Rhizoprionodon acutus, Milk Shark

Transcription

1 The IUCN Red List of Threatened Species ISSN (online) IUCN 2008: T41850A Rhizoprionodon acutus, Milk Shark Assessment by: Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003) View on Citation: Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003) Rhizoprionodon acutus. The IUCN Red List of Threatened Species 2003: e.t41850a Copyright: 2015 International Union for Conservation of Nature and Natural Resources Reproduction of this publication for educational or other non-commercial purposes is authorized without prior written permission from the copyright holder provided the source is fully acknowledged. Reproduction of this publication for resale, reposting or other commercial purposes is prohibited without prior written permission from the copyright holder. For further details see Terms of Use. The IUCN Red List of Threatened Species is produced and managed by the IUCN Global Species Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership. The IUCN Red List Partners are: BirdLife International; Botanic Gardens Conservation International; Conservation International; Microsoft; NatureServe; Royal Botanic Gardens, Kew; Sapienza University of Rome; Texas A&M University; Wildscreen; and Zoological Society of London. If you see any errors or have any questions or suggestions on what is shown in this document, please provide us with feedback so that we can correct or extend the information provided. THE IUCN RED LIST OF THREATENED SPECIES

2 Taxonomy Kingdom Phylum Class Order Family Animalia Chordata Chondrichthyes Carcharhiniformes Carcharhinidae Taxon Name: Rhizoprionodon acutus (Rüppell, 1837) Synonym(s): Carcharias acutus Rüppell, 1837 Common Name(s): English: Taxonomic Source(s): Milk Shark, Fish-shark, Longman's Shark, White-eyed Shark Compagno, L.J.V Carcharhinidae. In: J.-C. Hureau & T. Monod (ed.), Check-list of the Fishes of the North-eastern Atlantic and of the Mediterranean (CLOFNAM). Volume 1, pp Unesco, Paris. 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, Assessment Information Red List Category & Criteria: Least Concern ver 3.1 Year Published: 2003 Date Assessed: April 30, 2003 Annotations: Needs Updating 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 Range Description: This is the most widely distributed species of the genus Rhizoprionodon, occurring from western Africa to southern Japan and northern Australia. 1

3 Country Occurrence: 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 2

4 Distribution Map 3

5 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. Current Population Trend: Unknown Habitat and Ecology (see Appendix for additional information) 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 (see Appendix for additional information) 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 Australian fisheries are managed, but there is no assessment of population status and no speciesspecific regulations. 4

6 Credits Assessor(s): Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003) Reviewer(s): Fowler, S. & Cavanagh, R.D. (Shark Red List Authority) 5

7 Bibliography Anderson, R.C. and Simpfendorfer, C.A Indian Ocean. In: S.L. Fowler, M. Camhi, G.H. Burgess, G.M. Cailliet, S.V. Fordham, R.D. Cavanagh, C.A. Simpfendorfer and J.A. Musick. Sharks, rays and chimaeras: the status of the chondrichthyan fishes. IUCN SSC Shark Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. Bass, A.J., D'Aubrey, J.D. and Kistnasamy, N Sharks of the east coast of southern Africa. V. The families Hexanchidae, Chlamydoselachidae, Heterodontidae, Pristiophoridae and Squatinidae. South African Association for Marine Biological Research, Oceanographic Research Institute Investigational Report No. 43. Compagno, L.J.V FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. FAO Fisheries Synopsis No. 125, Volume 4, Part 1. Devadoss, P Observations on the breeding and development of some sharks. Journal of the Marine Biological Association of India 30: Devadoss, P., Kuthalingam, M.D.K. and Thiagarajan, R The present status and future prospects of elasmobranch fishery in India. CMFRI 44(1): IUCN IUCN Red List of Threatened Species. Downloaded on 18 November IUCN SSC Shark Specialist Group. Specialist Group website. Available at: Kasim, H.M Shark fishery of Verval coast with special reference to population dynamics of Scoliodon laticaudus (Muller and Henle) and Rhizoprionodon acutus (Ruppell). Journal of the Marine Biological Association of India 33: Krishnamoorthi, B. and Jagadis, I Biology and population dynamics of the grey dogshark, Rhizoprionodon (Rhizoprionodon) acutus (Ruppell), in Madras waters. Indian Journal of Fisheries 33: Last, P.R. and Stevens, J.D Sharks and Rays of Australia. Second Edition. CSIRO Publishing, Collingwood. Stevens, J.D Management of shark fisheries in northern Australia. In: R. Shotton (ed.). Case studies of the management of elasmobranch fisheries. pp FAO Fisheries Technical Paper. No. 378, Part I. FAO, Rome. Stevens, J.D. and McLoughlin, K.J Distribution, size and sex composition, reproductive biology and diet of sharks from northern Australia. Australian Journal of Marine and Freshwater Research 42: Citation Simpfendorfer, C.A. (SSG Australia & Oceania Regional Workshop, March 2003) Rhizoprionodon acutus. The IUCN Red List of Threatened Species 2003: e.t41850a Disclaimer To make use of this information, please check the Terms of Use. 6

8 External Resources For Images and External Links to Additional Information, please see the Red List website. 7

9 Appendix Habitats ( Habitat Season Suitability Major Importance? 9. Marine Neritic -> 9.1. Marine Neritic - Pelagic - Unknown Marine Oceanic -> Marine Oceanic - Epipelagic (0-200m) - Unknown - Threats ( Threat Timing Scope Severity Impact Score 5. Biological resource use -> 5.4. Fishing & harvesting aquatic resources -> Unintentional effects: (subsistence/small scale) 5. Biological resource use -> 5.4. Fishing & harvesting aquatic resources -> Unintentional effects: (large scale) Ongoing Stresses: 2. Species Stresses -> 2.1. Species mortality Ongoing Stresses: 2. Species Stresses -> 2.1. Species mortality 8

10 The IUCN Red List Partnership The IUCN Red List of Threatened Species is produced and managed by the IUCN Global Species Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership. The IUCN Red List Partners are: BirdLife International; Botanic Gardens Conservation International; Conservation International; Microsoft; NatureServe; Royal Botanic Gardens, Kew; Sapienza University of Rome; Texas A&M University; Wildscreen; and Zoological Society of London. THE IUCN RED LIST OF THREATENED SPECIES