Risk factors for skin lesions in Atlantic salmon, Salmo salar L.

Risk factors for skin lesions observed on the slaughter line in Atlantic sa lmon, Salmo salar L., were examined in a cohort study in Hordaland County, Norway. The salmon were followed from seawater introduction, starting in Ap ril 1994, until the last: group was slaughtered in February 1996. The findi ngs indicated that the egg and smelt stages were important factors in the p revalence of skin lesions at slaughter. There appeared to be differences in the risk for skin lesions between salmon from different egg suppliers to t he smolt farms. An increase of 3 months between vaccination and seawater in troduction increased the relative risk (RR) for skin lesions (RR = 1.3). Sa lmon vaccinated with a vaccine with adjuvants derived from plant oil appear ed to be at higher risk for skin lesions (RR = 4.6) than those vaccinated w ith a vaccine with adjuvants derived from mineral oil (RR = 1.4). The large r the salmon (from 3.1 to 5.7 kg), the lower the risk for skin lesions (RR = 0.4).