Avoiding the introduction of exotic pathogens with Atlantic Salmon Salmo salar reared in British Columbia

Seawater netpen culture of salmonid fishes is an important aquaculture enterprise in British Columbia (B.C.), and about 70% of the approximate 50,000 metric tons (MT) annual netpen production in B.C. is Atlantic salmon (Salmo salar). Commercial production of Atlantic salmon in B.C. began in the mid-1980s. As with many other forms of aquaculture, the industry initially relied on the importation of eggs from other areas, and thus Fisheries and Oceans Canada developed specific quarantine and inspection policies to prevent the introduction of exotic pathogens with these transfers. In brief, regarding the source of eggs, the "Policy for the Importation of Atlantic Salmon into British Columbia" requires that (a) all importations must comply with the Canadian Fish Health Protection Regulations, (b) only surface-disinfected eggs are allowed into B.C. (no live salmonids allowed), (c) eggs must originate from broodstock held in captivity for at least one generation, and (d) the source facility does not have salmonid diseases exotic to B.C. A facility receiving eggs must hold eggs and progeny under certain strict quarantine conditions, which include disinfection of effluent from the holding facilities and discharge to ground until fish are 3 g. The fish are also held in isolation until introduced to seawater netpens. In addition, fish are examined regularly for diseases before release. Initially, several companies imported eggs for production. Now that most companies have efficient broodstock programs within B.C., very few import permits are issued. Several previously unrecognized diseases, or different manifestations of Pacific salmon (Oncorhynchus spp.) diseases, have been observed in Atlantic salmon reared in seawater netpens in B.C. None of these diseases, however, have been attributed to introduction of exotic pathogens. Considering that close to 23 million Atlantic salmon eggs have been imported into B.C. in the last 10 years or so, this approach has been successful at avoiding the introduction of exotic pathogens into B.C. with this valuable industry. One critical component that has contributed to this success is the "eggs only" policy of B.C., which has avoided introduction of many pathogens that require a live salmonid fish host.