|Scientific Name:||Discopyge tschudii|
|Species Authority:||Heckel, 1846|
|Infra-specific Taxa Assessed:|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Massa, A., Hozbor, N. & Lamilla, J.|
|Reviewer(s):||Kyne, P.M., Cavanagh, R.D., Fowler, S.L. & Musick, J.A. (Shark Red List Authority)|
Discopyge tschudii is a small temperate electric ray from the Southwest Atlantic and Southeast Pacific Oceans (occurring as two separate subpopulations). It is rare in southern Brazil where it occurs only in small numbers in winter and in Uruguay captures are also low. In Northern Argentina, biomass measured by research trawling decreased by 88% in the years 1994 to 1999. However, because there was an apparent change in the distribution pattern of the species it is impossible to tell whether this decline was caused by a reduction in population size or geographic availability of Discopyge mitigated by different hydrographic conditions. However, given this data and intense fishing pressure across its range in the Southwest Atlantic it is classified as Vulnerable there. Future research may result in downgrading the conservation status to Near Threatened or upgrading perhaps as high as Critically Endangered. In the Southeast Pacific there is no information on the impact of fisheries bycatch on its abundance and this population is assessed as Data Deficient. Globally, the species is assessed as Near Threatened, taking into account its threatened status in the Southwest Atlantic, where fisheries appear to have caused a rapid and steep population decline, and an inferred population decline in the Southeast Pacific as a result of bycatch mortality.
|Range Description:||Vooren and Betito (pers. com.) obtained D. tschudii off Brazil between 33°45' and 33°56'S at 27 to 35 m depth, with temperature ranging from 11.6 to 13.5°C and salinities from 32.3 to 33.0‰. This is a cold water species entering south Brazilian waters from the south in small numbers during winter, but not spreading farther north than 33°S (Menni and Stehmann 2000). In Uruguay, captures of this species are low (A. Domingo, pers. comm).|
Native:Argentina; Brazil; Chile; Peru; Uruguay
|FAO Marine Fishing Areas:|
Atlantic – southwest; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Given that the range does not extend further south beyond northern Argentina in the Atlantic we assume this species occurs as two separate subpopulations (Atlantic and Pacific coasts).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Reported from 22 to 181 m depth (Menni et al. 1981). Many aspects of the life history of D. tschudii are still unknown. D. tschudii feeds mainly on polychaete worms and gammarid amphipods (Menni and Stehmann 2000). It is an aplacental viviparous species (ovoviviparous) (Garcia 1984).
Size at maturity: Chile - unknown; Argentina - matures at 27.5 cm total length (TL) (females) and at 35 to 46 cm TL (males) (Garcia 1984).
Maximum size: Chile - females between 17.8 and 44.2 cm total length (TL), males between 21.9 and 53.8 cm TL (Pequeño et al. 1988); Argentina - females 39 cm TL, Males 54 cm TL (Garcia 1984).
Size at birth: Chile - unknown; Argentina - 8.5 to 9.2 cm TL (Garcia 1984).
Average annual fecundity or litter size: Chile - unknown; Argentina - 1 to 12 (mostly 4 to 5).
Caught as a bycatch of bottom trawl fisheries; though of low commercial value and is discarded or utilised for fish meal. Trawl fishing from southern Brazil to northern Argentina expanded rapidly over the last 10 years and continues unmanaged. Off Buenos Aires Province, Argentina and Uruguay, biomass measured by research trawling decreased by 88% in the years 1994-1999 (Hozbor and Massa, unpublished data). However because there was an apparent change in the distribution pattern of the species it is impossible to tell whether this decline was caused by a reduction in population size or geographic availability of Discopyge mitigated by different hydrographic conditions between these years. Trawl fishing in the habitat of the species is intense but there are no data available on catches. In Uruguay, captures of this species are generally low (A. Domingo, pers. comm.).
There is no specific information available on threats in the Southeast Pacific, but it is most definitely taken as bycatch in demersal fisheries in this region.
|Conservation Actions:||No conservation measure are in place for this species.|
Garcia, M.L. 1984. Sobre la biología de Discopyge tschudii (Chondrichthyes, Narcinidae). Physis A 42(103):101-112.
IUCN. 2004. 2004 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 23 November 2004.
IUCN SSC Shark Specialist Group. Specialist Group website. Available at: http://www.iucnssg.org/.
Menni, R.C. and Stehmann, M.F.W. 2000. Distribution, environment and biology of batoid fishes off Argentina, Uruguay and Brazil, a review. Revista del Museo Argentino de Ciencias Naturales (Nueva Serie) 2(1): 69-109.
Menni, R.C., López, H.L. and García, M.L. 1981. Lista comentada de las especies de peces colectadas durante la campaña V del B/I "Shinkai Maru" en el Mar Argentino. Contributions of the National Institute of Fishing Investigations 383: 267-280.
Pequeño, G., Navarro, R. and Oporto, J. 1998. Discopyge tschudii Heckel, 1845: aporte a su taxonomía, con hincapié en su dimorfismo sexual (Chondrichthyes, Narcinidae). Est. Oceanol. 7:41-50.
|Citation:||Massa, A., Hozbor, N. & Lamilla, J. 2004. Discopyge tschudii. The IUCN Red List of Threatened Species 2004: e.T44993A10961829.Downloaded on 25 August 2016.|