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Gymnura zonura

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES GYMNURIDAE

Scientific Name: Gymnura zonura
Species Authority: (Bleeker, 1852)
Common Name(s):
English Zonetail Butterfly Ray
Synonym(s):
Aetoplatea zonura Bleeker, 1852
Taxonomic Notes: Previous studies of the family Gymnuridae have divided it into two genera based on the presence or absence of a dorsal fin; Aetoplatea with a dorsal fin and Gymnura without (Murdy et al. 1997, Compagno and Last 1999, Vossoughi and Vosoughi 1999, Oshigou et al. 2004, Yano et al. 2005). A recent taxonomic review of the Australian Butterfly Ray Gymnura australis (Ramsay and Ogilby 1886), supports the amalgamation of all species into a single genus; Gymnura (Jacobsen 2007). Jacobsen (2007) found that dorsal fin development in G. australis is variable and inconsistent with the two genus hypothesis, thus suggesting that Aeteoplata should be designated as a junior synonym.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2d+3d+4d ver 3.1
Year Published: 2006
Date Assessed: 2006-01-31
Assessor(s): White, W.T.
Reviewer(s): Kyne, P.M., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)
Justification:
Aetoplatea zonura is a large (to 95 cm disc width) inshore butterfly ray which is landed in substantial numbers by demersal fisheries operating throughout its range and is taken in very large numbers by gillnet fisherman targeting small rays in southern Bali in eastern Indonesia. This species has a disjunct distribution off India, Indonesia, Singapore and Thailand and is restricted to the inner continental and coastal shelves with a narrow depth range (<40 m), which is heavily exploited throughout much of the species' range and in most areas they are all retained and utilized for human consumption. Fecundity appears to be low with one pregnant female containing only four embryos. The criteria met by this species for the category of Vulnerable are A2d+3d+4d due to the high level of exploitation of coastal shelf regions within its known range which is only likely to increase into the future. It is inferred that declines of 30% or more have already occurred, although species-specific data are not available. The species is highly susceptible to a variety of gear types and its apparent restricted life history would limit its ability to recover from population depletion. Careful monitoring of catches of this species throughout its range need to be carried out into the future due to this high level of exploitation that occurs in its known range.

Geographic Range [top]

Range Description: Disjunct distribution in the Eastern Indian and Western Central Pacific: off the coasts of India, Indonesia, Singapore and Thailand (Compagno and Last 1999).
Countries:
Native:
India; Indonesia; Singapore; Thailand
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Caught in relatively high numbers in the demersal gillnet fisheries in Indonesia, particularly off central Java and southern Bali. Reported as locally common (Compagno and Last 1999).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: An inshore gymnurid occurring to depths of about 40 m over soft substrates. A. zonura is aplacental viviparous, attaining a maximum size of 95 cm DW and males mature at about 48 cm DW (W. White unpubl. data). One pregnant female possessed four embryos, size at birth not known.

Age and growth and diets have not been determined for this species. Gut samples from several specimens caught off Bali in Indonesia had mostly benthic crustaceans and unidentified teleosts in their guts (W. White unpubl. data).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (disc width): Unknown (female); 48 cm DW (W. White unpubl. data) (male).
Longevity (years): Unknown.
Maximum size (total length/disc width): 65 cm TL, 85 cm DW (Last and Compagno 1999), 95 cm DW (W. White. unpubl. data).
Size at birth (cm): Unknown.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: 4 in one pregnant female (W. White unpubl. data).
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Systems: Marine

Threats [top]

Major Threat(s): This species is susceptible to a variety of gear types and is commonly caught by demersal gillnet, trawl and trammel net fisheries throughout its range.

In Indonesia, large numbers of juveniles are caught in the demersal gillnet, trawl and trammel net fisheries, particularly around Java. Larger specimens are also caught in the tangle net fisheries that target rhynchobatids in the region. In southern Bali, small batoids are targeted by inshore gillnets and this species forms a substantial component to the catch of this fishery (W. White, unpubl. data). All caught are retained. Intensive demersal fisheries occur in India, in the species' known distribution (Hanfee 1999) and fishing is intense in the coastal waters of Thailand. There is a very high level of exploitation on the habitat that this species occurs in throughout its entire range.

Conservation Actions [top]

Conservation Actions: None in place. Careful monitoring of catches of this species throughout its range need to be carried out into the future due to this high level of exploitation that occurs in its known range.

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 sustainable management of all chondrichthyan species in the region. See Anon. (2004) for an update of progress made by nations in the range of A. zonura.

Citation: White, W.T. 2006. Gymnura zonura. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 02 August 2014.
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