|Scientific Name:||Rhynchobatus luebberti Ehrenbaum, 1915|
Rhynchobatus atlanticus Regan, 1915
|Taxonomic Source(s):||Last, P.R., Séret, B. and Naylor, G.J.P. 2016a. A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea). Zootaxa 4117(4): 451-475.|
|Red List Category & Criteria:||Endangered A2ad+3d+4ad ver 3.1|
|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)|
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%.
|Range Description:||West coast of Africa from Mauritania through the Gulf of Guinea south to Angola.|
Native:Angola; Benin; Cameroon; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Equatorial Guinea; Gabon; Gambia; Ghana; Guinea; Guinea-Bissau; Liberia; Mauritania; Nigeria; Senegal; Sierra Leone; Togo
|FAO Marine Fishing Areas:|
Atlantic – southeast; Atlantic – eastern central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species was historically moderately abundant in the 1960s but populations are declining markedly in areas throughout its range that are heavily fished.|
|Current Population Trend:||Decreasing|
|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.
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.
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).
|Citation:||Compagno, L.J.V. & Marshall, A.D. 2006. Rhynchobatus luebberti. The IUCN Red List of Threatened Species 2006: e.T60180A12303076.Downloaded on 20 October 2017.|
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