BioProject

Aquaculture conditions favourite exposure of farmed fish to stressful factors leading to negative impacts on welfare and performance. More...

Aquaculture conditions favourite exposure of farmed fish to stressful factors leading to negative impacts on welfare and performance. Among many factors, water quality is considered as one of the primary stressors in fish which affect growth and reduce feed intake. The present study aims to assess in rainbow trout the effect of a chronic exposure during 21 days to deteriorated water quality obtained by reduction of the water flow in the tank. Such protocol mainly led to a reduction in O2 levels (30-40% oxygen saturation) and a two fold increase in NH4-N and CO2 levels to non-stressful values. Thus, we questioned whether such chronic conditions which modified growth performances also affected basal and acute stress plasma cortisol levels and induced a deregulation of HPI (Hypothalamo-Pituitary-Interrenal) axis responsiveness. After 2 and 10 days exposure, no significant effect on basal and acute stress plasma cortisol levels was observed. Moreover, these treatments had very minor effects on expression of the HPI axis genes involved in regulation of cortisol secretion. However, after 21 days exposure, a significant increase in cortisol levels after an acute stress was observed. The most significant differences in gene expressions were also observed at the level of the head-kidney with genes involved in cortisol production and its regulation. These HPI axis responses are clearly different from those previously reported for other allostatic load experiences. Overall, the present study illustrates the pleiotropy of the HPI-axis response during allostatic load conditions, and the importance to consider not only the nature of the stressor but also its duration and intensity. Overall design: During the 3-week experiment (deteriorated water quality stress), the photoperiod was maintained at 12:12 (Light: Dark) and the mean water temperature increased from 10.5 to 12.25°C. The fish were fed ad libitum 3 times per day. Total RNA from pituitary gland and head kidney was profilied. Less...