Overview

Comprehensive Description

Biology

Occurs in shallow coastal waters, more or less stationary. Ovoviviparous (Ref. 50449).
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Distribution

Range Description

West coast of Africa from Mauritania through the Gulf of Guinea south to Angola.
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Eastern Atlantic: Senegal to Congo. Reported from Mauritania (Ref. 55783).
  • Stehmann, M. 1990 Rhynchobatidae. p. 22. In J.C. Quero, J.C. Hureau, C. Karrer, A. Post and L. Saldanha (eds.) Check-list of the fishes of the eastern tropical Atlantic (CLOFETA). JNICT, Lisbon; SEI, Paris; and UNESCO, Paris. Vol. 1. (Ref. 3685)
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Southeastern Atlantic.
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Physical Description

Size

Maximum size: 3000 mm TL
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Max. size

300 cm TL (male/unsexed; (Ref. 2683))
  • Schneider, W. 1990 FAO species identification sheets for fishery purposes. Field guide to the commercial marine resources of the Gulf of Guinea. Prepared and published with the support of the FAO Regional Office for Africa. Rome: FAO. 268 p. (Ref. 2683)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Restricted inshore coastal habitat. Benthic on soft mud or sand from the intertidal zone to 70 m, but generally not deeper than 35 m. Aplacental viviparous, but no details available of its biology. Given their size, rhynchobatids are suspected to have low fecundity and slow growth rates characteristic of large elasmobranchs. Rhynchobatus djiddensis from the Western Indian Ocean is reported to bear litters of four pups (van der Elst 1988).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length cm): Unknown.
Longevity (years): Unknown.
Maximum size (total length): 300 cm TL.
Size at birth: 52 cm TL.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: Unknown.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Systems
  • Marine
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Environment

demersal; marine, usually ? - 35 m (Ref. 27000)
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Depth range based on 2 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 22 - 33
  Temperature range (°C): 21.232 - 25.158
  Nitrate (umol/L): 1.274 - 8.575
  Salinity (PPS): 34.452 - 35.673
  Oxygen (ml/l): 3.575 - 4.489
  Phosphate (umol/l): 0.348 - 0.600
  Silicate (umol/l): 0.994 - 7.661

Graphical representation

Depth range (m): 22 - 33

Temperature range (°C): 21.232 - 25.158

Nitrate (umol/L): 1.274 - 8.575

Salinity (PPS): 34.452 - 35.673

Oxygen (ml/l): 3.575 - 4.489

Phosphate (umol/l): 0.348 - 0.600

Silicate (umol/l): 0.994 - 7.661
 
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Life History and Behavior

Life Cycle

Exhibit ovoviparity (aplacental viviparity), with embryos feeding initially on yolk, then receiving additional nourishment from the mother by indirect absorption of uterine fluid enriched with mucus, fat or protein through specialised structures (Ref. 50449).
  • Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
A2ad+3d+4ad

Version
3.1

Year Assessed
2006

Assessor/s
Compagno, L.J.V. & Marshall, A.D.

Reviewer/s
Heupel, M.R., Simpfendorfer, C.A., Kyne, P.M. & Cavanagh, R.D. (Shark Red List Authority)

Contributor/s

Justification
Rhynchobatus luebberti is a large (to 300 cm total length) inshore coastal batoid found from the intertidal zone generally to a depth of 35 m. Occurring off the west African coast from Mauritania through the Gulf of Guinea south to Angola, little is known of its biology, but it is suspected to have low fecundity and slow growth rates characteristic of large elasmobranchs. Target fisheries for guitarfish and indirect fisheries catching them as bycatch exist in several countries, and given their inshore habitat and large size they are an easily accessible valuable resource. The African wedgefish is utilised for both its flesh and its highly-valued fins. Worldwide, demands for dried fins for the international fin trade is a factor in the switch from subsistence fisheries to more directed, commercial export fisheries, especially of larger guitarfish, including Rhynchobatus luebberti. Furthermore, the meat of these larger guitarfish is highly sought after in many African nations. Rhynchobatus luebberti was once moderately abundant in some areas of its distribution but is now taken les frequently. Observed declines include those from specialized guitarfish fisheries in Gambia in the 1980s, marked declines in guitarfish populations in Guinnea-Bissau since the 1990s, and dramatic declines in Mauritania. Such regional declines have resulted from often intensive direct and indirect fishing pressure, from coastal commercial and artisanal fisheries including benthic trawling, trammel netting, gill netting, longlining, and hook and line fishing. Marine Reserves in parts of the species' range might provide some relief from fishing pressure in their immediate area; however, management arrangements will need to ensure that fishing restrictions/prohibitions are strictly enforced.

While exact data are unavailable, large declines are known to have occurred throughout this species' range. Exploitation of the marine environment is intense in many parts of coastal West Africa, with the likelihood of increased exploitation as the human population continues to rise and as the demand for fins increases. The restricted inshore habitat, limited life history characteristics, susceptibility to capture in various gear types, and ever growing demand place coastal rhynchobatids amongst the most vulnerable chondrichthyan fishes. An Endangered assessment for R. luebberti is warranted given direct observations of marked declines in several West African nations, and actual and potential levels of exploitation, inferring that declines across its range have exceeded 50%.
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Population

Population
This species was historically moderately abundant in the 1960s but populations are declining markedly in areas throughout its range that are heavily fished.

Population Trend
Decreasing
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Threats

Major Threats
The restricted coastal habitat, limited life history characteristics, susceptibility to capture in various gear types, and ever growing demand place coastal rhynchobatids amongst the most vulnerable chondrichthyan fishes.

Target fisheries for guitarfish and indirect fisheries catching guitarfish as bycatch currently exist in several countries, and given their inshore habitat and large size they are an easily accessible resource. Actual exploitation levels of the marine environment are intense in some parts of coastal West Africa, and there is the potential for increased exploitation as the human population continues to rise in the region, and as the demand for the international fin trade only increases. Rhynchobatus luebberti was once moderately abundant in some areas of its distribution but is now taken much less frequently. Observed declines have included those from specialized guitarfish fisheries in Gambia in the 1980s, marked declines in guitarfish populations in Guinnea-Bissau since the 1990s, and dramatic declines in Mauritania. These regional declines have resulted from often intensive direct and indirect fishing pressure, from coastal commercial and artisanal fisheries including benthic trawling, trammel netting, gill netting, longlining, and hook and line fishing.

Habitat modification/degradation, including to inshore nursery areas, from human activities (fisheries, pollution, coastal impacts) may be affecting this species given its inshore range.
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Endangered (EN) (A2ad+3d+4ad)
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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Management

Conservation Actions

Conservation Actions
No direct conservation actions in place although Marine Reserves in part of its range might provide some relief from fishing pressures in that immediate area. In December 2003, an agreement was signed halting all forms of target fisheries for sharks and rays in the Banc d'Arguin National Park (PNBA) in Mauritania. The future management of the sciaenid fishery will tend to reduce the elasmobranch bycatch by identifying and closing the fishery during those periods and in those zones where the highest levels of such bycatch occurs. The sub-regional plan of action for the conservation and the management of sharks (Mauritania, Senegal, Gambia, Guinea, Guinea-Bissau and Cape Verde Islands) proposes that all their MPAs should become non-fishing zones for elasmobranchs in future years. Indeed, shark fishing is already prohibited in some small sub-regional MPAs: João-Vieira Poilão Marine Turtles National Park (NP), Orango NP, Cacheu Mangal NP and Urok Islands Community Management Area in Guinea-Bissau; Sine Saloum NP, Bamboung Bolon Marine Reserve and Madeleine Islands NP in Senegal (Ducrocq 2004).

Monitoring and documentation of direct and indirect artisanal and commercial catches is required where the species is being fished. Harvest and trade management is needed, including monitoring and control of fin trading activities.

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. Members of the west African Commission Sous-Regionale des Peches (CSRP) (Mauritania, Senegal, Gambia, Guinea, Guinea-Bissau and Cape Verde Islands) have produced a sub-regional shark plan, endorsed by the Sub-Region's Fisheries Ministers and has since proceeded to encourage its Member States to develop their own National Plans in cooperation within the group and progress with this is underway (Anon. 2004).
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: commercial
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Wikipedia

African wedgefish

The African wedgefish, guitarra, Lubbert's guitarfish, or spikenose wedgefish (Rhynchobatus luebberti) is a species of fish in the Rhynchobatidae family. It is found in Angola, Benin, Cameroon, the Republic of the Congo, the Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mauritania, Nigeria, Senegal, Sierra Leone, and Togo. Its natural habitats are shallow seas, coral reefs, estuarine waters, and coastal saline lagoons. It is threatened by habitat loss and poachers。

References[edit]

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