Histological Comparisons of the Adrenal-Cortical Cells of Hatchery and Wild Landlocked Atlantic Salmon (Salmo salar)

No differences were found in mean diameters of adrenal-cortical cell nuclei between hatchery parr of landlocked Atlantic salmon (Salmo salar) killed immediately after removal from hatchery rearing pools and wild parr electrofished in two streams, and between hatchery and wild parr held for various periods in an outdoor stream aquarium simulating natural conditions. The similarities suggested that the wild and hatchery parr were similar in physiological response to environmental stress. In both hatchery and wild parr, the diameters differed at different times, indicating a downward trend from May to August in the one year of the study. No consistent relation was found between nucleus diameter and social behavior.