Prolactin and Growth Hormone Concentrations in the Serum and Pituitary Gland of Adult Migratory Sockeye Salmon (Oncorhynchus nerka)

Abstract

When sockeye salmon entered the Fraser River the prolactin content of the serum and the pituitary gland was reduced by 27 and 36%, respectively. During migration to the spawning grounds the serum concentration increased considerably (81%), while the pituitary concentration was gradually restored to that of the first seawater sample. Serum concentration of growth hormone gradually increased during the migration (29%), while growth hormone in the pituitary glands initially decreased (13%) then increased (12%) as the fish approached the spawning grounds. The changes in prolactin concentrations appear to be related to a change in salinity, whereas growth hormone changes were unaltered at this time.