Plasma corticosteroid and chloride dynamics in rainbow trout, Atlantic salmon, and lake trout during and after stress

Levels of plasma corticosteroids and chloride were studied in rainbow trout (Salmo gairdneri), lake trout (Salvelinus namaycush), and Atlantic salmon (Salmo salar) after 6 h of confinement in a shallow dipnet. Plasma corticosteroids increased more sharply in rainbow trout than in the other species during the confinement, and returned to resting levels more slowly. Plasma chloride levels decreased significantly from resting levels in both rainbow trout and Atlantic salmon confined for 6 h and had not recovered 12 h after release from the dipnet; very little effect was observed in lake trout. Both plasma corticosteroid and chloride dynamics appear to vary widely in closely related species. The differences do not appear to be related to ease of maintaining the species in captivity.