|Scientific Name:||Plesiobatis daviesi|
|Species Authority:||(Wallace, 1967)|
|Taxonomic Notes:||This species is distinct in shape from all other stingarees, resulting in its placement in the separate monospecific family, Plesiobatidae. There has never been a comparison of populations of this species, which needs to be undertaken to elucidate whether there is in fact more than one species.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||White, W.T., Kyne, P.M. & Holtzhausen, H.|
|Reviewer/s:||Fowler, S.L., Compagno, L.J.V. & Cavanagh, R.D.|
Plesiobatis daviesi is demersal on the continental slope in depths of 275?680 m (and occasionally in shelf waters) with a sporadic and patchy distribution in the Indo-Pacific (Southern Africa, India, Indonesia, Australia, South China Sea, Japan and Hawaii). Biology is poorly known and research needs to elucidate the relationship between different populations. The giant stingaree is occasionally caught in local deepwater trawl and longline fisheries, is only landed in low numbers and deepwater fishing is usually relatively restricted within most of its range. In Indonesia, only a small deepwater longline fishery operates between 300 and 600 m and the species is thus not taken in any great quantities compared to other elasmobranch species (W. White, pers. obs). Similarly the deepwater fishery in Taiwan only catches low numbers of this species (D. Ebert pers. comm). In Australian waters, there is minimal fishing pressure on the species? range off Western Australia and Queensland. This species is assessed as Least Concern due to the limited number of slope fisheries presently throughout much of its range. However, the large size of this species and low number of records indicate low productivity, hence poor resilience to fisheries, and possible rarity; further expansion of deepwater fisheries within its range in the future could pose a potential threat, at which time its conservation status would need reassessing.
|Range Description:||Sporadic distribution in the Indo-Pacific. The species has mainly been collected from tropical Australia (Last and Stevens 1994).|
Native:Australia (New South Wales, Queensland, Western Australia); China; India; Indonesia; Japan; Mozambique; South Africa (KwaZulu-Natal); United States (Hawaiian Is.)
|FAO Marine Fishing Areas:||
Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – southwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||It is reported to be locally common (Compagno and Last 1999), which may be the case off tropical Australia, however the generally low numbers of records elsewhere may indicate rarity.|
|Habitat and Ecology:||
The largest and most widespread stingaree which lives in deeper water than any of its relatives in the family Urolophidae (Last and Stevens 1994). An upper continental slope species on soft substrates, generally at depths of 275 to 680 m (350 to 680 m in Australia), however there is a single record from 44 m on the continental shelf off Mozambique (Last and Stevens 1994, Compagno and Last 1999).
Like most other deepwater batoids, the biology of Plesiobatis daviesi is poorly known. Probably viviparous but details of reproduction unknown. Its large size and deepwater occurrence suggests a probable small litter size and long gestation period, resulting in a slow biology (L.J.V. Compagno pers. comm.). Ebert et al. (2002) report a juvenile female at 189 cm TL and an adolescent female at 201 cm TL. Smallest examined mature male was 130 cm TL (Last and Stevens 1994). Maximum size at least 200 cm TL in Australia and elsewhere reported to 270 cm TL (Last and Stevens 1994). Consistent with geographic variability in maximum size, size at maturity probably also varies regionally. Size at birth is unknown, however Compagno and Last (1999) report that a 50 cm TL freeliving individual had an umbilical scar.
Diet consists of fishes (including mesopelagic species suggesting that this species may migrate into the water column to feed), crustaceans (crabs, penaeid prawns, lobsters) and cephalopods (Compagno and Last 1999, Ebert et al. 2002).
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length/disc width): 201 cm TL (116 cm DW) or more (Southern Africa; Ebert et al. 2002) (female); 130 cm TL or less (Australia; Last and Stevens 1994) (male).
Longevity (years): Unknown.
Maximum size (total length): At least 200 cm TL (Australia); 270 cm TL elsewhere (Last and Stevens 1994).
Size at birth: Less than 50 cm TL (Compagno and Last 1999).
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.
Available specific data are lacking, the species is known to be taken in deepwater benthic trawls and on deepset longlines. Not targeted and not known to be taken in any considerable numbers in any one region within its range, although it can be taken regularly by longliners off KwaZulu-Natal (L.J.V. Compagno pers. comm.). In Indonesia, only a small deepwater longline fishery operates between 300?600 m and the species is thus not taken in any great quantities compared to other elasmobranch species (W. White, pers. obs). Similarly the deepwater fishery in Taiwan only catches low numbers of this species (D Ebert pers. comm.).
In Australian waters, there is minimal fishing pressure on the species? range off Western Australia and Queensland. The Commonwealth managed Western Trawl Fisheries (continental slope off Western Australia) is comprised of two small-scale demersal trawl fisheries managed by limited entry with a total of 18 permits (over a wide geographical area) (AFMA 2003a). The Commonwealth managed Coral Sea Fishery (off the Queensland continental shelf) is a small-scale fishery with a demersal line sector (nine permits) and a trawl sector (two permits). The fishery is managed by limited entry and catch and effort by these sectors is very low (most operators fish a maximum of 20 days per year) (AFMA 2003b).
Further information is required from catches of this species in order to better define its distribution and obtain life history data. Bycatch in globally expanding deepwater fisheries needs to be documented and monitored.
The development and implementation of management plans (national and/or regional e.g., under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA?Sharks) are required to facilitate the conservation and sustainable management of all chondrichthyan species in the region. See Anon. (2004) for an update of progress made by nations in the range of P. daviesi.
|Citation:||White, W.T., Kyne, P.M. & Holtzhausen, H. 2006. Plesiobatis daviesi. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 07 March 2014.|
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