Temporal developement of interrenal activation after stress in Atlantic salmon
This study aim as describing the response time and peak response of the interrenal activation, including plasma cortisol levels and activation of several genes in parr, smolts and post-smolts of Atlantic salmon. This will involve a standard stress regime of 60 s air exposure in a dip net and euthanization with an overdose of anesthetics after 5-120 min for all individuals involved.
Descriptions of the temporal development of the stress response have been done for several species including Atlantic salmon, but with low temporal resolution. In the stress trials with salmonids blood and other tissues are often sampled at the same time, usually around 30-60 min post-stress, although different stress measures probably peak at different times post-stress, and the temporal development likely varies with to life stage in addition environmental factor such as temperature. Sampling at the peak response would give higher quality of the data and less variation between studies.
Salmon will be netted out from a larger group and held in air for 60 s before they are transferred in groups of 10 to new tanks for sampling after 5, 10, 20, 30, 45, 60 or 120 min post-stress. 10 fish will be sampled without air exposure in order to estimate baseline levels. With 8 sampling point involving 10 fish each, and 3 different life stages, the total number of fish will be 240.
The 3Rs: Replacement: not possible. Reduction: restricting samples to the first hour post-stress, except for one later (2 h) sample point to evaluate recovery. Ten killed fish per sample point is regarded a minimum as a proportion of the samples often have to be rejected, for instance due to outliers or hemolysis in plasma, leaving a lower number for statistical analysis. Refinement: The fish will be held in their home tank until stressed, and thereafter transferred to similar tanks at the same temperature and left undisturbed until sampled. 1 min air exposure as stressor is chosen to secure a clear stress response but still avoid sever stress that could arise from longer air exposure durations.
Descriptions of the temporal development of the stress response have been done for several species including Atlantic salmon, but with low temporal resolution. In the stress trials with salmonids blood and other tissues are often sampled at the same time, usually around 30-60 min post-stress, although different stress measures probably peak at different times post-stress, and the temporal development likely varies with to life stage in addition environmental factor such as temperature. Sampling at the peak response would give higher quality of the data and less variation between studies.
Salmon will be netted out from a larger group and held in air for 60 s before they are transferred in groups of 10 to new tanks for sampling after 5, 10, 20, 30, 45, 60 or 120 min post-stress. 10 fish will be sampled without air exposure in order to estimate baseline levels. With 8 sampling point involving 10 fish each, and 3 different life stages, the total number of fish will be 240.
The 3Rs: Replacement: not possible. Reduction: restricting samples to the first hour post-stress, except for one later (2 h) sample point to evaluate recovery. Ten killed fish per sample point is regarded a minimum as a proportion of the samples often have to be rejected, for instance due to outliers or hemolysis in plasma, leaving a lower number for statistical analysis. Refinement: The fish will be held in their home tank until stressed, and thereafter transferred to similar tanks at the same temperature and left undisturbed until sampled. 1 min air exposure as stressor is chosen to secure a clear stress response but still avoid sever stress that could arise from longer air exposure durations.