (Bini 1967, McEachran and Felchman 1998), although it has been recorded from depths of 10 to 150 m off southern Brazil (Vooren 1997).
Little is known of its biology. Maximum size is reported as 220 cm disc width (Musick et al. unpub. data) in the Northwest Atlantic; sizes exceeding 400 cm DW reported off the coast of West Africa (Bini 1967) may be erroneous. Size at maturity is reported as 155 cm DW in males and 102 cm DW in females (Daiber and Booth 1960). Aplacental yolksac viviparous reproduction with litter size varying from 2 to 8 depending on geographic location (four pups/litter reported by Bigelow and Schroeder (1953) and Bini (1967); 2-6 by Capapé et al. (1992) and 1-3 by Tortonese (1956) for the Mediterranean; up to five per litter in southern Brazil (Vooren unpub. data); and, up to eight by Musick et. al. (unpub. data) for the Northwest Atlantic). Reproduces annually and gestation time is reported as 4 to 9 months (Capapé et al. 1992).
Size at birth is reported as 38 to 44 cm DW (Bigelow and Schroeder 1953, McEachran and Carvalho 2002). Age at maturity, longevity, average reproductive age, annual rate of population increase and natural mortality are all unknown.
Coastal species are the most important commercial elasmobranchs in the Southwest Atlantic and fishing pressure is intense throughout the relatively shallow habitat of G. altavela (Bonfil et. al. 2005). Skate and ray landings in the artisanal fishery of Rio Grande do Sul, southern Brazil have declined dramatically since the early 1950s (Klippel et. al. 2005).
This species is taken by demersal multispecies trawl, beach-seine and recreational fisheries in southern Brazil (Vooren et al. 2005). It is noted as a good food fish Figueiredo (1977) and has been landed commercially in southern Brazil from at least 1986 onwards (Araujo and Vooren 1989). The species was frequently observed in beach-seine catches in the 1980s, but had disappeared from these catches in 2002 and 2003 (Vooren and Lamónaca unpublished data), and only occurred sporadically in trawl landings in 2002 and 2003. Also in southern Brazil at latitudes 29°20'S to 33°40'S and depths 10 to 20 m, trawl survey catch rates standardized for groundrope length, and frequency of occurrence, were 16.0 kg/h and 54% in January 1982 (20 trawl hauls), and 0.2 kg/h and 8% in February 2005 (62 trawl hauls) (Naves and Vooren 2001, Vooren et al. 2005). This strong decline in abundance is attributed to intense trawl fishing all year round in coastal waters. The catches in 2005 were of small juveniles, which is evidence that reproduction still takes place in that area (Klippel et al. 2005, Vooren et al. 2005). Intense coastal fishing pressure is continuing throughout its coastal range and the threat is ongoing. The exposure of its coastal habitat to fisheries and its vulnerable life-history characteristics provide little capacity for recovery.
Coastal fishing pressure is also known to be intense in Argentina, at the southern limit of this species' distribution. This species has occasionally been reported in catches along the coast of Argentina from Rio de la Plata to Quequén and has been reported as irregular in the demersal catches at Mar del Plata (Menni and Stehmann 2000). Batoids are an important resource in most demersal trawl fisheries in Argentina (Tamini et al. 2006). A coastal multispecies demersal trawl fishery operates out off Quequén (38°37'S, 58°50'S), in which bycatch of batoids fluctuates seasonally between 44.5% and 67.5% of total catch (Tamini et al. 2006). This species was not reported in a recent study of the bycatch of this fishery (Tamini et al. 2006), and a lack of historical information prevents a comparison of temporal trends.
The disappearance of this species from beach-seine catches in southern Brazil 2002 to 2003, where it was previously captured, and the decline of 99% in abundance since 1982 observed in those coastal waters warrant an assessment of Critically Endangered. Fishing pressure is intense throughout its range and it is likely that similar declines have occurred in areas where data are lacking.
This species is rarely taken as bycatch and is not commercially targeted in U.S. waters. Data sets from the coastal bottom longline shark fishery, the drift gillnet fishery, and fishery independent sampling (longline) by Virginia Institute of Marine Biology (VIMS) all show very low catch rates and no population trends are evident (Burgess et al. unpublished data, Carlson pers. comm., Musick et al. unpublished data). The occurrence of G. altavela appears to be habitat dependent, with all of the VIMS specimens caught at one station. This may explain its low abundance. It has a relatively wide occurrence on the US eastern seaboard and is only a minimal capture in fisheries in this region.
Historically this species was not uncommon in the catch of demersal fisheries (trawl and set nets) throughout the Mediterranean and the southern shores in particular. In the 1980s it was quite frequently captured in the Sicilian Channel and landed in Mazzara del Vallo (Trapani, Sicily), but now it is absent from the local catch record (M. Vacchi pers. comm). There are no records of G. altavela from the whole of the Mediterranean International Trawl Surveys (MEDITS), i.e., since 1994, indicating that it is perhaps absent from most of its former range in the Mediterranean. Occasional specimens turn up serendipitously in the catch of demersal fisheries, for example one adult male was captured in recent years near Anzio, Italy, now deposited in the collection of the University of Naples (Psomadakis et al. 2005) and one specimen captured in the Southern Adriatic in 2000 (Dulčić et al. 2003) thus testifying that the species is not extirpated from the region. However, its occurrence today is so rare that it must have massively declined in the past 20 years.
Benthic trawl effort has increased both numerically and in terms of technology in the shelf and slope areas 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 (total nominal horse power of 2,700 hp), but more recently effort has increased to a total nominal horse power of 19,940 hp (1974 to 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, Croation, Slovenian, and Albanian fleets, however, no landings data are available (Jukic-Peladic et al. 2001). Coastal development, pollution and anthropogenic disturbance through tourism activities are also a threat to its shallow coastal habitat in the Mediterranean.
Formerly common all along the west African coast, this species has suffered from fishing pressure, taken as bycatch in shrimp trawls and in artisanal fisheries. Targeted among other benthic sharks and rays, and caught in large mesh benthic gillnets targeting guitarfishes, shrimp trawls and various other benthic gear such as longlines and handlines. There is heavy fishing pressure throughout this species' inshore and shallow water habitat that is unlikely to be reduced in the coming years (M. Ducrocq pers. obs). Although large individuals are still landed sometimes from Mauritania south to Guinea, artisanal fishers and other observers indicate that the abundance has dropped severely and that the median size has been dramatically reduced as most of the adults have been removed by fishing activities (M. Ducrocq pers. obs). Even in the Banc d'Arguin National Park, Mauritania, where it is normally fully protected, the incidental captures consist of more than 90% juveniles and subadults while large individuals were common in the 1980s (M. Ducrocq pers. obs). Pregnant females have been observed in the landings of artisanal coastal fisheries in Mauritania, Senegal and Guinea-Bissau, suggesting that this species is giving birth in coastal shallow waters, where the fishing pressure is intense and is unlikely to reduce in the coming years (M. Ducrocq pers. obs).
|Conservation Actions:||No species specific management or protection is currently in place for this species, except for in the Banc D'arguin National Park, Mauritania where it is protected.|
|Citation:||Vooren, C.M., Piercy, A.N., Snelson Jr., F.F., Grubbs, R.D., Notarbartolo di Sciara, G. & Serena, S. 2007. Gymnura altavela. The IUCN Red List of Threatened Species 2007: e.T63153A12624290.Downloaded on 24 November 2017.|
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