|Scientific Name:||Bathyraja richardsoni (Garrick, 1961)|
Raja richardsoni Garrick, 1961
|Taxonomic Source(s):||Garrick, J.A.F. 1961. Studies on New Zealand Elasmobranchii. Part XIII. A new species of Raja from 1,300 fathoms. Transactions of the Royal Society of New Zealand 88: 743-748.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Kulka, D.W., Orlov, A. & Barker, A.S.|
|Reviewer(s):||Walls, R.H.L. & Kyne, P.M.|
|Facilitator/Compiler(s):||Kyne, P.M. & Walls, R.H.L.|
Richardson’s Skate (Bathyraja richardsoni) is a bathydemersal species that occurs on the continental slope, submarine rises, and deepwater plains at depths of 1,219−2,992 m. It is known from sporadic records across its global distribution, which indicates that it is widespread. Its deep bathydemersal range places it beyond the current range of most human threats, in particular deepwater fisheries. Given that this species is widespread, rarely caught in fisheries (which have also decreased effort in recent years), and occurs at depths beyond the reach of the main deepwater fisheries operating in its range, Richardson’s Skate is assessed as Least Concern. In the future, bycatch in deepwater fisheries should be monitored and managed, particularly if deepwater fisheries expand into its range.
|Previously published Red List assessments:|
|Range Description:||Richardson's Skate is likely globally distributed. In the Northwest Atlantic, records of this species occur from the southern Labrador Shelf, Canada, to the mid-Atlantic Bight. There are sporadic records of this species from a large area across the North Atlantic and it is suspected to be even more widespread than records currently indicate. In the Northeast Atlantic, it has been recorded from the northern Bay of Biscay, Rockall Trough, west of Scotland and Ireland, and the Mid-Atlantic Ridge (Stehmann and Merrett 2001, Orlov et al. 2006, Johnston et al. 2010, Ebert and Stehmann 2013). It has also been found off the Azores and in the Mid-Atlantic Ridge area (Orlov et al. 2006). In the southern hemisphere, Richardson's Skate is known from the South Tasman Rise, Tasmania, Australia (Last and Stevens 2009) and there is a single record (the holotype) known from off New Zealand (Garrick 1961), although it may be more widely distributed in this region at abyssal depths (Last and Stevens 2009).|
Native:Australia (Tasmania); Canada; France; New Zealand; Portugal (Azores); United States (Massachusetts, New Jersey)
|FAO Marine Fishing Areas:|
Atlantic – northwest; Atlantic – northeast; Indian Ocean – eastern; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Population size and parameters are unknown. The first Northwest Atlantic records taken on survey longlines between 1965 and 1967 comprised 18 mature specimens taken at depths between 1,370 and 2,360 m (Scott and Scott 1988). These constituted the only Northwest Atlantic records until 2003 when a mature male and a mature female were collected from the slope fishery north of the Grand Banks (D. Kulka, pers. obs., 2006).|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||This bathydemersal skate occurs on the continental slope, submarine rises, and deepwater plains at depths of 1,219−2,992 m (Ayling and Cox 1982, Ebert and Stehmann 2013). Richardson's Skate reaches a maximum size of 174 cm total length (TL) (Templeman 1973). Size at birth is 18.2−24.5 cm TL. The species is oviparous like other skates but nothing more is known of its biology at present.|
|Use and Trade:||This species is not known to be used or traded.|
This species' wide depth distribution and relatively wide geographic range may offer refuge from fishing pressure. Incidental catch in deepwater longline and trawl fisheries is the main potential threat to Richardson's Skate in the North Atlantic, and likely other parts of its range. However, much of the range of this species occurs well beyond most deepwater fisheries.
About 10 to 20% of the Northwest Atlantic slope is fished annually (D. Kulka, pers. obs., 2006), but the majority of this skate's distribution is considered to be outside the range of fishing pressure because it is rarely caught in the Northwest Atlantic where fishing nets are set at 1,500 m depths off Newfoundland (and more commonly at 700−1,200 m). While deepwater fisheries have decreased in effort gradually over the past decade (Dransfeld et al. 2013, STECF 2014), they should still be monitored in case of future expansion, which could pose a threat to this skate. Off Tasmania, Australia, this skate might have been taken by incidental capture in the South Tasman Rise Trawl Fishery when it was in operation. This fishery is currently closed to protect stocks of its target species, the Orange Roughy (Hoplostethus atlanticus) (Patterson and Mazur 2014). This situation should be monitored if this fishery reopens in the future.
In 1999, the European Union (EU) introduced a Total Allowable Catch (TAC) for skates and rays of 6,060 tonnes (t) for fisheries operating in the Norwegian Sea and North Sea (International Council for the Exploration of the Sea [ICES] Division IIa and Subarea IV) based on landing statistics from the previous five years. This TAC has been progressively reduced by 8−25% annually to the current level of 1,256 t. As part of the TAC, the bycatch quota for vessels over 15 meters was set at 25% of live weight of catch retained on board per trip. For much of this period (1999−2014), the TAC was higher than reported landings and therefore not effectively constraining catches. Skate and ray TACs were established for other EU waters in 2009, including the Skagerrak and Kattegat (ICES Division IIIa) and from the northwest coast of Scotland and North Ireland to Portuguese waters (ICES sub-areas VI−IX) and have also been gradually reduced since then.
No species-specific measures exist for Richardson's Skate. To prevent this species from moving out of the Least Concern category, deepwater fisheries operating close to its range should be monitored. In the event of deepwater fisheries expansion or the reopening of, for example, the South Tasman Rise Trawl Fishery, catch of this species ought to be monitored and this assessment may require updating.
|Citation:||Kulka, D.W., Orlov, A. & Barker, A.S. 2015. Bathyraja richardsoni. The IUCN Red List of Threatened Species 2015: e.T63127A70709214.Downloaded on 25 March 2018.|
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