Plasma cortisol and 17 beta-oestradiol levels in roach exposed to acute and chronic stress

Plasma cortisol levels were measured as an indicator of physiological stres s in roach subjected to brief handling, or to a 14-day period of confinemen t, and in undisturbed control fish, during winter (water temperature 5 degr ees C) and summer (16 degrees C), at which time plasma 17 beta-oestradiol l evels were also determined. Cortisol levels in undisturbed roach were low ( mean 8.1 ng ml(-1) at 5 degrees C; 1.4 ng ml(-1) at 16 degrees C) and both handling and handling+confinement elevated blood cortisol levels significan tly to 400 and 140 ng ml(-1), respectively (at 5 degrees C) and 700 and 600 ng ml(-1) respectively (at 16 degrees C). Blood cortisol levels had almost returned to baseline within 4 h following handling alone but in fish subje cted to handling and prolonged confinement cortisol levels remained elevate d for up to 168 h. Differences in baseline and poststress levels of cortiso l, and in the rate of recovery from acute stress, were observed at the two different temperatures and the possible factors underlying these difference s are discussed. Circulating levels of 17 beta-oestradiol were reduced sign ificantly within 24 h of exposure to either acute handling or chronic confi nement indicating that the reproductive endocrine system in roach is sensit ive to disruption by stressors. (C) 1999 The Fisheries Society of the Briti sh Isles.