Hydro-Peaking Operations and Black Bass, Do Cortisol Levels Rise with the Flow?

Overall condition of fishes can be influenced by the amount of stress experienced.   Stressors, such as alteration in temperature, oxygen or hydrology, can induce acute or chronic stress.  Cortisol response is a good indicator of acute stress and additional measurements of stress include leukocyte profiles, with neutrophils increasing and lymphocytes decreasing (N:L).  In this study we are investigating whether the Hypothalamus-Pituitary-Interrenal (HPI) axis is affected in Alabama and Redeye Bass due to hydro-peaking operations at Harris Dam on the Tallapoosa River, Alabama.  Fish were collected in fall on the Tallapoosa River and a reference site on Hillabee Creek, which is an unregulated tributary.  Once collected, fish were tagged and plasma samples were collected within five minutes of capture.  Fish were transferred to a 113.5-L tub and remained in the tubs for a 1 h, and another sample collected.  This confinement is expected to trigger the stress response in the HPI axis and cortisol concentrations and N:L should rise.  The blood samples were assayed for plasma cortisol levels and blood smears were created and read.  Preliminary results show that there is a trend for both baseline cortisol levels and N:L to be higher in the fish found at the disturbed location.