|Scientific Name:||Rhinoptera javanica|
|Species Authority:||Müller & Henle, 1841|
|Taxonomic Notes:||The genus Rhinoptera is a taxonomically perplexing group that requires a great deal of future investigation to elucidate the actual number of species that belong in this genus.|
|Red List Category & Criteria:||Vulnerable A2d+3cd+4cd ver 3.1|
|Assessor/s:||Dudley, S.F.J, Kyne, P.M. & White, W.T.|
|Reviewer/s:||Cavanagh, R.D., Fowler, S.L. & Compagno, L.J.V. (Shark Red List Authority)|
A large (to 150 cm disc width) inshore batoid with a widespread distribution in the Indo-West Pacific from South Africa to Southeast Asia and north to Japan. Although widespread little is known of the species? biology. Current data and the large size at birth suggest that fecundity is likely to be only 1?2 pups. Rhinoptera javanica occurs in coastal inshore waters in depths less than 30 m, including estuarine and brackish waters, where fishing pressure is typically very heavy and unregulated, especially in Southeast Asian waters. The species? behaviour and inshore occurrence make it highly susceptible and available to a wide variety of fishing gear (beach seine, gillnet, purse seine, benthic longline, trawl etc.). Catch data are scant, but it is landed and marketed in various countries across its range and it is likely to form a component of inshore artisanal fisheries throughout most of its distribution. The degree to which further pressures on the inshore environment throughout Asia (pollution, development, habitat loss etc.) are affecting this species? habitat are uncertain.
The small litter size, its tendency to form large schools, its inshore and estuarine habitat and hence availability to a wide variety of inshore fishing gear, its marketability and the generally intense and unregulated nature of inshore fisheries raises concerns for the conservation status of this species and, despite a lack of species-specific catch data, declines are inferred across its range, warranting a global Vulnerable assessment. With further information the species? population status may prove to be stable in some parts of its range (for example, South Africa, although this represents only a tiny portion of the species? area of occurrence at the western extremity of its range), however, current and future fishing pressure over large parts of species? distribution can result only in serious population declines for this highly susceptible species with a very low intrinsic potential for recovery following overexploitation.
|Range Description:||Complete geographic range is not well defined, but the species is widespread throughout the Indo-West Pacific from South Africa to Japan.|
Native:China; India; Indonesia; Japan; Madagascar; Malaysia; Mozambique; Pakistan; Philippines; Seychelles; Somalia; South Africa (Eastern Cape Province, KwaZulu-Natal); Sri Lanka; Taiwan, Province of China; Tanzania, United Republic of; Thailand
|FAO Marine Fishing Areas:||
Atlantic – southeast; Indian Ocean – eastern; Indian Ocean – western; Pacific – northwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||There is no information available on abundance or population structure.|
|Habitat and Ecology:||
Inshore over continental and insular shelves. Recorded in muddy areas and shallow estuaries (Compagno et al. 1989), and in coastal bays and mangroves (Hennemann 2001). A schooling species; reportedly forms large schools of as many as 500 individuals (Michael 1993). Aplacental viviparous with breeding reported in Japan in late summer and autumn (Michael 1993). Attains 150 cm DW with the largest recorded embryo 63 cm DW (W. White unpubl. data). Although rhinopterids are documented as having 1 to 6 young, this species most likely has 1 to 2 young per litter due to the large size at birth. Rhinopterids are generally highly migratory.
Catches taken in the protective shark nets off the beaches of KwaZulu-Natal, South Africa, peak from March to June (65% of the total annual catch), although the species is caught throughout the year (Young 2001). Overall sex ratio 1:0.39 (M:F) (which differs from unity), modal size 70.1 to 80 cm DW, median male size 75 cm DW and female 70 cm DW (Young 2001). Catches are rare in the southern part of the netted region, which is probably a consequence of lower water temperatures (Young 2001).
Thought to make daily inshore migrations to feed (Last 1997) and food includes clams, oysters and crustaceans (Michael 1993).
Life history parameters
Age at maturity (years): Unknown.
Size at maturity (disc width): Unknown (female); >100 cm DW, males at 97 cm DW not yet fully mature (W. White, unpubl. data) (Indonesia).
Longevity (years): Unknown.
Maximum size (disc width): 150 cm DW (Compagno 1988).
Size at birth: one late term embryo was 63 cm DW (W. White, unpubl. data) (Indonesia).
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: 1 to 6 pups/litter (Last 1997), but probably mostly 1 to 2.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.
Details of catches of this species throughout its range are scant. Nevertheless its small litter size, its tendency to form large schools, its inshore habitat and hence availability to a wide variety of inshore fishing gear (beach seine, gillnet, purse seine, benthic longline, trawl etc.), its marketability and the generally intense and unregulated nature of inshore fisheries across most of the species? range warrant a global listing of Vulnerable.
This species occurs in coastal inshore waters in depths of less than 30 m where fishing pressure is typically very heavy, especially in SE Asian waters. The strong swimming nature of this species makes it quite susceptible to a range of fisheries, especially inshore gill net fisheries which are extremely intensive in some regions (for example, Kalimantan in Indonesia). Rhinopterids are also known to inhabit estuarine areas where fishing pressure is also extremely high and where (in SE Asia at least) pollution is also a major factor for all marine life.
The species is likely to contribute substantially to numerous inshore artisanal fisheries across its range. Rhinopterids are regularly landed where they are taken. In Southeast Asia, Rhinoptera javanica is known to be landed in Indonesia (W. White unpublished data), Thailand (Vidthayanon 2002), the Philippines (Compagno et al. 2005), Taiwan (P. Kyne pers. obs.) and Sabah, Malaysia (Manjaji 2002), all of which are countries where fishing pressure on the inshore environment is intense and generally unregulated. The species is probably widely utilized across its range (Compagno and Last 1999) due to its availability to fisheries. Fishing pressure on the inshore environment across most of the species? range is only likely to increase in the future.
In South Africa, Rhinoptera javanica contributed 8.9% to the total batoid catch taken between 1981 and 2000 in the protective shark nets off KwaZulu-Natal, South Africa (Young 2001). Of the mean annual catch of 31 animals, 59% were released alive. Catches peaked between 1988 and 1990 but there was no overall trend in catch or catch rate. Rhinoptera javanica is taken as bycatch in the shallow-water trawls (20?30 m) of a prawn trawl fishery that operates off central KwaZulu-Natal (Marine and Coastal Management, unpubl. data).
The species is not common in Tanzanian fisheries but is caught in artisanal beach seines, bottom set gillnets and demersal trawls (Bianchi 1985). It has not been recorded in Madagascan fisheries (Andrew Cooke, Madagascar Sharks Group, Antananarivo and Lyn Robinson, WWF Madagascar, Antsiranana, pers. comm., September 2003).
There is no existing legislation specifically for this species. Fisheries taking R. javanica (directed or bycatch) are generally unmanaged throughout the species? range. Attempts to monitor and regulate fisheries in these regions would greatly improve conservation of this and other chondrichthyans. Monitoring (including species-specific catch details) of any directed elasmobranch landings and bycatch across the Indo-West Pacific are necessary to provide valuable information on the biology and population status of these rays. Fishery-independent surveys of this and other elasmobranchs are necessary to provide estimates of abundance and biomass.
In addition to species-specific catch details, life history information including age, growth, longevity, movement patterns, habitat use, potential nursery areas, diet, and further reproductive studies are necessary to develop effective conservation actions for R. javanica. Direct estimates of fishing and natural mortality are critical for assessing fisheries impacts on a particular species. Tagging, tracking, and genetic studies are essential for determining the population structure, movement patterns, and possible subpopulations throughout the species? range, as well as the resolution of its phylogenetic relationship to other Rhinoptera spp.
A recent reduction in the number of protective shark nets off KwaZulu-Natal, South Africa will help to limit catches in that region. The recreational line fishery in South Africa is managed by a bag limit of one/species/person/day for unspecified chondrichthyans, which includes R. javanica.
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 R. javanica.
|Citation:||Dudley, S.F.J, Kyne, P.M. & White, W.T. 2006. Rhinoptera javanica. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|
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