It seems unlikely that the Australian red claw clayfish will establish reproductive populations under Norwegian climate conditions, but hitchhiker organisms and infectious agents could potentially follow the import, and unless managed, may pose risks to biodiversity and aquatic animal health. This is the conclusion in a risk assessment from the Norwegian Scientific Committee for Food Safety (VKM).
The Norwegian Food Safety Agency (NFSA) and the Norwegian Environment Agency requested the Norwegian Scientific Committee for Food Safety (VKM) for an opinion of risks, with regards to aquatic animal health and biodiversity in Norwegian fauna, associated with import of Australian redclaw crayfish (Cherax quadricarinatus) to Norway for aquaculture.
The Australian red claw crayfish is a relatively large freshwater crayfish, originating in tropical Australia and Papua New Guinea. Redclaw is considered an invasive alien species, but has a limited tolerance for low temperatures. It seems unlikely that redclaw can establish reproductive populations under Norwegian climate conditions.
However, there are concerns of negative impacts on native fauna if redclaw should manage to escape in high numbers. Hitchhiker organisms and infectious agents could potentially follow the import, and unless managed, may pose risks to biodiversity and aquatic animal health.
Four disease-causing agents
Four disease-causing agents were identified as hazards: Cherax quadricarinatus Bacilloform Virus (CqBV), White Spot Syndrome Virus (WSSV), the oomycete Aphanomyces astaci and the fungus Batrachochytrium dedrobatidis (BD). Redclaw or related crayfish species can be infected or act as carriers of these pathogens.
The risk associated with the introduction of WSSV is considered as high, with some uncertainty related to the effect of WSSV on Norwegian crustaceans under natural water temperature conditions.
Crayfish plague is already established in Norway in a few areas. Since Aphanomyces astaci, the agent that causes crayfish plague, may be transferred to areas that are plague-free, the risk of spreading crayfish plague through import of redclaw is considered as high in the absence of specific measures.
BD occurs all over Australia and Asia, and has also reached Africa, America and parts of Europe, but is still not reported in Norway. Amphibian species are declining at an alarming rate globally due to BD. The risk of introducing BD with redclaw from an endemic area is considered as high in the absence of specific measures.
The risk associated with the introduction of CqBV with imported redclaw is considered as extremely low, with some uncertainty related mainly to the unknown, although unlikely, susceptibility of Norwegian crustaceans to the disease.
There are very few ecological studies of tropical species under temperate environments available, making predictions on consequences of reproductive ability and establishment of redclaw in Norwegian conditions difficult. VKM also recognizes a number of uncertainties and data gaps related to health risks.
The risk assessment is conducted by a working group comprising members from the Panel on Animal Health and Welfare, the Panel on Alien Organisms and trade in endangered species (CITES) and the Panel on Microbial Ecology and external experts from the Norwegian Veterinary Institute.