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 30min 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.