IMMUNE AND ENDOCRINE RESPONSES OF ADULT CHINOOK SALMON DURING FRESH-WATER IMMIGRATION AND SEXUAL-MATURATION

The immune-endocrine responses in spring chinook salmon (Oncorhynchus tshawytscha) were examined during their freshwater migration and final maturation. In 1990, migrating fish had high plasma cortisol titres ( means 200 ng ml(-1)) and generated relatively few antibody-producing c ells (APC) from peripheral blood leukocytes (PBL) (100-200 per culture ). After three weeks acclimation in constant environmental conditions, plasma cortisol was reduced and APC increased. There were no changes in number or affinity of glucocorticoid receptors. Concentrations of s everal sex steroids correlated with APC in females, but there were no such correlations in males. In 1993, fish in a hatchery had significan tly greater cortisol concentrations in primary circulation than in sec ondary circulation, but sex steroid concentrations did not differ betw een circulations. Mean lysozyme activity in the primary and secondary circulation did not differ in June. In August, activity in the primary circulation was significantly less than that of the secondary, perhap s the result of acute stress associated with sampling. While some sex steroids correlated with lysozyme activity, the fact that in both year s all endocrine and immune variables that correlated with each other a lso correlated with the date of sample, raises the question as to whet her or not these are cause-and-effect relations. (C) 1996 Academic Pre ss Limited