DAO 78:37-44 (2007)  -  DOI: https://doi.org/10.3354/dao01853

ABSTRACT: Our aim was to determine possible metabolic effects amoebic gill disease (AGD) on Atlantic salmon Salmo salar. Standard (R_S) and routine (R_ROU) metabolic rates were evaluated by continually measuring oxygen consumption in 2 independent tanks of fish (18.69 ± 1.01 kg m^–3, mean ± SE). Active metabolic rate (R_ACT) and metabolic scope (R_ACT – R_S) were assessed using a chasing protocol and determined at 3 time periods: (1) pre-infection, (2) 3 d post-infection, and (3) 2 d post-treatment. On Day 3 of the study, the fish were infected with amoebae isolated from the gills of AGD-affected salmon (2300 cells l^–1). No significant elevations in R_ACT or metabolic scope were detected 3 d post-infection and 2 d post-treatment; however, significant elevations in R_S and R_ROU were detected 3 d post-infection and 2 d post-treatment. Assessment of R_ROU data, especially for the light period, also indicated a rise in oxygen consumption rate over the course of the experiment. Treatment of AGD-affected Atlantic salmon with chloramine-T (CL-T) appeared to briefly mitigate the rise in R_S, as there was a 30% drop (though non-significant) in R_S following treatment. Despite this, R_S continued the upward trend 1 d following treatment. These results suggest that over the course of AGD development, R_S in Atlantic salmon increases. Therefore, considering the physical conditions which constrain R_ACT, we expect that metabolic scope would become compromised in fish more heavily affected with AGD. Treatment with CL-T shows promise for mitigating the respiratory effects of AGD and potentially minimising the loss of metabolic scope.

KEY WORDS: Amoebic gill disease · AGD · Oxygen uptake · Metabolic scope · Chloramine-T · Atlantic salmon