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Narcine bancroftii

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES NARCINIDAE

Scientific Name: Narcine bancroftii
Species Authority: (Griffith & Smith, 1834)
Common Name(s):
English Caribbean Electric Ray
Taxonomic Notes: Recent revisions have subdivided the previously wide-ranging Narcine brasiliensis into Narcine bancroftii (Griffith, 1834) which is widely distributed from North Carolina, USA, through parts of the Gulf of Mexico, the Caribbean Sea, the Greater Antilles, the Lesser Antilles and the northern coast of South America to northern Brazil and Narcine brasiliensis (Olfers, 1831) which is endemic to the Southwest Atlantic in Brazil, Uruguay and Argentina (Carvalho 1999).

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2abd+3bd+4bd ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor(s): Carvalho, M.R. de, McCord, M.E. & Myers, R.A.
Reviewer(s): Fowler, S.L. & Kyne, P.M. (Shark Red List Authority)
Justification:
Narcine bancroftii is a shallow water species found on soft substrates from the intertidal zone to a depth of 35 m. The species has a wide range in the Western Atlantic from North Carolina, through the Gulf of Mexico, the Caribbean, the Lesser and Greater Antilles and the north coast of South America to at least Maranhão in northern Brazil. The southern extent of its range is uncertain due to previous records representing the Southwest Atlantic endemic, N. brasiliensis. The species reaches ~60 cm TL, females are reported to have a fecundity up to ~20 pups, and the species is characterized by a very low age at maturity in females of two years. The species is captured as bycatch by inshore shrimp trawl and other fisheries. It does not appear to be utilized and is discarded at sea, but survivorship rates are thought to be very low. Furthermore, abortion of embryos by captured gravid females is of concern. While specific catch data are lacking over most of the species' range, declines to 2% (95% confidence intervals 0.5 to 5%) of its baseline abundance in 1972 have been demonstrated in the Northern Gulf of Mexico. Shrimp trawl fishing is intense in that area and while the implementation of Turtle Exclusion Devices and Bycatch Reduction Devices has lowed overall bycatch rates, these mitigation measures are thought to be ineffective for this species due to it size and sluggish swimming ability. Given the species' very low age at maturity it would take a very intense fishery to locally eliminate this species; however, this has been demonstrated in the Northern Gulf of Mexico. Further data showing declines of a similar magnitude are available from the US east coast and Florida. While specific data are lacking, fishing activities, both artisanal and commercial in nature are generally intense and most often unregulated in shallow inshore waters of the remainder of the species' range. Given that large declines have been documented in US waters where data are available, there is no reason to suspect that similar declines have not also occurred elsewhere across the species' range. The species is therefore globally assessed as Critically Endangered, based on observed declines in US waters and inferred declines throughout the rest of the species' range. Information from outside US waters is a priority.

Geographic Range [top]

Range Description: Wide distribution in the western Atlantic from North Carolina through parts of the Gulf of Mexico and the Caribbean and along the northern coast of South America. Occurs to at least the state of Maranhão in Brazil, but may also occur off northeastern Brazil. The exact distribution of Narcine species off northeastern Brazil is presently unresolved as N. bancroftii in Brazil was previously referred to as the "wide-ranging" N. brasiliensis. That species is a Southwest Atlantic endemic occurring off southern Brazil, Uruguay and Argentina and although its occurrence off northeastern Brazil is documented for the states of Paraíba and Pernambuco (R. Rosa pers. comm.) it is not certain whether records of N. brasiliensis from the State of Ceará truly represent that species or N. bancroftii. It is thought to exist in the Bahamas, however this is not confirmed.
Countries:
Native:
Brazil; French Guiana; Guyana; Suriname; United States (Florida, Mississippi, New Mexico, North Carolina); Venezuela, Bolivarian Republic of
FAO Marine Fishing Areas:
Native:
Atlantic – northwest; Atlantic – southwest; Atlantic – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Although this species exhibits an extensive distribution, taxonomic revision may result in subdivision of the species in the future, thereby restricting its range (Carvalho 1999a). This will lead to a subsequent decrease in population size.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Narcine bancroftii is a shallow water species found on soft substrates from the intertidal zone to a depth of 35 m. Both oviducts appear to be synchronous in adult females. A 47 cm TL female caught in Maranhão, Brazil, contained embryos which were aborted on landing on the vessel. Oviducts are very thin-walled, transparent and puncture easily. The smallest female containing embryos (aborted) was 36.0 cm TL (Carvalho 1999).
Systems: Marine

Threats [top]

Major Threat(s): Electric rays are sluggish swimmers, with small home ranges, highly localized within an area and concentrating in surf zones adjacent to barrier beaches and on offshore sand bars in warm months and moving offshore in winter (Rudloe 1989), making them susceptible to localized population depletion. The species is captured as bycatch by inshore shrimp trawl seining net fisheries. It does not appear to be utilized and is discarded, but survivorship rates are thought to be very low. Furthermore, gravid females of the species have been observed to abort embryos upon capture and so even if discarded individuals survive, reproductive output is reduced. While specific catch data are lacking over most of the species range, declines to 2% (95% confidence intervals 0.5 to 5%) of its baseline abundance in 1972 have been demonstrated in the Northern Gulf of Mexico, most probably caused by shrimp trawling (Shepherd and Myers 2005). Shrimp trawl fishing is intense in that area, particularly in shallow waters (thus coinciding with the bathymetric range of N. bancroftii), with 4 to 5 million trawl hours annually (Shepherd and Myers 2005). While data in Shepherd and Myers (2005) compared the time period 1972 to 2002, the actual severity of declines may have been underestimated as shrimp trawling began in the region during 1912 to 1915 (Shepherd and Myers 2005). Similar high rates of decline are seen in the US coastal areas between Cape Canaveral (Florida) and Cape Hatterus (North Carolina) in US trawl surveys between 1989 and 2001 (a decline to 5% during this period). Furthermore, similar rates of decline are seen between 1994 and 2004 from diver surveys (data from Reef Environmental Educational Foundation) in eastern Florida and the Florida Keys. These declines may not be representative of the entire range, but these are the only regions with reliable survey data, and should be representative of regions with similar fishing impact. While specific data are lacking, fishing activities, both artisanal and commercial in nature are generally intense and most often unregulated in shallow inshore waters of the remainder of the species' range. See Fowler et al. (2005) for regional and country overviews. Given that large declines have been documented in US waters where data are available, there is no reason to suspect that similar declines have not also occurred elsewhere across the species' range where fishing activities are intense and unregulated. Pollution and oil exploration may also adversely affect the habitat of N. bancroftii, although no specific information is available.

Conservation Actions [top]

Conservation Actions: There are no conservation measures directed at this species. While the implementation of Turtle Exclusion Devices and Bycatch Reduction Devices in shrimp trawl fisheries in the Northern Gulf of Mexico has lowed overall bycatch rates (for example see Steele et al. (2002), these mitigation measures are thought to be ineffective for this species due to it size and sluggish swimming ability. Details of bycatch in coastal fisheries throughout the rest of the species' range (i.e., outside of US waters) is required to determine the impact of fishing activities and allow for a more robust global assessment.

Citation: Carvalho, M.R. de, McCord, M.E. & Myers, R.A. 2007. Narcine bancroftii. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 02 September 2014.
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