ALIEN FRESHWATER CRUSTACEAN AND INDIGENOUS MOLLUSC SPECIES WITH AQUACULTURE POTENTIAL IN EASTERN AND SOUTHERN AFRICA

Summary

Farming of crustaceans and molluscs in Southern Africa is not well developed, but it is likely to intensify in coming years. The pressure to introduce new candidate species to satisfy specific culinary demands or improve bulk yields and efficiencies is also expected to increase.

This paper stresses some of the problems associated with the intentional or accidental introduction of exotics, and translocation of local species into catchments where they did not previously occur.

Several freshwater crustacean species have already been introduced into eastern and southern Africa, often without the knowledge and permission of the authorities. Introduced freshwater crayfish constitute a new element of African fauna, as such species were not present in the continent originally. Introduced species from North America and Australia could thus be seen as using some aspect of the resources which are under-utilized by existing species in Africa. This paper, however, argues that introduced species are likely to cause ecological imbalances with rapid and dramatic consequences.

Possible solutions to minimize the ecological impact of farming crustaceans and molluscs are listed at the end of the paper. As experience has shown that animals will usually escape the confines of a facility, the introduction of aquatic organisms for aquaculture should be considered as a purposeful introduction into the wild, even though the quarantine or hatchery facility may be a closed system. Therefore, a strict precautionary approach would not permit deliberate introduction and allow strong measures to prevent unintentional introductions.

In order to minimize the risk of unintentional importation of parasites, pathogens and associated species such as snails, there is an urgent need for better control over the extensive trade in freshwater aquatic plants, ornamental aquarium fish and crayfish species.

Keywords:

• Aliens
• indigenous
• aquaculture potential
• animal transfer and diseases