Acute stress response in triploid rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis)

The purpose of this study was to determine whether triploid salmonid fishes differ from diploids in their hematological and physiological responses to an acute handling and confinement stress, induced by netting fish from their tanks and placing them in a bucket. Blood samples were collected from fish prior to the handling stress and at either 30 min (rainbow trout) or 20 and 40 min (brook trout) confinement in the bucket. Plasma cortisol, glucose and chloride levels, hematocrit, hemoglobin concentration, total blood cell concentrations (erythrocytes and leucocytes), and differential leucocyte concentrations and their relative proportions were measured. As expected, resting blood cell concentrations were significantly lower in triploids than in diploids. In all other respects, triploids showed little difference from diploids in either values prior to the stress or in changes in these values induced by the acute stress. Both diploids and triploids showed a marked stress-induced increase in hematocrit and plasma cortisol and glucose, accompanied by a decrease in lymphocyte concentrations. Other values showed minimal or no change resulting from the stress. Triploid salmonid fishes therefore appear to exhibit a typical acute stress response, as has been well described for diploids. (C) 2000 Elsevier Science B.V. All rights reserved.