Antarctic fish can survive prolonged exposure to elevated temperatures

The Antarctic notothenioid Pagothenia borchgrevinki was collected from the stenothermal waters of McMurdo Sound in the summers of 2004, 2005 and 2006. Acclimation ability at 4° C was tested in healthy P. borchgrevinki and in individuals infected with x‐cell gill disease. All healthy fish successfully acclimated to 4° C, establishing compensatory changes in resting oxygen consumption rate (R_rest) and critical swimming speed (U_crit) during a 1 month acclimation period, which were maintained during a longer, 6 month acclimation period. In contrast, individuals infected with x‐cell disease were unable to acclimate to 4° C, demonstrating significantly reduced survival rates compared with healthy individuals at 4° C. Measurements of R_rest suggest that limitations in the ability of x‐cell fish to uptake oxygen from the external milieu may have a negative effect on their survival at 4° C.