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Rhizoprionodon acutus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES CARCHARHINIFORMES CARCHARHINIDAE

Scientific Name: Rhizoprionodon acutus
Species Authority: (Rüppell, 1837)
Common Name(s):
English Milk Shark, Fish-shark, Longman's Shark, White-eyed Shark
Synonym(s):
Carcharias acutus Rüppell, 1837
Taxonomic Notes: Synonyms = Carcharias (Prionodon) sorrakowa Bleeker, 1853; Carcharias (Scoliodon) walbeehmi Bleeker, 1856; Carcharias (Scoliodon) crenidens Klunzinger, 1879; Carcharias aaronis Hemprich & Ehrenberg, 1899; Scoliodon longmani Ogilby, 1912; Scoliodon vagatus Garman, 1913; Carcharias eumeces Pietschmann, 1913.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2003
Date Assessed: 2003-04-30
Annotations:
Needs updating
Assessor(s): Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003)
Reviewer(s): Fowler, S. & Cavanagh, R.D. (Shark Red List Authority)
Justification:
Rhizoprionodon acutus is a common wide spread species (the most widespread of this genus) that occurs from west Africa to the western Pacific (southern Japan). It is a coastal species, and as such it is commonly taken in a wide range of artisanal, subsistence and commercial fisheries and regularly seen in fish markets. Despite its widespread occurrence in fisheries and the limited data available about their impacts on populations, it is assessed as Least Concern due to its wide distribution and relatively productive life history.

Geographic Range [top]

Range Description: This is the most widely distributed species of the genus Rhizoprionodon, occurring from western Africa to southern Japan and northern Australia.
Countries:
Native:
Angola (Angola); Australia (New South Wales, Northern Territory, Queensland, Western Australia); Bahrain; Bangladesh; Benin; Brunei Darussalam; Cambodia; Cameroon; China; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Djibouti; Egypt; Equatorial Guinea; Eritrea; Gabon; Gambia; Ghana; Guinea; Guinea-Bissau; India; Indonesia; Iran, Islamic Republic of; Japan; Kenya; Kuwait; Liberia; Madagascar; Malaysia; Mauritania; Mozambique; Myanmar; Nigeria; Oman; Pakistan; Papua New Guinea; Philippines; Portugal (Madeira); Qatar; Sao Tomé and Principe; Saudi Arabia; Senegal; Sierra Leone; Singapore; Somalia; South Africa; Sri Lanka; Sudan; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Togo; United Arab Emirates; Viet Nam; Yemen
FAO Marine Fishing Areas:
Native:
Atlantic – eastern central; 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 [top]

Population: The section of the population in western Africa is geographically isolated from the remainder of the population. There are no data on the population numbers in any part of the range.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: A common continental shelf species. They are born at 35 to 40 cm in Australia and 25 cm in Africa, and mature at approximately 75 cm. Australian animals reach a maximum of around 100 cm, while African animals reach a larger size possibly as high as 178 cm (Last and Stevens 1994). They are viviparous, with litter sizes from one to eight (Compagno 1984). The gestation period is about 12 months, and mature females produce young every year. In Australian waters reproduction is asynchronous (Stevens and McLoughlin 1991), but in African and Asian waters reproduction is seasonal (Bass et al. 1975, Devadoss 1988). R. acutus reaches maturity after two or three years and probably lives to a maximum of at least eight years (Compagno 1984). These life history parameters suggest a relatively high productivity that would sustain a reasonable level of fishing pressure, although not as high as that sustained by R. oligolinx or R. taylori.
Systems: Marine

Threats [top]

Major Threat(s): Rhizoprionodon acutus is an abundant inshore shark that is commonly caught in subsistence, artisanal and commercial fisheries throughout its range. Catches in fisheries are best documented in Australia and India. In northern Australia it is one of the most commonly taken shark species in fish and prawn trawls (Last and Stevens 1994). It also represents 2% of the catch in gillnets and 6% of the catch on longlines (Stevens 1999). Despite these catches the Australian population does not appear to have been adversely affected.

In Indian waters it is commonly taken gillnet and trawl fisheries (Devedoss et al. 1989). There are a number of studies in Indian waters that have assessed the status of the population based on demographic approaches. Krishnamoorthi and Jagadis (1986) estimated that in Madras waters R. acutus was being under-exploited. Kasim (1991) estimated that along the Verval coast that the species was being fished below its maximum sustainable level, with males fished more heavily than females. The results of these assessments are questionable as they applied simplistic teleost based methods. As such the results are treated with caution. Since these assessments were undertaken the Indian elasmobranch catch has increased dramatically (Anderson and Simpfendorfer, in press) and this species is likely to have become more heavily exploited.

Data from other areas is limited. It is known to be landed in other countries, but there is no other data available on the status of populations or fisheries.

Conservation Actions [top]

Conservation Actions: Australian fisheries are managed, but there is no assessment of population status and no species-specific regulations.

Citation: Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Rhizoprionodon acutus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 26 July 2014.
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