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Atlantoraja platana

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES ARHYNCHOBATIDAE

Scientific Name: Atlantoraja platana
Species Authority: (Günther, 1880)
Common Name/s:
English La Plata Skate
Spanish Empalastro, Oscura, Platana, Raya, Raya Oscura

Assessment Information [top]

Red List Category & Criteria: Vulnerable A4bd ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Assessor/s: San Martín, J.M., Stehmann, M.F.W. & Kyne, P.M.
Reviewer/s: Notarbartolo di Sciara, G., Haywood, M. & Kulka, D. (Shark Red List Authority)
Justification:
A small (to ~60 cm total length) moderately rare (M.F.W. Stehmann pers. obs.) softnose skate endemic to the Southwest Atlantic off southern Brazil, Uruguay and Argentina (23° to 45°S). A continental shelf species recorded from depths of 19 to 181 m whose range is facing intensive fishing pressure. Demand for skates is increasing on an international scale, resulting in growing fishing pressure on skate species along coastal and continental shelf waters of Argentina and Uruguay. In these countries, Atlantoraja spp. are mainly taken as bycatch in coastal demersal multi-species fisheries. Since 2000, however, specific targeting of skates has occurred. Fishing pressure is also known to be intense across the species' range in southern Brazil, where demersal trawl fisheries operate and skates are landed as part of multi-species fisheries. Species-specific catch data are not available for A. platana, however, significant declines have been shown for both the similar-sized A. cyclophora and the larger A. castelnaui, both of which are sympatric with A. platana. Given heavy fishing pressure, increasing demand and documented declines, both A. castelnaui and A. cyclophora has been previously assessed as threatened species. As such, A. platana is assessed as Vulnerable as, while specific data are lacking, it is reasonable to assume that it too will have faced similar declines in the past and suspect that it will face similar declines in the future. Furthermore, it is apparently absent from localities where it previously occurred due to habitat degradation, mainly from pollution. Continued monitoring, species-specific catch data and improved management are urgently needed.

Geographic Range [top]

Range Description: A Southwest Atlantic endemic species, distributed from 23°S to 45°S.
Countries:
Native:
Argentina (Buenos Aires, Chubut, Rio Negro, Santa Cruz); Brazil (Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, São Paulo); Uruguay
FAO Marine Fishing Areas:
Native:
Atlantic – southwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Moderately rare skate (M.F.W. Stehmann pers. obs.) with patchy occurrence across its range. It is rare north of 26°S.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Benthic on clay, mud and sand substrates on the continental shelf at depths of 19 to 181 m (Menni and Stehmann 2000).

Females mature at 45 to 50 cm total length (TL) and males mature at 47 to 53 cm TL (M.F.W. Stehmann pers. obs., unpubl. ISH records ?W. Herwig' expeditions). The maximum recorded size for A. platana is 73.4 cm TL (Zaro 1979).

Like other skates, this species is oviparous. It has an annual reproductive cycle, with an egg-laying season from January to September, with a peak in January (Peres and Vooren 1993). Food includes fish, penaeid crustaceans and cephalopods (Peres and Vooren 1993).
Systems: Marine

Threats [top]

Major Threat(s): Trawl fishing along the distribution and in the habitat of this species is intense, while demand for skates is increasing in the international market. In the coastal and continental shelf waters of Argentina and Uruguay this has resulted in rising fishing pressure on all skate species. A. platana is taken mainly as bycatch in fisheries for coastal demersal species (multi-species fisheries) and in Argentina the Atlantoraja species has been known to be landed since 1994. There are only seven records of A. plantana from 1993 to 2005 on the Argentine shelf (A. Massa pers. comm.) however species specific data were not previously recorded. Since 2000, however, one vessel has been specifically targeting skates. For these fishing activities, species-specific landing statistics are generally unavailable as all species of batoids are recorded as ?unidentified rays and skates?. In Argentina, declared landings of skates and rays increased significantly during the 1990s from 910 MT in 1993 to 5,701.2 MT in 1994 and to 12,443.7 MT in 1996 (Chiaramonte 1998). Landings continue to rise and were 17,465 t in 2003 (Massa et al. 2004).

Fishing pressure is also known to be intense across the species' range in southern Brazil, where demersal trawl fisheries operate and skates are landed as part of multi-species fisheries. While species-specific data are required from southern Brazil, Amorim et al. (1997) stated that in the pink shrimp fishery off São Paulo, Brazil the catch per unit effort of discarded batoids (4.6 kg per hour) is approximately three times higher than that of the target species (1.4 kg per hour).

Perez and Wahrlich (2005) noted an overall discard rate of 69% for skates taken in the deepwater monkfish gillnet fishery off southern Brazil (between 22°´44 and 34°21´S). While, Atlantoraja castelnaui and A. cyclophora were identified amongst these skates, A. platana was not. Perez and Wahrlich (2005) surveyed between depths of 132 to 607 m and so the interaction of A. platana with this fishery is likely minimal.

Menni and Stehmann (2000) note that the species was historically recorded from Punta Lara, near La Plata in Argentina but that its more recent absence from this locality is likely due to pollution.

Conservation Actions [top]

Conservation Actions: No conservation measures exist in Brazil. In Argentina, the only management strategy for skates is an annual total catch for skates distributed in the coastal waters of Buenos Aires Province. For 2003 this was 4,000 MT. Continued monitoring, improved fisheries data collection and species-specific catch data are needed across the species' range. Given the increasing international demand for skate products, and increased exploitation in the Southwest Atlantic, trade management measures are also essential (Perez and Wahrlich 2005).
Citation: San Martín, J.M., Stehmann, M.F.W. & Kyne, P.M. 2007. Atlantoraja platana. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 19 April 2014.
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