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Rhinobatos formosensis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES RHINOBATIDAE

Scientific Name: Rhinobatos formosensis
Species Authority: Norman, 1926
Common Name(s):
English Taiwan Guitarfish

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2d+3d+4d ver 3.1
Year Published: 2006
Date Assessed: 2006-01-31
Assessor(s): Compagno, L.J.V., Ishihara, H. & Marshall, A.D.
Reviewer(s): Kyne, P.M., Heupel, M.R. & Simpfendorfer, C.A. (Shark Red List Authority)
Justification:
Rhinobatos formosensis has a restricted known distribution primarily in inshore waters around Taiwan. Its occurrence in the Philippines requires confirmation. Little known of its biology, but likely to have an annual reproductive cycle like other Rhinobatos species and one observed gravid female had a litter of 14 pups. This rhinobatid is susceptible to capture in a variety of fishing gear including trawl, gillnet, line and seine net and its occurrence in inshore areas makes these rays an easy target for such fisheries. The species is impacted by direct and indirect fishing pressure and landed where the flesh is utilised. Habitat requirements are not well understood, but inshore areas are important as nursery areas for Rhinobatos species and these are being impacted upon by fishing activities and environmental degradation/pollution. The entire known area of occurrence of R. formosensis is impacted by intense and generally unregulated and unmonitored fisheries. Landed catches in Taiwan include aggregations (possibly related to pupping) of gravid females carrying near-term embryos. Rhinobatids are targeted in the Philippines and if the species occurs there also it is likely to be heavily exploited. Although exact catch data are not available, declines of greater than 30% are expected to have already occurred given the intensity of pressure on the inshore marine environment around Taiwan. Furthermore, fishing pressure continues unabated over this species' range and habitat.

Geographic Range [top]

Range Description: Restricted distribution in the Western Pacific off Taiwan and possibly a small area of the Philippines, off the mouth of Manila Bay, Luzon, although this occurrence is uncertain (Compagno and Last 1999, Compagno et al. 2005).
Countries:
Native:
Taiwan, Province of China
FAO Marine Fishing Areas:
Present - origin uncertain:
Pacific – northwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Suspected to be decreasing throughout its narrow range where it is fished both directly and indirectly.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: Inshore (from the intertidal zone to unknown depth) in warm temperate to tropical waters. Unconfirmed occurrence off northern Philippines is in 119 m depth, so also possibly an offshore species.

Little known of biology. Aplacental viviparous. Examination of a single gravid female R. formosensis at Makung fish market in the Penghu Islands, Taiwan in late May 2005 revealed a litter of 14 near-term pups ranging in size 196 to 207 mm TL (average: 201 mm TL). Sex ratio of embryos was 1:0.75 (F:M). Large follicles of ~25 mm diameter were present in the ovaries, indicating that ovulation may occur soon after parturition (P. Kyne pers. comm.). Reproductive periodicity is annual in examined Rhinobatos species.

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length cm): Unknown.
Longevity (years): Unknown.
Maximum size (total length): At least 99.7 cm TL (P. Kyne pers. comm.).
Size at birth: ~20 to 21 cm TL (P. Kyne pers. comm.).
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Probably annual (based on other Rhinobatos species).
Average annual fecundity or litter size: 14 pups/litter (based on one female) (P. Kyne pers. comm.).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Systems: Marine

Threats [top]

Major Threat(s): The restricted range, biology and inshore habitat of this species make it highly susceptible to population depletion. This rhinobatid is susceptible to capture in a variety of fishing gear including trawl, gillnet, line and seine net and its occurrence along inshore areas of the continental shelf makes these rays an easy target for such fisheries. The species is impacted by direct and indirect fishing pressure and landed where the flesh is utilised. Habitat requirements are not well understood, but inshore areas are important as nursery areas for Rhinobatos species and these are being impacted upon by fishing activities and environmental degradation/pollution.

The entire known area of occurrence of R. formosensis is impacted by intense and generally unregulated and unmonitored fisheries. In the Penghu Islands in the Taiwan Strait, the species appears to be a regular part of elasmobranch landings and observed catches of gravid females with near-term embryos, suggesting that the species is actively being fished in potential nursery areas is of concern (P. Kyne pers. comm.).

Although exact catch data are not available, declines of greater than 30% are expected to have already occurred given the intensity of pressure on the inshore marine environment around Taiwan. Furthermore, fishing pressure continues unabated over this species' range and habitat.

Conservation Actions [top]

Conservation Actions: There is a need to acquire accurate catch data from fisheries where this species is taken and landed around Taiwan. The species' occurrence in the Philippines requires validation. Better understanding of habitat requirements and critical area/habitats is required to establish best amelioration processes.

Future management will need to consider harvest and trade management with a focus on resource stewardship and livelihood alternatives.

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 management of all elasmobranch species. At the time of writing, Taiwan had not made progress towards implementing a National Plan of Action (Anon. 2004).

Bibliography [top]

Anonymous. 2004. Report on the implementation of the UN FAO International Plan of Action for Sharks (IPOA?Sharks). AC20 Inf. 5. Twentieth meeting of the CITES Animals Committee, Johannesburg (South Africa), 29 March?2 April 2004.

Compagno, L.J.V. and Last, P.R. 1999. Rhinobatidae. In: K.E. Carpenter and V.H.Niem (eds) FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophyrnidae). FAO, Rome, pp. 1423-1430.

Compagno, L.J.V., Last, P.R., Stevens, J.D. and Alava, M.N.R. 2005. Checklist of Philippine Chondrichthyes. CSIRO Marine Laboratories Report 243.

IUCN. 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 04 May 2006.

IUCN SSC Shark Specialist Group. Specialist Group website. Available at: http://www.iucnssg.org/.


Citation: Compagno, L.J.V., Ishihara, H. & Marshall, A.D. 2006. Rhinobatos formosensis. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 16 September 2014.
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