Introduction of alien species/strains and their impact on biodiversity

Africa has been the source of alien species that are widely used in aquaculture and fisheries in many parts of the world, but African aquaculture has not benefited greatly either from the domestication of African species or the introduction of improved breed from elsewhere. In efforts to develop African aquaculture further, there is a desire to reintroduce genetically improved tilapia (primarily Oreochromis niloticus) back into Africa. However, there are risks to native African aquatic biodiversity that must be dealt within the re-introduction of African species. Analyzing these risks in order to make informed decisions will require, inter alia, information; such an information source exists in the FAO Database on Introductions of Aquatic Species (DIAS, /statist/fi soft/dias/index.htm). An examination of DIAS revealed that 139 species from 87 genera have been introduced into 42 African countries. Most of these introductions were fi nfi sh (79 per cent). However, 7 per cent were molluscs and 9 per cent were crustaceans. Tilapia is the most important species of fi sh that Africa has contributed to world fi sheries and aquaculture. FAO Fishery statistics reveal that tilapias are farmed in 61 countries outside of Africa (33 in Africa) and these alien tilapia account for 2 per cent of the world aquaculture production. In Africa, tilapia accounts for about 40 per cent of the aquaculture production. The impacts from tilapia introductions vary greatly. The information on the impacts of the introduction is poor, but tilapia introductions into Africa had positive socio-economic benefi ts. There were not many adverse ecological impacts reported in Africa, in spite of the indication that most of the introductions led to self-sustaining populations. Developers concerned with both food security and conservation will need to collect information such as that contained in DIAS, process this into knowledge so that informed decisions can be made, and then develop the wisdom to know when and where to make decisions for the greater good of this and future generations.


Bartley, D.M., Marttin, F. (2004)
Use of genetically improved and alien species for aquaculture and conservation of aquatic biodiversity in Africa