ScienceAsia 32 (2006): 215-221 |doi: 10.2306/scienceasia1513-1874.2006.32.215

The Special Danger of Viral Pathogens in Shrimp Translocated for Aquaculture

Timothy W. Flegel^*

 
ABSTRACT: It is well known that the majority of invasive aquatic species have been established in new habitats as a result of intentional importation for aquaculture or recreational purposes. This includes shrimp and other crustaceans. As a result of unexpected difficulties that arose from some of these importations, the International Council for Exploration of the Seas (ICES) proposed a set of precautionary guidelines to follow to reduce risks associated with translocations. Briefly, these include preparation of a proposal to the ICES indicating the purpose and area of transfer and detailed biology of the transfer species, and preparation of a detailed impact analysis including environmental disease and socioeconomic issues. In the event that a decision is made to proceed with the introduction, a number of precautionary actions are recommended. For fish, it is recommended that eggs or fry be imported to strict quarantine (including disinfected effluents) and monitored until reared to broodstock size for freedom from disease, before a preliminary phase of limited distribution of their offspring to aquaculture facilities. If broodstock are imported, it is recommended that they be destroyed after spawning (for detailed pathogen assay) and that the offspring be raised and used similarly to the above. After one year of trouble-free, limited field tests, wider use or introduction to open waters may be initiated. For species that are part of commercial practice, abbreviated guidelines are recommended that include export and quarantine procedures. These guidelines are appropriate for vertebrate species (from fish to mammals), but not for shrimp, other crustaceans and arthropods in general, especially with respect to viral pathogens. This is because grossly healthy arthropods tend to carry cryptic viruses (possibly unknown) that can jump to endemic arthropod species and cause massive mortalities. This phenomenon has resulted in 3 major shrimp epizootics that have caused economic losses in the order of several billion US$ since the early 1990’s. To avoid future repetition of this scenario, it is strongly recommended that the ICES guidelines be specifically modified for crustacean introductions to include, during the quarantine period, mandatory cohabitation studies with economically or ecologically important native crustaceans.

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Centex Shrimp and National Center for Genetic Engineering and Biotechnology, Chalermprakiat Building, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand.

* Corresponding author, E-mail: sctwf@mahidol.ac.th

Received 3 Feb 2006, Accepted 29 Mar 2006