Abstract

The Atlantic salmon farms in eastern Canada and northeastern USA produce more than 20,000 metric tonnes annually. The seawater net pens are prone to the influences of wild fish introducing disease and the inability to alter unfavorable environmental conditions. As a result, the fish farms have experienced three distinct outbreaks of disease since 1992 which have resulted in major production losses. Coldwater vibriosis, a bacterial septicemia caused by Vibrio salmonicida, first occurred in 1993. Although the bacteria was sensitive to available oral antibiotics, the cold temperatures at which the disease occurs is also when fish tend to have dramatically reduced appetites even when healthy. An effective injectable vaccination program was initiated to reduce further losses. Infestations with the crustacean skin parasite, Lepeophtheirus salmonis (sea lice), started in the exceptionally warm summers of 1994 and 1995. These parasites continue to be a major control issue due to the lack of approved pesticides, the possible impact of such treatments on the local environment, and the potential for sea lice to act as vectors for viruses. Infectious salmon anemia virus (ISAv) began causing mortalities in the late summer of 1996. ISAv has caused more than $20 million in losses over a two year period and continues to be a concern for all farmers in the Bay of Fundy. Currently, there is much activity in the development of control measures for this disease as there is anticipation of what is next to hit the area.