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Rhinobatos penggali

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES RHINOBATIDAE

Scientific Name: Rhinobatos penggali
Species Authority: Last, White & Fahmi, 2006
Synonym(s):
Rhinobatos sp. nov. [Indonesia - white spotted] subspecies
Taxonomic Notes: Prior to its description in 2006, this species was previously referred to as Rhinobatos sp. nov [Indonesia - white spotted].

This is a newly recognized species of Rhinobatos which is landed frequently in southern Bali, and also in other parts of eastern Indonesia, by gillnet fisherman. Differs markedly from the other co-occurring newly recognized species Rhinobatos jimbaranensis and also from other Rhinobatos species in this region.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2cd+3cd+4cd ver 3.1
Year Published: 2006
Date Assessed: 2006-01-31
Assessor(s): White, W.T.
Reviewer(s): Kyne, P.M., Heupel, M.R., Simpfendorfer, C.A. & Cavanagh, R.D. (Shark Red List Authority)
Justification:
Rhinobatos penggali is landed in substantial numbers by demersal gillnet fisherman targeting small rays in southern Bali and also as a minor bycatch in fisheries in southern Java and Lombok in eastern Indonesia. This species appears to be restricted to the inner continental shelf (<60 m depth) throughout eastern Indonesia from Sumatra to at least Lombok. A continuing decline in the number of mature individuals is inferred from intensive fishing pressure and a decline in the area, extent and/or quality of habitat is inferred from destructive fishing practices and pollution. Fishing practices catch a large number of juveniles as well as adults, limiting recruitment to reproductive age. Indonesia has an extremely high level of exploitation on its marine resources, and this is only likely to increase into the future in this region. Overall, since this species appears to be endemic to eastern Indonesia and occurs in a habitat that is heavily exploited by subsistence and small-scale commercial fisherman, it is categorized as Vulnerable. The large numbers of individuals of this ray that are landed and utilized for human consumption in southern Bali should be monitored into the future.

Geographic Range [top]

Range Description: Known only from Sumatra to at least Lombok in eastern Indonesia.
Countries:
Native:
Indonesia (Bali, Jawa, Sumatera)
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: Largest quantities taken in southern Bali.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Caught in water depths of typically <60 m, on relatively soft sandy substratum (White, unpubl. data).

Females attain a larger maximum size (93 cm TL) than males (84 cm TL) and males mature at about 71 cm TL compared to 74 to 76 cm TL for females. The litter size of a number of pregnant females ranged from 4 to 13 with the largest embryos 22 cm TL (W White, unpubl. data).

Age compositions, growth rates and diet not known.

Age at maturity unknown. Size at maturity 74 to 76 cm total length (TL) (females), 71 cm TL (males) (White, unpubl. data). Longevity unknown. Maximum size 93 cm TL (female), 84 cm TL (male) (White, unpubl. data). Largest in utero embryos 22 cm TL with no external yolk sac (White, unpubl. data). Average reproductive age unknown. Gestation time unknown. Reproductive periodicity unknown. Average annual fecundity or litter size: 4 to 13 embryos per litter (White, unpubl. data). Annual rate of population increase unknown. Natural mortality unknown.
Systems: Marine

Threats [top]

Major Threat(s): This species is a common component of the small-scale demersal gillnet fishery for batoids operating out of Jimbaran Bay in southern Bali and also caught in low but regular numbers off Sumatra, Java and Lombok. Approximately 60% of the catches of this species consist of immature individuals, thus a large number of rays that have not had prior opportunity to reproduce are being landed on a regular basis at the landing site of Kedonganan in Jimbaran Bay (Bali) (White, unpubl. data).

Although there are little or no trawling close inshore around Bali and Lombok, trawlers do operate in other parts of its range. The low numbers of this species observed in Java may be a result of overfishing from fishing methods such as trawling in the past, but without past baseline data on species and catch compositions of elasmobranchs in this region this cannot be confirmed.

The limited extent of occurrence of this species, particularly in the context of the fact that this region has a very high level of exploitation of marine resources (which is only likely to increase), is a major concern for this species and future monitoring is extremely important. Destructive fishing practices and pollution are also significant factors affecting marine resources in the region.

Conservation Actions [top]

Conservation Actions: None currently in place. The implementation of the National Plan of Action under the FAO International Plan of Action for the Conservation and Management of Sharks will assist in enacting measures for the conservation of this and other elasmobranchs in Indonesia.

Further research into the population structure, biology and ecology of this species is required to assess the extent to which fishing pressure, and habitat destruction is influencing this species within its range. Improved species composition data from all fisheries that take shovelnose rays and guitarfish is necessary.

Future management may involve hard decisions affecting communities adjacent to these areas.

Citation: White, W.T. 2006. Rhinobatos penggali. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 30 September 2014.
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