|Scientific Name:||Pteroplatytrygon violacea (Bonaparte, 1832)|
Trygon violacea Bonaparte, 1832
|Taxonomic Source(s):||Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 29 September 2016. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 29 September 2016).|
|Taxonomic Notes:||Originally described and named Trygon violacea by Bonaparte in 1832. Subsequent workers on Dasyatidae phylogenetic relationships suggested other generic affinities for Bonaparte's species. These include Dasyatis violacea and most recently Pteroplatytrygon violacea, the current valid name.|
|Red List Category & Criteria:||Least Concern (Regional assessment) ver 3.1|
|Assessor(s):||Baum, J.K., Bianchi, I., Domingo, A., Ebert, D.A., Grubbs, D., Piercy, A., Serena, F. & Snelson, F.F.|
|Reviewer(s):||Mancusi, C., Walls, R.H.L. & Allen, D.J.|
|Contributor(s):||Dulvy, N.K., Bariche, M., Buscher, E., Fordham, S. & Clò, S.|
|Facilitator/Compiler(s):||Walls, R.H.L. & Dulvy, N.K.|
Mediterranean regional assessment: Least Concern (LC)
The Pelagic Stingray is widespread, with an almost circumglobal range throughout tropical and subtropical areas of the Pacific, Atlantic, and Indian Oceans. It is perhaps the only species of stingray that occurs in pelagic oceanic waters. The species is taken as bycatch in pelagic longline fisheries around the world. It is caught frequently by tuna and swordfish longliners and mostly discarded. Post-discard survival rates are thought to be low in some areas because the fish are often discarded with serious mouth and jaw damage. Although there is some debate concerning the consistency of reporting of the Pelagic Stingray in fisheries statistics and data are lacking from several areas of the species’ range, there are no data to suggest that significant declines have occurred. Increasing fishing effort in pelagic fisheries, owing to decreasing abundance of target species (swordfish and tunas) will result in an increase in catches of this species and associated high discard mortality in some areas. Careful monitoring is therefore required. Given increasing trends observed in some regions, a wide geographic range, and the absence of evidence to suggest significant declines, the Pelagic Stingray is currently assessed as Least Concern in the Mediterranean Sea.
The Pelagic Stingray (Pteroplatytryogon violacea) is widespread, with an almost circumglobal range throughout tropical and subtropical latitudes (Mollet 2002). It also occurs throughout pelagic waters of the Mediterranean Sea (Ebert and Stehmann 2013), with a depth range of zero to 238 m.
Native:Algeria; Croatia; Egypt (Sinai); France (France (mainland)); Greece (Greece (mainland)); Israel; Italy (Italy (mainland), Sardegna, Sicilia); Libya; Morocco; Slovenia; Tunisia
|FAO Marine Fishing Areas:|
Mediterranean and Black Sea
|Population:||Nothing is known of the population size or structure of this species in the Mediterranean Sea, therefore no trends can be estimated at present.|
|Current Population Trend:||Unknown|
|Habitat and Ecology:|
This is perhaps the only species of stingray that occurs in pelagic, oceanic waters (Last and Stevens 2009). It is usually found from the surface to 100 m depth over deep, open water (Mollet 2002) but has been reported down to 238 m (Bester et al. 2007).
The Pelagic Stingray is a relatively small ray, attaining a maximum size of 80 cm disc width (DW) (Mollet et al. 2002). Females reach maturity at 39–50 cm DW (Wilson and Beckett 1970, Mollet et al. 2002, Forselledo et al. 2007, Neer 2008), and males at 37–50 cm DW (Wilson and Beckett 1970, Mollet et al.2002, Neer 2008). Females mature at three years, males mature at two years, and longevity is about 10 years (Wilson and Beckett 1970, Mollet et al. 2002, Neer 2008). The generation length is therefore 6.5 years.
This stingray is live bearing with histotrophy and has a gestation period of less than two to four months (Ranzi and Zezza 1936, Tortonese 1956, Wilson and Beckett 1970, Forselledo et al. 2007). Copulation takes place in spring and females move inshore during summer to give birth (Tortonese 1956, Whitehead et al. 1984, Forselledo et al. 2007). Females give birth to four to 13 pups per litter (average six) (Tortonese 1956, Fisher et al. 1987, Ebert 2003, Neer 2008) and newborns measure between a mean range of 14.3 and 24.1 cm DW (Mollet 2002, Mollet et al. 2002). In the Mediterranean Sea females give birth in the Bay of Naples before migrating to warmer water (Lo Bianco 1909, Ranzi 1933, Mollet 2002). Individuals in the Bay of Naples appeared to migrate as the water became colder.
|Generation Length (years):||6.5|
|Movement patterns:||Full Migrant|
|Use and Trade:||The Pelagic Stingray is not used or traded commercially in the Mediterranean region.|
The major threats to the Pelagic Stingray are pelagic longline fisheries for tunas, billfishes, and other pelagic shark species (Neer 2008). It is caught frequently by tuna and swordfish longliners and mostly discarded (Vaske 2000, Mollet 2002, Domingo et al. 2005, Forselledo et al. 2007). The magnitude of regional and indeed global catch is currently unknown.
There is evidence for skewed sex ratios in this species; whether these ratios are obtained in actual fisheries bycatch is unknown, however if so, an asymmetric take of this ray could potentially affect the long term population stability of the Pelagic Stingray (Neer 2008).
In the Mediterranean Sea, this stingray is captured incidentally by pelagic longline fisheries and is mostly discarded, with a low discard survival rate due to damage to jaws and/or mouth as a result of treatment on board fishing vessels. The magnitude of Mediterranean-wide catches is unknown. Reports of the Common Stingray (Dasyatis pastinaca) in pelagic fisheries catches in the Mediterranean Sea may refer to the Pelagic Stingray. In Italian seas, the Pelagic Stingray is the most commonly caught elasmobranch species in the Albacore longline fisheries and the second most common elasmobranch in swordfish longline fisheries catch (Filanti et al. 1986, Di Natale et al. 1995, Orsi Relini et al. 1999, Relini et al. 2010). Total bycatch of this stingray in the swordfish fishery in the Ligurian Sea was estimated at ~2,000 individuals (up to 20 per boat) in 1995, although the catch was smaller and more variable in 1996 (Mollet 2002). Rey and Alot (1984) reported the results of a swordfish longline survey in Mediterranean Spanish waters, recording only two individuals in 11 fishing operations (<0.001). The Pelagic Stingray is also occasionally taken by recreational fisheries (Fischer et al. 1987), which presumably does not have a significant effect on the population.
No species-specific measures are in place in the Mediterranean Sea. Further efforts should be made to gather data from longline fishing vessels and other commercial fishing operations that may encounter this species. Continued research efforts aimed at careful monitoring of the population are required.
A recent study suggested that the use of large circle hooks by commercial and artisanal swordfish longline fisheries has the potential to reduce the negative effect that fishing has on this stingray (Kerstetter and Graves 2006, Piovano et al. 2009).
|Citation:||Baum, J.K., Bianchi, I., Domingo, A., Ebert, D.A., Grubbs, D., Piercy, A., Serena, F. & Snelson, F.F. 2016. Pteroplatytrygon violacea. The IUCN Red List of Threatened Species 2016: e.T161731A16527897.Downloaded on 18 August 2018.|
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