The West African region is home to over 550 species of freshwater fishes (Paugy et al. 2003, Laleye and Entsua-Mensah 2009), with new species still being discovered regularly. These fishes are spread out across 170 genera and 57 families. The West Africa region contains a diversity of ecoregions, which can broadly be broken down into: xeric systems, savannah dry forest rivers, highland and mountain systems, moist forest rivers, floodplains, swamps, and lakes, and large river deltas.
Of the 550-plus species of freshwater fishes in western Africa, only 537 have been assessed at the species level (Laleye and Entsua-Mensah 2009). The following figure from the IUCN"s Western Africa Freshwater Biodiversity Assessment illustrates the threat status based upon IUCN Red List Categories and Criteria, as well as Regional Guidelines.
Table 1: The number of freshwater fish species in each regional Red List Category in the western Africa region (Laleye and Entsua-Mensah 2009).
Just over half of all species fall into the Least Concern category, though over a quarter of all species (26.3%) are in a threatened category (CR, EN, or VU) (Laleye and Entsua-Mensah 2009). The proportion of threatened fishes in this region is more than twice that of freshwater fishes in southern Africa, yet still slightly lower than the rate in eastern Africa (Darwall et al. 2009).
Water pollution, habitat loss due to deforestation, mining, and agriculture are the greatest threats to freshwater fishes in the region (see Figure 1 below).
Figure 1: Percentages of species currently affected by each threat. Note that many species have more than one threat listed and others (particularly LC species) have no threats listed (Laleye and Entsua-Mensah 2009).
These threats to freshwater fishes are closely linked to each other. For example, deforestation takes place to make way for agricultural expansion in the region. More agriculture leads to increased sedimentation, which in turn degrades water quality. Population and economic growth in the region are major drivers of many of the threats facing freshwater fishes.
The highest concentration of threatened species is in the Niger Delta. Other areas with high numbers of threatened species include the upper Cross River in Cameroon. The Pra and Tano rivers in Ghana, the lower Ogun in Nigeria, upper area of coastal rivers in Liberia/southern Guinea/western Cote D"Ivoire, the Moa, Waanje and Siwa rivers in Sierra Leone, and the upper Baffing river in Guinea all contain between six and nine threatened species per grid cell (Laleye and Entsua-Mensah 2009).
As with most conservation work, the support of the people and governments in western African countries is necessary to implement any positive conservation measures. Public awareness campaigns can help educate people on the issues of deforestation. Water quality should be monitored and controlled across the region. Dams are another threat to healthy freshwater fish populations; therefore, managing entities should attempt to restore some natural flow regimes in some cases and construct the proper mechanisms for facilitating fish passage up and down stream of dams in other cases. Lastly, invasive species must be addressed. Aquatic weeds in rivers, and particularly invasive alien species, can harm freshwater fish populations. Some form of control, be it manual, chemical, or biological would help to restore the ecosystem to one more suitable for maintaining abundant freshwater fish levels.
Darwall, W.R.T., Smith, K.G., Tweddle, D. and Skelton, P. 2009. The status and distribution of freshwater biodiversity in southern Africa. Gland, Switzerland: IUCN and Grahamstown, South Africa: SAIAB.
Laleye, P., and Entsua-Mensah, M. 2009. Freshwater fishes of western Africa. In: Smith, K.G., Diop, M.D., Niane, M. and Darwall, W.R.T. (Compilers). 2009. The Status and Distribution of Freshwater Biodiversity in Western Africa Gland, Switzerland and Cambridge, UK : IUCN. x+94pp+4pp cover.
Paugy D., L√©v√™que C., Teugels G.G. 2003. Poissons d"eaux douces et saum√¢tres de l"Afrique de l"Ouest [The Fresh and Brackish Water Fishes of West Africa]. Tome 1 et 2 IRD. Editions, coll. Faune et Flore tropicales 40, 1272 pp.
Smith, K.G., Diop, M.D., Niane, M. and Darwall, W.R.T. (Compilers). 2009. The Status and Distribution of Freshwater Biodiversity in Western Africa Gland, Switzerland and Cambridge, UK : IUCN. x+94pp+4pp cover.