Hematocrits and hemoglobins.Values below or above normal ranges usually indicate anemia or dehydration,which can reflect nutritional disease or physiological changes. 2.Fish health The incidence of diseases during freshwater rearing,as reported in hatchery records describing the treatment of fish were examined. The extent of latent bacterial kidney disease (BKD)as determined by indirect fluorescent antibody technique and the presence (or absence)of certain pathogenic viruses were of particular interest. A histological determination of significant lesions or abnormalities in tissue from the gill,eye,liver,kidney,thyroid,brain,and olfactory sac was undertaken. 3.Survival in seawater net-pens Periodic assessments of survival and growth were made,and the major causes of mortality were determined. These surveys were conducted to provide a documentation of the health and physiological (smolt)condition of the populations of fish involved in the tests,especially at the time of imprinting and release.When the marked adult fish return,the data analyzed from the health and physiology surveys should provide us with information that would indicate any adverse influence on survival.Low survival in the marine net-pens caused by poor health or a low percentage of fish transformed through the smolting stages could bias any attempts to relate returns to imprinting. METHODS AND MATERIALS Hatchery Sampling The sampling of fish from the hatchery stocks for health profiles was based on a combination of statistics and economics.Random sampling from 3 Hematocrits and hemoglobins. Values below or above normal ranges usually indicate anemia or dehydration, which can reflect nutritional disease or physiological changes. 2. Fish health The incidence of diseases during freshwater rearing, as reported in hatchery records describing the treatment of fish were examined. The extent of latent bacterial kidney disease (BKD) as determined by indirect fluorescent antibody technique and the presence (or absence) of certain pathogenic viruses were of particular interest. A histological determination of significant lesions or abnormalities in tissue from the gill, eye, liver, kidney, thyroid, brain, and olfactory sac was undertaken. 3. Survival in seawater net-pens Periodic assessments of survival and growth were made, and the major causes of mortality were determined. These surveys were conducted to provide a documentation of the health and physiological (smolt) condition of the populations of fish involved in the tests, especially at the time of imprinting and release. When the marked adult fish return, the data analyzed from the health and physiology surveys should provide us with information that would indicate any adverse influence on survival. Low survival in the marine net-pens caused by poor health or a low percentage of fish transformed through the smolting stages could bias any attempts to relate returns to imprinting. METHODS AND MATERIALS Hatchery Sampling The sampling of fish from the hatchery stocks for health profiles was based on a combination of statistics and economics. Random sampling from 3