Tetronarce tokionis 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Rajiformes Torpedinidae

Scientific Name: Tetronarce tokionis
Species Authority: (Tanaka, 1908)
Common Name(s):
English Longtail Torpedo Ray
Tetronarcine tokionis Tanaka, 1908
Torpedo tokionis (Tanaka, 1908)
Taxonomic Source(s): Eschmeyer, W.N. (ed.). 2015. Catalog of Fishes. Updated 3 August 2015. Available at: (Accessed: 3 August 2015).
Taxonomic Notes: The species has been confused with another recently described Torpedo ray from Taiwan, T. formosa.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2009
Date Assessed: 2007-06-25
Assessor(s): Haas, D.L., Ebert, D.A., Nakaya, K., Tanaka, S. & Orlov, A.
Reviewer(s): Valenti, S.V. & Musick, J.A. (Shark Red List Authority)
Torpedo tokionis is a poorly known, uncommon electric ray, distributed in the Pacific waters of Japan from Hokkaido to Ryukyu Islands and Taiwan. It has been recorded in trawl surveys at depths of 220-1,100 m. It is a demersal species found over stone, sand or mud habitats. Very little is known about the population, biology or ecology of this species. It is occasionally seen in fish markets. The species is likely an occasional bycatch of trawl and gillnet fisheries and may be utilized for fishmeal, however it is usually discarded. The species may have some refuge from fishing pressure at the deeper extent of its depth range. No information is available on population trends, bycatch levels or the affect of fisheries on this species and it is currently assessed as Data Deficient.

Geographic Range [top]

Range Description: Northwest Pacific: from the Pacific coast of Tohoku District, Japan, southward to the East China Sea, Ryukyu Islands, and Taiwan (Huang 2001, Nakabo 2002, D.A. Ebert unpubl. data).
Countries occurrence:
Japan; Taiwan, Province of China
FAO Marine Fishing Areas:
Pacific – northwest
Lower depth limit (metres): 1100
Upper depth limit (metres): 220
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Very little is know about the population of this species, but it seems to be uncommon. Very few specimens were caught in an experimental otter trawl fisheries investigation, which was conducted in the 1980s and 1990s. The species was captured in trawls from 220 m deep in Okinawa Trough, East China Sea and 1,100 m deep from the Tohoku slope off northern Japan (Nakaya et al. 1992).
Current Population Trend: Unknown
Additional data:
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: A little-known demersal species found in stone, sand or mud habitats at depths of 220-1,100 m (Nakaya and Shirai 1992, Nakaya et al. 1992). Members of the Torpedinidae family exhibit aplacental viviparity. Males mature by 67.5 cm total length (TL) and females are larger (Haas and Ebert 2006). Maximum size is 113.6 cm TL and size at birth is ~20.0 cm TL (Hass and Ebert 2006).
Systems: Marine

Threats [top]

Major Threat(s): This species is occasionally caught as bycatch in bottom trawl and gillnet fisheries off Japan and Taiwan. This species has been observed in fish markets in Tokyo, Japan, and Tachi, Taiwan. In Taiwan, it is only known from these fish markets where it is occasionally seen (usually one or two a day) (D. Ebert pers comm. 2007). The electric discharge emitted by this species makes it unpleasant to handle and the meat is of poor quality. It is often discarded or utilized for fishmeal (D. Ebert pers. obs. 2007).

Conservation Actions [top]

Conservation Actions: There are no conservation measures in place for this species. Assessment and monitoring of catches and population trends is required, as well as research on the species' life-history characteristics.

Citation: Haas, D.L., Ebert, D.A., Nakaya, K., Tanaka, S. & Orlov, A. 2009. Tetronarce tokionis. The IUCN Red List of Threatened Species 2009: e.T161676A5478248. . Downloaded on 25 November 2015.
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