Plasma cortisol and 17β-estradiol levels in roach exposed to acute and chronic stress

Plasma cortisol levels were measured as an indicator of physiological stress in roach subjected to brief handling, or to a 14 day period of confinement, and in undisturbed control fish, during winter (water temperature 5oC) and summer (16oC), at which time plasma 17β-estradiol levels were also determined. Cortisol levels in undisturbed roach were low (mean 8.1 ng ml-1 at 5oC; 1.4 ng ml-1 at 16oC) and both handling and handling + confinement significantly elevated blood cortisol levels to 400 and 140 ng ml-1 respectively (at 5oC) and 700 and 600 ng ml-1 respectively (at 16oC). Blood cortisol levels had almost returned to baseline within 4 hours following handling alone but in fish subjected to handling and prolonged confinement cortisol levels remained elevated for up to 168 hours. Differences in baseline and post-stress levels of cortisol, and in the rate of recovery from acute stress, were observed at the two different temperatures and the possible factors underlying these differences are discussed. Circulating levels of 17β-estradiol were significantly reduced within 24 hours of exposure to either acute handling or chronic confinement indicating that the reproductive endocrine system in roach is sensitive to disruption by stressors.