|Scientific Name:||Dipturus acrobelus Last, White & Pogonoski, 2008|
The Deepwater Skate (Dipturus acrobelus) was previously misidentified as Bight Skate Raja gudgeri (Last et al. 1983).
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Robbins, R. & Huveneers, C.|
|Reviewer(s):||Walls, R.H.L. & Kyne, P.M.|
|Contributor(s):||Walls, R.H.L. & Kyne, P.M.|
|Facilitator/Compiler(s):||Kyne, P.M. & Walls, R.H.L.|
The Deepwater Skate (Dipturus acrobelus) is a little-known, large skate species reported from southern Australian waters at depths of 450–1,330 m, although mainly at 800–1,000 m. It is found on the continental slope off southern Australia from east of Crowdy Head, New South Wales to the Great Australian Bight, Western Australia, including Tasmania. The species may be sensitive to population declines from fishing pressure due to its large size. There are few specific details available regarding its ecology or life history. The Southern and Eastern Scalefish and Shark Fishery (including the East Coast Deepwater Trawl, Great Australian Bight and Commonwealth Trawl Sectors) operates within this species’ range off southern and eastern Australia, in which it is taken as bycatch. However, it has a relatively wide range and the estimated annual catch levels are relatively low. Importantly, since this species is most commonly found in waters of 800–1,000 m and deepwater trawling is currently prohibited deeper than 700 m over much of its range, the effect of these fisheries is likely to be small. As such, this skate is assessed as Least Concern. However, research is required to accurately define its range, as well as population size, structure and trends. Given its occurrence in areas where deepwater trawl fisheries operate, and the general sensitivity of large skates to overfishing, bycatch levels need to be monitored.
|Previously published Red List assessments:|
|Range Description:||The Deepwater Skate is endemic to Australia and is found on the continental slope off southern Australia from east of Crowdy Head, New South Wales to the Great Australian Bight, Western Australia, including Tasmania (Last and Stevens 2009). However, the full extent of its range, particularly to the west, is uncertain and this range is likely to expand through additional thorough surveys of the continental slope off southwest Australia (Last and Stevens 2009).|
Native:Australia (New South Wales, South Australia, Tasmania, Victoria, Western Australia)
|FAO Marine Fishing Areas:|
Indian Ocean – eastern; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Deepwater Skate is apparently common throughout its range (Last and Stevens 2009), however details of population size, structure, or trends are currently unavailable.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:|
This demersal species occurs at depths of 446–1,328 m although mainly in 800–1,000 m (Last et al. 2008, Last and Stevens 2009). There are no species-specific details available on habitat. A large skate, it attains at least 137 cm total length (TL); adolescent males range from 77.6–85.5 cm TL; males reach maturity at 89–95 cm TL; smallest juvenile 20.2 cm TL (Last et al. 2008). There are no other details available regarding its ecology or life history.
|Use and Trade:||While most skates caught off southeast Australia used to be discarded, there is now an increasing trend for the larger (adult) individuals to be retained for the local market. Of an estimated annual catch of 16 tonnes of Deepwater Skate in the Southern and Eastern Scalefish and Shark Fishery (SESSF) between 2000 and 2006, 19% were retained for market (Walker and Gasson 2007).|
This species might be taken as bycatch within three of the four sectors of the Commonwealth managed Southern and Eastern Scalefish and Shark Fishery (SESSF) (that is, the East Coast Deepwater Trawl, Great Australian Bight Trawl (GABTS), and Commonwealth Trawl sectors). The current known range of this species overlaps with these fisheries. The mean annual catch rate of this skate in the SESSF between 2000 and 2006 of 16 tonnes included 13 tonnes from the 200–599 depth range (Walker and Gason 2007).
The GABTS upper continental slope sub-fishery operates in waters 200–700 m depth, so only in the shallower regions of this species’ known range. The GABTS deepwater slope sub-fishery operated in waters from 700–1,000 m before waters deeper than 700 m were closed in 2007 to protect stocks of Orange Roughy (Hoplostethus atlanticus) in both the GABTS and the Commonwealth Trawl Sector (Moore and Curtotti 2014, Penney et al. 2014). Since this skate is most commonly found in waters 800–1,000 m, the effect of these fisheries is likely to be small. Overall fishing effort in the Commonwealth Trawl Sector is still intensive but in decline (Penney et al. 2014), while that in the GABTS has also declined, with the majority of the remaining effort focused at depths shallower than this species' main depth range (Moore and Curtotti 2014). However, considering the bycatch level within the 200–599 m depth range (Walker and Gason 2007) and that the species mainly occurs at deeper depths, the deepwater trawl fisheries are likely to be of concern should the deepwater be reopened in the future. Fishing effort in the East Coast Deepwater Trawl sector over recent years has been extremely low (Penney and Curtotti 2014) and is therefore of little concern, but should be monitored for any increases in the future.
No species-specific conservation actions are currently in place. Given the sensitivity of large skates to overfishing, bycatch levels need to be continually monitored. Areas below 700 m closed to trawling off southeast Australia would provide refuge for this species (Penney et al. 2014).
|Citation:||Robbins, R. & Huveneers, C. 2015. Dipturus acrobelus. The IUCN Red List of Threatened Species 2015: e.T195444A68620069.Downloaded on 20 November 2017.|
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