|Scientific Name:||Bathyraja lindbergi Ishiyama & Ishihara, 1977|
|Taxonomic Source(s):||Eschmeyer, W.N. and Fricke, R. (eds). 2015. Catalog of Fishes: genera, species, references. Updated 1 October 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 1 October 2015).|
|Taxonomic Notes:||This species was first described from the Bering Sea (57°47'N, 173°47'W) by Ishiyama and Ishihara (1977). Subsequent Russian authors have considered this species a junior synonym of Bathyraja matsubarai (Sheiko and Fedorov 2000, Dolganov and Tuponogov 1999, Mecklenburg et al. 2002). However, recent Russian literature (e.g. Grigorov and Orlov 2013), and other authors, have considered B. lindbergi to be a valid species (Compagno 1999, Compagno 2005). Information from Alaska appears to pertain only to B. lindbergi. Bathyraja lindbergi and B. matsubarai are very similar and further taxonomic study is required on both species.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Ormseth, O.A., Foy, R., Davis, C.D., Ebert, D.A. & Orlov, A.|
|Reviewer(s):||Chabot, C.L. & Lawson, J.|
|Facilitator/Compiler(s):||Dulvy, N.K. & Walls, R.H.L.|
The Commander Skate (Bathyraja lindbergi) occupies the deep waters (126-1,193 m depth) of the Bering Sea and the Gulf of Alaska. It is a medium-sized species (maximum total length 102 cm) that is long-lived and late-maturing (maximum observed age = 35 years; age at 50% maturity = 21 years). Its life history strategy gives it the potential to be vulnerable to commercial fishing activity and other impacts, but population biomass is estimated to be stable in the eastern Bering Sea, and this species was assessed as Least Concern in the coastal waters of the Russian Federation. This species occurs at depths below those where most fishing activity takes places (~300 m and above), and there are no known habitat impacts such as pollution or development. Given this information, and that this species is managed as part of the Bering Sea/Aleutian Islands skate stock complex in Alaska, the Commander Skate is assessed as Least Concern. Either a shift to fishing in deeper waters or the development of a targeted fishery have the greatest potential to threaten the status of this species.
|Previously published Red List assessments:|
The Commander Skate inhabits the upper continental slope in the eastern Bering Sea (EBS) and western Bering Sea (WBS), in the Aleutian Islands (AI) and the Commander Islands (CI). It has been observed in the Gulf of Alaska (GOA) all the way to the Alexander Archipelago in Southeast Alaska, but it appears to be less common there. Reported depth ranges are from 126 to 1,193 m (Ishiyama and Ishihara 1977, Stevenson et al. 2007, Stevenson et al. 2008).
Native:Russian Federation (Kamchatka); United States (Alaska, Aleutian Is.)
|FAO Marine Fishing Areas:|
Pacific – northwest; Pacific – northeast
|Range Map:||Click here to open the map viewer and explore range.|
Recent population data exist only for the eastern Bering Sea (EBS) and are based on bottom trawl surveys conducted by the U.S. National Marine Fisheries Service. Between 2002 and 2012 the estimates of population biomass appeared stable, fluctuating between 3,393 t in 2010 and 4,378 t in 2012 (Ormseth 2014). The coefficient of variation (CV) ranged from 13-16%, indicating a moderate level of uncertainty in the biomass estimates. The CV is consistent with the ubiquity of the Commander Skate in EBS slope survey catches. In 2012 this species was the fourth-most abundant skate species on the EBS slope (Ormseth 2014).
|Current Population Trend:||Stable|
|Habitat and Ecology:|
The Commander Skate has a reported depth range of 126 to 1,193 m, but it is likely that this species prefers a narrower range. In the EBS, it appears to be limited to depths between 400 m and 1,000 m, with the highest relative abundance between 800 m and 1,000 m (Stevenson et al. 2008). Other species of skate on the EBS slope use small, discrete areas on the upper slope (145-380 m depth) as nursery areas where they deposit embryos in eggcases (Hoff 2010). It is unknown whether the Commander Skate has similar nursery areas or where these might be located. Similarly, the known depth distribution in the EBS is derived only from summer surveys, and seasonal movements are not known.
This is a medium-sized skate, with a maximum observed length of 102 cm TL (Stevenson et al. 2007). The maximum age is reported to be 35 years, with an age at 50% maturity of 21 years (Maurer 2009). Natural mortality is estimated at 0.07-0.14, and the annual population growth rate was estimated at 1.11 (Barnett et al. 2013). When compared to the other deepwater skates examined in this paper, rate of natural mortality was similar to other deepwater Bathyraja species in the Bering Sea, and annual population growth rate was comparatively low (fifth slowest of fourteen species). Although the population growth rate estimation was uncertain, due to the number of assumptions made in the analysis, it is clear that the Commander Skate is a long-lived, slow-growing, late-maturing species that therefore has a life history that is vulnerable to fisheries exploitation and other impacts.
|Use and Trade:||This species is not known to be utilized.|
Commercial fishing is most likely the main threat to this deepwater skate. It is taken in small numbers as bycatch of commercial trawl and longline fisheries in the EBS, AI, and GOA (Olav Ormseth, unpublished data, 2015). The majority of these catches occur in longline fisheries that occur along the EBS slope and in the AI. Skates are often retained, with the rate of retention depending on skate size and market interest. In 2013 the overall retention rate for skates in the EBS was 29%, although most of these data come from the EBS shelf where the Commander Skate is not found (Ormseth 2014). Since at least the early 2000s there has been interest in directed fisheries for skates in the GOA, mainly for the Longnose Skate (Raja rhina) and Big Skate (Beringraja binoculata). Such fisheries occurred in federal waters in 2003 and 2004, and in state waters in 2009 and 2010. Although directed fishing for skates is currently prohibited, interest in these fisheries remains high.
The catch of the Commander Skate in the western Bering Sea (WBS) is unknown; however a recent assessment of the conservation status of chondrichthyans in Russian waters determined that the IUCN status of this species in Russia was “Least Concern” (Grigorov and Orlov 2013). In both Alaska and Russia, the Commander Skate occurs at depths below those where most commercial fishing occurs. In the EBS relatively little fishing effort occurs below 400 m depth, which is the upper limit to the range of this skate. If the operating depth of fisheries increases, the Commander Skate may be subject to increased fishing pressure.Other threats are unknown. Altered ocean conditions resulting from climate change are likely to affect the Commander Skate, but the impact of that threat cannot be determined at this time.
In the EBS and AI, the Commander Skate is managed as part of a skate complex comprising 13 species. Annual catch limits are determined for the complex as a whole by multiplying the estimated biomass of all skates (from surveys) by a natural mortality rate of 0.1 (Ormseth 2014a,b). Species-specific catch rates for this deepwater species are not actively tracked, but the aggregate skate catch has been below the acceptable biological catch since 2011 when the current management measures were adopted. Prior to 2011, skates were managed as part of an “Other Species” complex that included animals with widely disparate life history types including octopus, sharks, sculpins, and skates (Ormseth 2014a,b). In Russia this species does not appear to have any active management measures, but was assessed as “Least Concern” in coastal Russian Federation waters when the IUCN criteria were applied (Grigorov and Orlov 2013).
|Citation:||Ormseth, O.A., Foy, R., Davis, C.D., Ebert, D.A. & Orlov, A. 2015. Bathyraja lindbergi. The IUCN Red List of Threatened Species 2015: e.T161430A80674536.Downloaded on 16 October 2018.|
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