A Review of Freshwater Crayfish Introductions in Africa

This review summarizes and analyses information on freshwater crayfish introductions in Africa. A total of 136 research papers and reports were found to be relevant. Forty-eight percent reported presence; 21% described negative impacts; 11% referred to potential socio-economic benefits; 9% evaluated control measures; 6% documented co-introduced parasites. Out of nine introduced crayfish species, five species <i>Astacus astacus</i>, <i>Cherax quadricarinatus</i>, <i>Faxonius limosus</i>, <i>Procambarus clarkii</i>, and <i>Procambarus virginalis</i> have established populations in the wild. <i>Astacus astacus</i> and <i>F. limosus</i> are present only in Morocco and <i>P. virginalis</i> is limited to Madagascar. <i>Cherax quadricarinatus</i> and <i>P. clarkii</i> have established populations in five and six countries, respectively. The main driver of crayfish introductions was to provide socio-economic benefits through aquaculture and fisheries development but there is limited evidence of success. Prevailing negative socio-economic impacts are linked to damage to agricultural water infrastructure, damage to fishing gear and declining fisheries performance. Ecological impacts pertain to direct and multi-trophic consumptive effects as well as indirect competitive effects primarily upon macro-invertebrates and potential spillover of parasites to other decapods. Research priorities are determining abundance, distribution and spread of crayfishes and assessing ecological impact to inform management decisions.