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Bathyraja violacea 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Arhynchobatidae

Scientific Name: Bathyraja violacea (Suvorov, 1935)
Common Name(s):
English Okhotsk Skate
Synonym(s):
Raja violacea Suvorov, 1935
Taxonomic Notes: Some authors (Dolganov and Tuponogov 1999) suggest B. trachouros and B. violacea may be synonymous.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2009
Date Assessed: 2007-07-08
Annotations:
Needs updating
Assessor(s): Davis, C.D., Ebert, D.A. & Orlov, A.M.
Reviewer(s): Valenti, S.V. & Musick, J.A. (Shark Red List Authority)
Justification:
The Okhotsk Skate (Bathyraja violacea) is found in the north Pacific, in the Bering Sea, Commander and Kuril Islands to Hokkaido and Sea of Okhotsk. Although occasionally reported from Alaskan waters of the eastern Bering Sea slope, it was not recorded in recent surveys there. It inhabits the continental shelf and slope waters within the depth range 43–1,110 m; however the majority of the population occurs above 600 m. Biomass estimates from trawl surveys suggest that this is the sixth most abundant skate in Russian waters, but very few data are available to determine population trends over time. Fisheries operate throughout the entire range of this species and it is a bycatch species of bottom trawl fisheries for groundfish and gillnet fisheries for Greenland Halibut (Reinhardtius hippoglossoides), operating to 650 m depth. Given that the majority of this species’ population lies entirely within the range of fisheries, further investigation is required into catch levels and population trends. Insufficient information is currently available to assess the species beyond Data Deficient and it is recommended that this assessment be revisited in the near term.

Geographic Range [top]

Range Description:North Pacific: the Okhotsk Skate occurs off Russia and Japan, in the Bering Sea and Pacific Ocean from the Commander and Kuril Islands to Hokkaido and Sea of Okhotsk. The species has also occasionally been reported from the eastern Bering Sea slope in Alaskan waters (Mecklenburg et al. 2002), although recent surveys (1999–2004) have not recorded it (Stevenson et al. 2008).
Countries occurrence:
Native:
Japan; Russian Federation
FAO Marine Fishing Areas:
Native:
Pacific – northwest
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This is the sixth most abundant skate species in Russian waters (Dolganov 1999). This species is common in the Sea of Okhotsk and the northern Kuril Islands and eastern Kamchatka (A. Orlov pers. obs. 2007). The mean total biomass estimate for this species during bottom trawl surveys conducted in Russian waters during 1977–1999 was 60,800 mt; comprising 17,300 t in the Bering Sea, 7,400 t off Kuril Islands and Kamchatka, and 36,100 t in the Sea of Okhotsk (Dolganov 1999). Few data are available on historical trends. CPUE data from 1999–2000 showed a gradual decreasing trend (Orlov et al. 2006), but there have been no further surveys in recent years.

It is not common in the eastern Bering Sea or the Aleutian islands, where it is only occasionally encountered by surveys (D. Ebert pers. obs. 2007).
Current Population Trend:Unknown
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Okhotsk Skate inhabit continental shelf and slope waters within the depth range 43–1,110 m on sandy-gravel, sandy and muddy-pebbly substrates, although the majority of the population occurs above 600 m (Orlov et al. 2006, Dolganov 1998a). Preferred bottom temperatures ranged from -0.9 to 4.2°C (mean 2.42°C) and most skates occur within 3–3.5°C (Dolganov 1999, Orlov et al. 2006). Females mature at 5–6 years of age and 61.2–76.4 cm total length (TL) and males mature at 4–6 years of age and 53.9–73.2 cm TL (Dolganov 1998c). The species attains a maximum size of 107 cm TL and is estimated to live for nine years (Dolganov 2005). Size at birth is unknown but egg capsules measured 7–13.2 cm x 5.5–8.6 cm (Dolganov 1998c). Dolganov (1998c) suggested that reproduction takes place year-round, and females have been observed to deposit egg cases in December at depths of 300m (Orlov and Biryukov 2005). Feeds mostly on crustaceans, cephalopods and fishes (Dolganov 1998b, Orlov 1998, Chuchukalo and Napazakov 2002).
Systems:Marine

Threats [top]

Major Threat(s): Fisheries operate throughout the entire range of this species and it is a bycatch of bottom trawl fisheries for groundfish and gillnet fisheries for Greenland halibut. It is discarded, but post-discard survival may be low. In Russian waters, the Greenland halibut fishery usually operates down to 650m but most bottom trawl fisheries operate down to 450 m (A. Orlov pers. comm. 2007). Therefore, as the majority of this species’ population is distributed above 600m, it occurs primarily within the depth range of fisheries throughout its entire range. Bycatch rates for this species are low, compared to other more common skate species in the region, such as Alaska Skate (Bathyraja parmifera), Aleutian Skate (Bathyraja aleutica) and Whiteblotched Skate (Bathyraja maculata) (A. Orlov pers. obs. 2007).

Conservation Actions [top]

Conservation Actions: There are no conservation measures in place for this species. Assessment of catches and population trends is a priority and further surveys would provide species-specific data.

Citation: Davis, C.D., Ebert, D.A. & Orlov, A.M. 2009. Bathyraja violacea. The IUCN Red List of Threatened Species 2009: e.T161594A5460136. . Downloaded on 15 October 2018.
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