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Rhinoraja macloviana 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Arhynchobatidae

Scientific Name: Rhinoraja macloviana (Norman, 1937)
Common Name(s):
English Patagonian Skate
Spanish Raya Espinosa
Synonym(s):
Bathyraja macloviana (Norman, 1937)
Raja macloviana Norman, 1937
Taxonomic Notes: Compagno (1999, 2005) reallocated this species from Bathyraja to the genus Rhinoraja but the validity of this move remains unconfirmed. Both are currently in use, until a definitive systematic revision of these genera is conducted; a revision is underway with the Ph.D. thesis of Jimena San Martin.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2007
Date Assessed: 2007-03-01
Annotations:
Needs updating
Assessor(s): McCormack, C., Lamilla, J., San Martín, M.J. & Stehmann, M.
Reviewer(s): Kyne, P.M. & Valenti, S.V. (Shark Red List Authority)
Justification:
A poorly known medium-sized skate (to 77 cm TL) common in the Southwest Atlantic off Uruguay, Argentina and the Falkland/Malvinas Islands and in the Southeast Pacific off southern Chile. Known from depths of 53 m to 514 m. Reportedly taken as regular bycatch in deeper water benthic trawl fisheries targeting Merluccius hubbsi, M. australis and Dissostichus eleginoides off Argentina and Uruguay. There is no species-specific bycatch information available, however, fishing pressure off Argentina has increased substantially over the past decade and in 1999, there was a decrease in the captures of rays by the deep sea fishing fleet of around 15% with regard to 1998. There was a reported a decline in the biomass of B. macloviana captured during fishery-independent investigations at 45° to 55°S off Argentina from 1998 to 1999, however the second phase of investigations employed gear which likely reduced the capture of rays. The species comprises a small proportion of the catch of a longliner targeting Dipturus chilensis off Argentina. Also taken in the targeted multispecies skate fishery around the Falkland/Malvinas Islands. This fishery experienced dramatic declines in the early 1990s especially in the area south of the Islands. There is little species-specific information on population trends for B. macloviana, however, an assessment of the northern ray population did not indicate any significant trends in CPUE over the period from 1992 to 2001. Although more information is required on population trends, heavy fishing pressure has occurred in the past and is continuing throughout the species' range where other skates have undergone declines. Given that fishing pressure is intense and ongoing throughout the species' range and documented declines in overall skate captures, this species is assessed as Near Threatened on the basis of suspected past and future declines. There is concern that the species may be close to meeting the criteria for VU A4d.

Geographic Range [top]

Range Description:Widely distributed species within the Magellanic Province from 36°10' to 54°30'S and also in the Southeast Pacific off southern Chile (51°S).
Countries occurrence:
Native:
Argentina; Chile; Falkland Islands (Malvinas); Uruguay
FAO Marine Fishing Areas:
Native:
Atlantic – southwest; Pacific – southeast
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Population size unknown.
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Benthic species reported from 53 m to 514 m (J. Pompert pers. comm.) depth in a bottom temperature range of 3.5 to 7.3°C (Menni and Stehmann 2000).

Size at maturity has been estimated at 54.9 cm Total Length (TL) and 53 cm TL for females and males, respectively (Scenna 2003). Maximum size has been estimated at 77cm TL (Agnew et al. 2000). The smallest known specimen was 13 cm TL (Stehmann et al. unpubl. data).

Bathyraja macloviana is a specialist feeder on polychaetes and a small proportion of amphipods, isopods and decapods (Brickle et al. 2003). Like other skates, this species is oviparous.

Further information on the life history of the species may become available in the near future as the ECORAYA project is finalised (M. Stehmann pers. comm. 2006).
Systems:Marine

Threats [top]

Major Threat(s): Throughout this section the term rajid refers to skates of both the families Rajidae and Arhynchobatidae.

Argentina/Uruguay
Skate landings have been increasing considerably in Argentina due to international demand. Prior to 1994, skate captures were less than 1,000 t, however, since that year skate landings increased considerably, reaching >15,000 t in 2001 and 17,465 t in 2003 (Massa et al. 2004).

Bathyraja macloviana is a regular bycatch in bottom trawl fisheries for bony fishes. It has been captured during fishery-independent investigations for hake Merluccius hubbsi and other species (García de la Rosa et al. 2000). García de la Rosa et al. (2000) reported a 67% decline in the biomass of B. macloviana captured from 45° to 55°S during the summer investigations of 1999 compared to 1998, however, it was acknowledged that during the second phase of the investigations, new gear was employed which likely reduced the capture of rays. During 1999, there was a decrease in the captures of rays by the deep sea fishing fleet of around 15% with regard to 1998 (García de la Rosa et al. 2000).

The species is also landed very rarely in the Dipturus chilensis directed skate fishery off Argentina which currently comprises a single vessel. Onboard observation of the fishing operation in 2000 and 2001 indicated that the vessel fished from 37° to 44°S off Argentina in two regions; around 50m of depth and along the 100 m isobath (Colonello et al. 2002). Species-specific bycatch data remain a priority for this and the trawl fishery.

Falkland/Malvinas Islands
Since 1989, rajids have been targeted by a Korean fleet utilizing demersal trawls around the Falkland/Malvinas Islands. The fishery initially operated over two main areas, one located on the shelf edge to the north of the Islands, and the other to the south of the Islands. Following declines in the early 1990s, the southern area was closed to the fleet in 1996 and the fishery now concentrates in the northern area (north of 52°S). A recent assessment of the northern ray population, utilizing observer data, indicated no increasing or decreasing trend in CPUE for this species (Wakeford et al. 2004). There have been no assessments of the population south of the area since the closure however; this species may also be caught as bycatch by trawlers operating in the area.

Conservation Actions [top]

Conservation Actions: Argentina
There are theoretically TACs, minimum sizes and overall annual quotas for quite a number of elasmobranch species in Argentina, however, little attention is paid to these and there is no regular monitoring by authorities (M. Stehmann pers. obs. 2006). Species-specific assessments of direct and indirect catches are a priority.

Falkland/Malvinas Islands
The following information is taken from Agnew et al. (1999 and 2000) unless otherwise specified.

The Falkland/Malvinas Islands multispecies skate fishery is managed by limiting fishing effort. The effort that each vessel is likely to exert is calculated (based on size, duration of license and past fishing history) and since 1994 only a limited number of licenses are granted to ensure that the total allowable effort (determined from assessments of stock status) is not exceeded. Stock status assessments are not, however, species-specific and a sustainable total allowable effort for the entire stock may not translate to sustainable levels of effort for individual species.

Following declines in CPUE in the early 1990s, in 1996, the southern area (below 52°S) was closed to rajid fishing and the fishery is now resticted to the area north of the Islands. This closure is extended to 50°30´S (between 56°30W and 58°W) during the second season of each year to exclude the skate fishing fleet from Loligo gahi fishing grounds. All licensed vessels are required to provide daily catch and effort details, including discards of commercial and non-commercial species to the Falkland Island Fisheries Department. There is, however, no requirement to report species-specific information. Scientific observers are deployed onboard skate vessels in order to quantify the catch composition by species and to obtain detailed biological data on individual species.

Vessels fishing under general finfish licenses are prohibited from targeting rajids, although a small bycatch (below 10%) is allowed.

Citation: McCormack, C., Lamilla, J., San Martín, M.J. & Stehmann, M. 2007. Rhinoraja macloviana. The IUCN Red List of Threatened Species 2007: e.T63117A12612149. . Downloaded on 16 October 2018.
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