|Scientific Name:||Rhinobatos irvinei|
|Species Authority:||Norman, 1931|
|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:||Vulnerable A4bd ver 3.1|
|Assessor(s):||Séret, B. & Valenti, S.V.|
|Reviewer(s):||Cavanagh, R.D. & Fowler, S.L. (Shark Red List Authority)|
The Spineback Guitarfish (Rhinobatos irvinei ) is known from Morocco to southern Angola, along the western Africa coast, in shallow waters to ~30 m depth. It is captured by bottom trawls, trammelnets and hook-and-line fisheries, like other rhinobatids in this region. Inshore fishing pressure is intensive throughout much of its range along the western coast of Africa and rhinobatids are particularly valued for their fins. The species' preference for coastal, inshore waters renders it vulnerable to the effects of habitat degradation and destruction through coastal development, pollution and mangrove deforestation. Significant areas of mangrove forest have been destroyed in areas of the Gulf of Guinea, possibly removing important nursery grounds for this species. Although no specific data are available on population trends or capture in fisheries and this species was never known to be abundant, observations indicate that it is caught on an increasingly rare basis. Other Rhinobatos species have proved vulnerable to population depletion as a result of their limiting life-history characteristics and serious declines have been reported in similar species where they face similar threats. Given its susceptibility to capture by multiple gear types, intensive fishing pressure across its inshore range, the high value of its fins, widespread destruction of its coastal habitat and insight from similar species a precautionary assessment of at least Vulnerable is warranted globally on the basis of inferred population declines.
|Range Description:||Eastern central and southeast Atlantic: Morocco to southern Angola (Séret in press). A record from Namibia requires confirmation (Séret in press).|
Native:Angola (Angola); Benin; Cameroon; Congo; Congo, The Democratic Republic of the; Côte d'Ivoire; Equatorial Guinea; Gabon; Ghana; Guinea; Guinea-Bissau; Liberia; Mauritania; Morocco; Nigeria; Senegal; Sierra Leone; Togo; Western Sahara
|FAO Marine Fishing Areas:|
Atlantic – eastern central; Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||It has never been abundant but nowadays it has become evidently rare, taken in fisheries on an increasingly rare basis (B. Séret pers. obs. 2008).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||An inshore guitarfish occurring in shallow coastal waters to about 30 m depth (Séret in press). Maximum size is 100 cm total length (TL) and the species commonly reaches 60-66 cm TL (Séret in press). Males mature at about 42 cm TL. Ovoviviparous with litters of 1-3 pups. Feed on benthic invertebrates mainly shrimps (Séret in press).|
This species is captured by bottom trawls, trammelnets and hook-and-line, like other rhinobatids in this region. It is taken as bycatch in such fisheries throughout its range. Inshore fishing pressure is intensive throughout its range along the western coast of Africa. The small-scale fisheries that originally exploited elasmobranchs off western Africa in the 1950s have undergone huge development during the past 20 years in terms of numbers of boats and improvement of gear. Interviews with fishermen and traders strongly suggest that the shark fin trade is financing the overexploitation of shark resources and leading to declining catches throughout Africa (WildAid 2001, Walker et al. 2005). Rhinobatos species are particularly valued for their fins, which fetch high prices in the shark fin trade (CITES Animals Committee 2006). The targeting of these species for their fins has already led to population declines in several similar species of elasmobranchs (including R. cemiculus and R. rhinobatos), the extirpation of some Pristis species, and a significant transformation in the structure of small-scale fisheries (Walker et al. 2005). Extensive coastal shrimp trawl fisheries for pink shrimp Paenus notialis are also known to operate off Cameroon and Benin (IGGC 2007b). This species is likely taken as bycatch of these and other trawl fisheries that operate within its inshore range.
As well as over-exploitation by fisheries, this species coastal habitat is threatened by degradation and destruction through coastal development, pollution (residential, agricultural, hydrocarbon and heavy metals) and mangrove deforestation (IGGC 2007a,b). In Ghana, 55% of the mangroves and significant marshlands around the greater Accra area has been destroyed through pollution and overcutting. In Benin, the figure is 45% in the Lake Nouake area, in Nigeria, 33% in the Niger Delta, in Cameroon, 28% in the wouri Estuary and in Côte d'Ivoire, about 60% in the bay of Cocody (IGGC 2007b).
Serious declines have been documented in other Rhinobatos spp where they are heavily fished. These include, Rhinobatos rhinobatos and R. cemiculus which occur in the Mediterranean Sea along the western African coast, and are both assessed as Endangered, based on observed and inferred population declines as a result of targeted and incidental fishing pressure.
There are no known conservation measures in place for this species.
Recommended: Efforts should be made to quantify catch levels and determine population trends, which will require capacity-building, education and training programmes. Measures to protect and restore this species habitat would also be beneficial, such as identification and management of Marine Protected Areas to conserve nursery grounds. Research is needed on the species' life-history characteristics.
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 management of all elasmobranch species in the region.
A seasonal ban on the targeted exploitation of this species elsewhere within the West African region would decrease the rate of capture of reproductively active individuals (M. Ducrocq pers. comm. 2006). A ban on finning and the dumping of carcasses should be considered, as this would represent the most effective method of decreasing the fishing pressure on this species. Otherwise, the implementation of licences for targeted and non targeted shark fishing and finning and a tax system on shark fins are recommended as measures to control the fishing pressure impacting this species.
|Citation:||Séret, B. & Valenti, S.V. 2009. Rhinobatos irvinei. The IUCN Red List of Threatened Species 2009: e.T161409A5417520.Downloaded on 28 June 2017.|