Time course of osmoregulatory, metabolic, and endocrine stress responses of Pacific halibut following a 30-min air exposure

Endocrine, metabolic and osmoregulatory changes in Pacific halibut upon capture and at intervals following a 30‐min air exposure were measured. Concentrations of cortisol, sodium, and chloride in plasma and serum peaked two hours after the stressor. Thirty minutes after a 30‐min air exposure concentrations of glucose in plasma had increased significantly from levels obtained immediately after the stressor and remained elevated for up to 4 h. Plasma lactate was also elevated 30 min after the stress treatment and lactate concentrations increased significantly at each subsequent sampling interval, 2 and 4 h. There was a significant linear increase in plasma lactate for fish sampled from 1.5 to 6.5 h after capture. Incidence of delayed mortality was low; of 22 experimentally stressed animals only one died over a 10‐day monitoring period. These data illustrate the difficulties in using single time‐point plasma indices of stress to assess condition of animals after capture since the time‐course of physiological changes associated with the stress response vary with parameter measured and may take hours to be fully expressed.