Hexatrygon bickelli 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Hexatrygonidae

Scientific Name: Hexatrygon bickelli
Species Authority: Heemstra & Smith, 1980
Common Name(s):
English Sixgill Stingray
Taxonomic Notes: Several species of sixgill stingrays have been named from the Western Pacific; H. longirostris, H. yangi, H. taiwanensis and H. brievirostra, mainly on snout length and shape. However, these forms may be based on variation with growth and state of preservation. The current opinion of the occurrence of a single species of sixgill stingray, H. bickelli based on morphological comparisons, should be confirmed by genetic analyses.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2015
Date Assessed: 2015-05-05
Assessor(s): McCormack, C., Wang, Y., Ishihara, H., Fahmi, Manjaji Matsumoto, B.M., Capuli, E. & Orlov, A.
Reviewer(s): Kyne, P.M. & Walls, R.H.L.
Contributor(s): Kyne, P.M.
Facilitator/Compiler(s): Kyne, P.M. & Walls, R.H.L.
The Sixgill Stingray (Hexatrygon bickelli) is a large (to 168 cm total length) deepwater stingray, known from depths of 30-1,120 m. It has a wide but patchy distribution on continental slopes and seamounts in the Northwest and Central Pacific Ocean, off Australia and India in the Eastern Indian Ocean and off South Africa in the Western Indian Ocean. While several species of sixgill stingray (Hexatrygon species) have been described, a single species - the Sixgill Stingray - is recognized. The species is taken as bycatch in deepwater trawl fisheries, although no information is available on the numbers caught. It is of concern that there has been a decline in the numbers landed in Taiwan, but no quantitative data are currently available. In other areas of this species' geographic range, such as Hawaii and Indonesia, deepwater trawl fisheries are absent or restricted and globally it is currently listed as Least Concern. Catches and population trends should be monitored and the species' status in the Northwest Pacific should be investigated.
Previously published Red List assessments:
2009 Least Concern (LC)

Geographic Range [top]

Range Description: The Sixgill Stingray is known from Southwest India, the South China Sea off China, Taiwan, Indonesia, the Philippines, Australia (Western Australia off Exmouth Plateau to Shark Bay; Queensland off Flinders Reef), New Caledonia, Hawaii, and eastern South Africa (Eastern Cape off Port Elizabeth and Port Alfred, possibly Western Cape near Cape Agulhas) (Compagno 1999, Last and Stevens 2009, Babu et al. 2011).
Countries occurrence:
Australia (Queensland, Western Australia); China; India; Indonesia (Jawa); Japan; New Caledonia; Philippines; South Africa (Eastern Cape Province); Taiwan, Province of China (Taiwan, Province of China (main island)); United States (Hawaiian Is.)
FAO Marine Fishing Areas:
Atlantic – southeast; Indian Ocean – eastern; Indian Ocean – western; Pacific – eastern central; Pacific – western central; Pacific – northwest
Lower depth limit (metres): 1120
Upper depth limit (metres): 30
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: A rare species with a patchy, widespread distribution. Nothing is known of the population size or structure.
Current Population Trend: Unknown
Additional data:
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: The Sixgill Stingray is a deepwater, benthic ray, mostly found on the continental slope at depths of 362-1,120 m, although there have been two records of the species stranding on beaches off South Africa and one additional live specimen photographed feeding at about 30 m depth off Japan by divers (Compagno 1999, H. Ishihara, pers. obs.). It is found on sandy mud to rocky bottom substrates (B. Séret, pers. comm.).

This species is viviparous and females have been observed with up to three term foetuses (Compagno 1999). The Sixgill Stingray reaches a maximum total length (TL) of at least 168 cm (adult female). Males are estimated to mature at 110 cm TL and females are estimated to mature at 113 cm TL (Compagno 1999, B. Séret, pers. comm.). Size at birth is about 48 cm TL (Compagno 1999).
Systems: Marine

Use and Trade [top]

Use and Trade: Nothing is known of the use or trade of this batoid.

Threats [top]

Major Threat(s): The Sixgill Stingray is infrequently captured in bottom trawl fisheries (Compagno 1999), however there are no quantitative data on the numbers caught or landed throughout its range. In Taiwan, this species forms part of the bycatch in both coastal and offshore bottom trawl fisheries (H. Ishihara, pers. obs.). It is of concern that this stingray appears in the landed bycatch of deep bottom trawl fisheries much less than it did in previous years (B. Séret, pers. comm.). The Sixgill Stingray is a large and presumably slow growing species, with a relatively large size at maturity, deeming it particularly susceptible to overfishing. In other parts of its geographic range, this species' bathymetric distribution may extend below the range of fisheries.

Conservation Actions [top]

Conservation Actions: There are currently no species-specific conservation measures in place. Close monitoring of catches in deep bottom trawl fisheries in the Sixgill Stingray's range is required in order to assess the threats to this species.

Citation: McCormack, C., Wang, Y., Ishihara, H., Fahmi, Manjaji Matsumoto, B.M., Capuli, E. & Orlov, A. 2015. Hexatrygon bickelli. The IUCN Red List of Threatened Species 2015: e.T161674A68626659. . Downloaded on 27 November 2015.
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