Disease implications associated with the use of exotic species in aquaculture.
Infectious diseases of aquatic animals have caused significant economic losses to the aquaculture industries in many parts of the world. In some cases, the source of the pathogen has not been identified or was associated with non-aquaculture activities such as untreated effluent from fish processing plants, dumping of ballast water by the shipping industry, importation of live aquatic animals and products for the "table" market, and the pet trade. However, other sources of pathogens have been traced to transplanting of stocks and importation of exotic species for aquaculture. In order to reduce and hopefully eliminate the accidental transfer of pathogens resulting from aquaculture activities, various national and international organisations have described guidelines and import risk analysis procedures supported by disease surveillance protocols and tools for aquatic animals. An additional consideration that is more difficult to evaluate in advance of the introduction of an exotic animal for aquaculture is the potential of naturally occurring organisms in the receiving environment being pathogenic to the introduced animal. Also, if such pathogens occur, it is necessary to determine if the farming of the exotic species will magnify the pathogen load and exacerbate the disease problem for indigenous species. As for import risk analysis procedures, the ability to assess this aspect of the subject will be dependant upon the availability of information on the pathogens in the receiving environment and their transmission and host specificity characteristics.