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Hemitrygon izuensis 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Chondrichthyes Myliobatiformes Dasyatidae

Scientific Name: Hemitrygon izuensis
Species Authority: (Nishida & Nakaya, 1988)
Common Name(s):
English Izu Stingray
Synonym(s):
Dasyatis izuensis Nishida & Nakaya, 1988
Taxonomic Source(s): Last, P.R., Naylor, G.J.P. and Manjaji-Matsumoto, B.M. 2016. A revised classification of the family Dayatidae (Chondrichthyes: Myliobatiformes) based on new morphological and molecular insights. Zootaxa 4139(3): 345-368. http://doi.org/10.11646/zootaxa.4139.3.2.
Taxonomic Notes: The genus Hemitrygon formerly was a junior synonym of Dasyatis (Kottelat, 2013); it was resurrected by Last et al. (2016) in their revision of the family Dasyatidae.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2016
Date Assessed: 2006-02-02
Assessor(s): Huveneers, C.
Reviewer(s): Kyne, P.M. & Fowler, S.L.
Justification:
This is an amended version of the 2006 assessment to accommodate the recent change in genus name from Dasyatis to Hemitrygon.

This relatively small (to 42 cm disc width) Japanese endemic stingray is known from less than ten specimens, and its biology is virtually unknown. It has only been recorded on the Izu Peninsula, Japan in depths of 10 to 20 m. It is probably taken as bycatch by the Japanese coastal bottom trawl fishery and, to a lesser extent, by set nets, but data are lacking. Research is required to better define the species' distribution, biology and catch levels. This species is Near Threatened in recognition that any fishing impact is of concern because of its extremely restricted geographical and bathymetrical distribution, while any increase in fishing pressure within its range would have dramatic effects on this regional endemic.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Found only from shallow coastal waters of the Izu Peninsula, Pacific coast of Japan (Nishida and Nakaya 1990).
Countries occurrence:
Native:
Japan
FAO Marine Fishing Areas:
Native:
Pacific – northwest
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Population size possibly small given limited range.
Current Population Trend:Unknown
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Known from less than 10 specimens. Limited depth range on the continental shelf at 10 to 20 m. Biology is virtually unknown. It is a relatively small stingray maturing at ~37 cm DW and reaching at least 42 cm DW (Nishida and Nakaya 1988).

Dasyatidae are mostly demersal in inshore waters, although several species range offshore and a few large species occur along the upper continental slopes as deep as 480 m. Several species are euryhaline while some others are confined to freshwater. All are aplacental viviparous. Litter varies between two to six young with gestation periods, which may take as long as 12 months (Last and Compagno 1999). Life history parameters taken from Nishida and Nakaya (1988).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (disc width): ~37 cm DW (male and female).
Longevity (years): Unknown.
Maximum size (disc width): 41.8 cm DW (holotype).
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.
Systems:Marine

Threats [top]

Major Threat(s): Hemitrygon izuensis can be collected by gillnets in shallow coastal waters in Japan (Nishida and Nakaya 1990). Probably taken as bycatch by the Japanese coastal bottom trawl fishery and to a lesser extent by set nets (H. Ishihara pers. comm). Care should be taken as any fishing impact on this species might have greater effects due to its narrow geographical and bathymetrical distribution. An increase of fishing pressure in this location would have dramatic effects on this endemic species.

Conservation Actions [top]

Conservation Actions: Catch levels need to be documented and careful monitoring of fishing effort in the area of occurrence is needed to ensure that the current population is not detrimentally affected. Information on the species' biology is required to inform management decisions.

Effective implementation of the Japanese National Plan of Action for the Conservation and Management of Sharks (under the FAO International Plan of Action: IPOA-Sharks) is required to facilitate the conservation and sustainable management of all chondrichthyan species in Japan.

Citation: Huveneers, C. 2016. Hemitrygon izuensis. The IUCN Red List of Threatened Species 2016: e.T60155A104118834. . Downloaded on 10 December 2016.
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