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Notoraja sticta

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES ARHYNCHOBATIDAE

Scientific Name: Notoraja sticta
Species Authority: McEachran & Last, 2008
Common Name(s):
English Blotched Skate
Taxonomic Notes: Four Notoraja species were previously identified by Last and Stevens (1994) but remained undescribed until recently (McEachran and Last 2008, Last and Stevens 2009).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2010-11-25
Assessor(s): Beckmann, C. & Huveneers, C.
Reviewer(s): Ebert, D.A. & Kyne, P.M.
Justification:

The Blotched Skate (Notoraja sticta) has only been found on the Great Australian Bight continental slope off South Australia. Its depth range is approximately 820–1,200 m, however the benthic habitats of Australasia below 1,400 m have not been adequately sampled and new depth records will doubtless emerge when the deepwater ichthyofauna is surveyed. Commercial fisheries have operated within this species’ range, however, waters deeper than 750 m have been closed since 2007 to protect Orange Roughy (Hoplostethus atlanticus). Prior to the closure, the deepwater was heavily fished for Orange Roughy and the levels of bycatch during this period were largely unreported. While there are some questions as to the level of affect this fishery had on bycatch species such as the Blotched Skate, fisheries targeting Orange Roughy generally fish on seamounts and have a low level of bycatch when compared to other fisheries. As a result, the species is assessed as Least Concern. However, further research is required on the species’ biology, occurrence, population trends, and capture in fisheries. Given the general vulnerability of large skates to overfishing and that the species would be likely to be impacted if deepwater trawling were to reopen, bycatch levels need to be monitored.

Geographic Range [top]

Range Description: The Blotched Skate (Notoraja sticta) is known only from the mid-continental slope of the Great Australian Bight, South Australia (33°30′ S, 130°24′ E to 35°10′ S, 133°46′ E) (McEachran and Last 2008, Last and Stevens 2009).
Countries:
Native:
Australia (South Australia)
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population:

The Blotched Skate is known from a handful of specimens but probably occurs more widely across southern Australia. There are no details available on population size, structure, or trends.

Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The Blotched Skate occurs on continental slope areas in a depth range of approximately 820–1,200 m. However, the benthic habitats of Australasia below 1,400 m depth have not been adequately sampled and new depth records will doubtless emerge when the deepwater ichthyofauna is surveyed (Last and Yearsley 2002). The Blotched Skate attains at least 63 cm total length (TL), with males maturing at about 52 cm TL (McEachran and Last 2008).
Systems: Marine

Use and Trade [top]

Use and Trade:

The Blotched Skate is not known to be traded and when caught as bycatch it was generally discarded at sea.

Threats [top]

Major Threat(s):

The Blotched Skate was previously taken as bycatch within the Great Australian Bight Trawl Sector (GABTS), one of the four sectors of the Commonwealth managed Southern and Eastern Scalefish and Shark Fishery (SESSF). The GABTS covers an extensive area of southern Australian waters, from Cape Leeuwin in Western Australia to Cape Jervis in South Australia, and out to the edge of the Australian Fishing Zone (AFZ). It includes a continental shelf fishery, operating in depths of 200 m or less and an upper slope fishery operating at depths of 200–1,000 m. However, in most shelf waters, the trawlers operate at 120–160 m depth, mainly targeting Bight Redfish (Centroberyx gerrardi) and Deepwater Flathead (Neoplatycephalus conatus).

Previously, there was a seasonal deepwater slope fishery operating at depths greater than 750 m targeting Orange Roughy (Hoplostethus atlanticus) (Knuckey and Brown 2002). However, this fishery was closed in 2007 due to the unsustainability of Orange Roughy stocks. Bycatch in the Orange Roughy fishery has been reported as less than in many other trawl fisheries since aggregations around seamounts are primarily targeted (Lack et al. 2003). This is indicated by the results of a bycatch survey in the deepwater trawl fishery in the Great Australian Bight Far West Zone with up to 99.6% being the target species of Orange Roughy (Knuckey and Brown 2002).

The continental shelf fishery appears to have no interaction with this species as a majority of trawling takes place between 120–160 m depth, not overlapping with the depth range of the Blotched Skate which is 820–1,200 m. The previously existing Orange Roughy fishery, which targeted depths greater than 750 m may have had interactions with the Blotched Skate, however as indicated there were low levels of bycatch reported in this fishery.

Conservation Actions [top]

Conservation Actions:

No conservation actions are currently in place for the Blotched Skate. Given that its depth range is 820–1,200 m, with the closure of waters >750 m, there is no need for further mitigation measures at this time.


Citation: Beckmann, C. & Huveneers, C. 2011. Notoraja sticta. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 22 October 2014.
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