|Scientific Name:||Ptychochromis oligacanthus (Bleeker, 1868)|
Ptychochromis nossibeensis Bleeker, 1868
|Taxonomic Notes:||Specimens of Tilapia oligacanthus Bleeker, 1868 from Lake Pambilao, Madagascar are described as var. nossibeensis. Valid as Ptychochromis oligacanthus (Bleeker, 1868).|
|Red List Category & Criteria:||Endangered B1ab(iii) ver 3.1|
|Assessor(s):||Ravelomanana, T. & Sparks, J.S.|
|Reviewer(s):||Raminosoa, N., Randrianizahaisa, H., Rasoloariniaina, R & Velosoa, J.|
|Contributor(s):||Loiselle, P.V. & Participants of the CBSG/ANGAP CAMP "Faune de Madagascar" workshop, Mantasoa, Madagascar 2001|
This species is endemic to Madagascar and consists of many disjunct subpopulations in rivers and crater lakes with an overall estimated extent of occurrence (EOO) of 3,575 km2. The subpopulations on Nosy Be are in good condition and are stable at present but invasive species represent a plausible threat and if introduced, could result in each of these subpopulations becoming non-viable. The subpopulations on the mainland are already under threat due to ongoing habitat loss and overfishing. Although these subpopulations are larger these threats could push the species towards local extinction. As there is no genetic exchange between these subpopulations, the population is considered to be severely fragmented. Therefore, this species is assessed as Endangered.
|Previously published Red List assessments:|
|Range Description:||This species is restricted to freshwater habitats of northwestern Madagascar, from the Sambirano River northward to the Mananjeba drainage (Andranomaloto River), and including the crater lakes of Nosy Be (Stiassny and Sparks 2006). The type locality of Ptychochromis oligacanthus is the crater lake, Lac Pambilave (Lake Ampombilava) in Nosy Be (Bleeker 1868).|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Whereas subpopulations on Nosy Be appear to be stable for the time being (Loiselle 2005), mainland subpopulations are threatened by rampant deforestation and habitat degradation or destruction throughout their range. Diversion of water for large-scale irrigation projects poses a particular threat to the subpopulations of this species in the basins of the Mananjeba and the Mahavavy du Nord (Stiassny and Sparks 2006).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
Ptychochromis oligacanthus is generally inhabits lakes and rivers. In Nosy Be, the lakes are pristine. In Madagascar mainland, the lakes are generally disturbed, the water is turbid and the bottom is dominated by silt and sand (T. Ravelomanana, unpublished data).
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Movement patterns:||Not a Migrant|
|Use and Trade:||Fisheries activity is generally for local trade or consumption.|
The mainland subpopulations are threatened by habitat loss and overfishing using large seine net with small mesh (T. Ravelomanana pers. obs. 2016). Those subpopulations in the many crater lakes have no major threats at present but introduction of invasive species is a potential future threat.
|Conservation Actions:||No real conservation measures in place, however, the crater lakes on Nosy Be receive some protection due to local customs (e.g. fishing only with hook and line, or large crocodile populations; J. Sparks pers. obs.). The Nosy Be crater lakes are now within the protected area managed by "l homme et l'environnement".|
|Citation:||Ravelomanana, T. & Sparks, J.S. 2016. Ptychochromis oligacanthus. The IUCN Red List of Threatened Species 2016: e.T18830A58300256.Downloaded on 21 June 2018.|
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