|Scientific Name:||Urolophus orarius Last & Gomon, 1987|
|Taxonomic Notes:||Valid sister species of U. cruciatus.|
|Red List Category & Criteria:||Endangered B1ab(v) ver 3.1|
|Assessor(s):||Last, P.R., Kyne, P.M. & Marshall, L.J.|
|Reviewer(s):||Baker, J., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)|
Urolophus orarius is a small South Australian endemic stingaree restricted to a narrow range in the eastern Great Australian Bight between Ceduna and Beachport. Furthermore, it occupies a narrow habitat band on the inner continental shelf at depths restricted to 20 to 50 m. Given its endemism, this species is a key indicator of the Gulfs Province of southern Australia. It is considered to be sparse and the population size is likely to be small based on low abundance and narrow range. The Southern and Eastern Scalefish and Shark Fishery operates in the eastern portion of the species' range and South Australian Prawn Trawl Fisheries operate over much of the remainder, particularly in the Spencer Gulf and the Gulf St. Vincent. It has a high encounterability and selectivity to trawl fishing making it extremely vulnerable due to the fact that it is being fished at low to moderate levels. It would not tolerate high levels of fishing if this became a reality. Urolophids generally have a low fecundity (1 to 2 young/year) and gravid females are renowned for aborting embryos upon capture and handling. Further information is required on population size, habitat requirements, biology and bycatch. Based on its restricted distribution, small population size, life history and continued trawling activities (inferring a continuing decline in the number of mature individuals) over its narrow depth band, this species is assessed as Endangered.
|Range Description:||Known only from the eastern Great Australian Bight, between Ceduna and Beachport (South Australia) (Last and Stevens 1994). Narrow ranging endemic and key indicator of the Gulfs Province of southern Australia. Not known in waters less than 20 m deep, however, further surveys of South Australian waters <20m deep is required. Extent of occurrence estimated to be <5,000 km².|
Native:Australia (South Australia)
|FAO Marine Fishing Areas:|
Indian Ocean – eastern
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Abundance is "sparse" (Walker 2004). Population size is likely to be small based on low abundance within the narrow range.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||Inner continental shelf in depths of 20 to 50 m (narrow habitat band) (Last and Stevens 1994). Presumably on soft substrates. Likely to have low fecundity (1 to 2 young/year) as with other urolophid species (for example, see White et al. 2001).
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length cm): Unknown (female; 23 cm TL (Last and Stevens 1994) (male).
Longevity (years): Unknown.
Maximum size (total length): 31 cm TL (Last and Stevens 1994).
Size at birth (cm): Unknown.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: Unknown.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Within the Southern and Eastern Scalefish and Shark Fishery (SESSF), Urolophus oroarius is considered to have a low catch susceptibility to all gear types (Walker 2004). Catch susceptibility is defined as "availability" x "encounterability" x "selectivity" x "post-capture mortality" (Walker 2004). When these parameters are considered separately it is shown that "availability" results in the assignment of a low catch susceptibility for otter trawl gear. The species is restricted to SA waters and given this range is thus not available to the majority of the fishery as activities are centred further to the east. Urolophus orarius has a high encounterability, a high selectivity and a medium post-capture mortality to otter trawl gear.
The South Australian Prawn Fisheries operate over the remainder of the range of U. orarius. There are presently 10 licences for the Gulf St. Vincent Prawn Fishery, 39 in the Spencer Gulf Prawn Fishery and three in the West Coast Prawn Fishery (PIRSA 2004). Data on bycatch of this species in SA Prawn Fisheries is not available, but given the species area of occurrence it is certainly interacting with this fishery. Carrick (1997) did not report U. orarius as bycatch in the Spencer Gulf Prawn Fishery in 219 trawls (mostly of 30 minutes duration) possibly indicating the apparent rarity of the species. Historically, fishing pressure has been intense in parts of this fishery, particularly in the Spencer Gulf.
The species' reliance on invertebrate-rich benthic habitats is unknown, and so there is a potential risk of habitat alteration through trawling activities. Prawn trawling in Gulf St. Vincent has been shown to have a considerable impact on epifaunal assemblages (Tanner 2003), although changes in infauna consistent with the effects of trawling were not detected (Drabsch et al. 2001). These authors concluded that prawn trawling in South Australia does not have consistent effects on infaunal assemblages given the high amount of spatial and temporal variability they observed (Drabsch et al. 2001).
Gravid female urolophids are renowned for aborting embryos upon capture and handling, so even it bycatch is returned alive to the water, reproductive output can be lost.
Better iteration of population size, habitat requirements and distribution. Monitoring of habitat change and bycatch in all trawl fisheries within the species range.
South Australian prawn trawl fisheries are managed by traditional measures such as limited entry, vessel and gear restrictions as well as seasonal closures and rotation of trawling grounds. Other measures have also been implemented in order to reduce effects on non-target species such as gear modifications and improvements aimed at bycatch reduction and reduced sorting times. These measures need to be monitored to assess their effectiveness (Baker in prep).
An assessment of the conservation status of Urolophus orarius is underway for the South Australian Government (Baker in prep).
The effective implementation of the Australian National Plan of Action for the Conservation and Management of Sharks (Shark Advisory Group and Lack 2004) (under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA-Sharks) will help to facilitate the conservation and sustainable management of all chondrichthyan species in Australia.
|Citation:||Last, P.R., Kyne, P.M. & Marshall, L.J. 2006. Urolophus orarius. The IUCN Red List of Threatened Species 2006: e.T60100A12299964.Downloaded on 24 March 2018.|
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