Effect of an acute necrotic bacterial gill infection and feed deprivation on the metabolic rate of Atlantic salmon Salmo salar

In this study, experiments were conducted to examine the effect of an acute necrotic bacterial gill infection on the metabolic rate (M O2) of Atlantic salmon Salmo salar. Fed and unfed Atlantic salmon smolts were exposed to a high concentration (5 × 10 12 CFU ml -1) of the bacteria Tenacibaculum maritimum, their routine and maximum metabolic rates (M O2rout, and M O2max, respectively) were measured, and relative metabolic scope determined. A significant decrease in metabolic scope was found for both fed and unfed infected groups. Fed infected fish had a mean ± standard error of the mean (SEM) decrease of 2.21 ± 0.97 μM O 2 g -1 h -1, whilst unfed fish a mean ± SEM decrease of 3.16 ± 1.29 μM O 2 g -1 h -1. The decrease in metabolic scope was a result of significantly increased M O2rout of both fed and unfed infected salmon. Fed infected fish had a mean ± SEM increase in M O2rout of 1.86 ± 0.66 μM O 2 g -1 h -1, whilst unfed infected fish had a mean ± SEM increase of 2.16 ± 0.72 μM O 2 g -1 h -1. Interestingly, all groups maintained M O2max regardless of infection status. Increases in M O2rout corresponded to a significant increase in blood plasma osmolality. A decrease in metabolic scope has implications for how individuals allocate energy; fish with smaller metabolic scope will have less energy to allocate to functions such as growth, reproduction and immune response, which may adversely affect the efficiency of fish growth. © Inter-Research 2007.