Forsøksdyr: Time limit of high intensity sustained swimming in Atlantic salmon

Godkjenningsdato 30.04.2020

Godkjenningsperiode 30.04.2020-30.07.2020

The purpose of this experiment is to quantify for how long Atlantic salmon (Salmo salar) post smolts are able to swim aerobically at a range of swimming intensities in the upper range of its aerobic capacity.
Aerobic or sustained swimming means that the fish primarily is relying on the thin red layer of swimming muscles. It is therefore not using the white muscles where anaerobic pathways are used to generate energy that leads to an accumulation of lactate that eventually causes fatigue. However, the etiology of fatigue can have two origins: If the work intensity is too high and anaerobic metabolism becomes necessary, the origin is failure to produce sufficient energy within a limited amount of time. On the other hand, if prolonged high-intensity aerobic work below the maximum aerobic capacity goes on for too long, substrate depletion to fuel this work load may lead to fatigue. In humans this is commonly known as “hitting the wall”, for instance during marathon running. In fish, this phenomenon has not yet been properly studied.
For this experiment we will be using a larger custom swim tunnel setup that already has been used for numerous previous studies successfully. Based on these experiences, we are not expecting distress of severe injuries or other serious welfare issues. But, as some fish will experience fatigue, the trials must be considered severe, according to official guidelines.
The results obtained here will increase our knowledge of the fundamental physiology of fish significantly, as the experimental design and underlying questions being addressed are novel. Moreover, the interaction between water speed and time on swimming endurance in Atlantic salmon will fill major knowledge gap for the welfare regulation of aquaculture at sites prone to rougher current conditions. Establishing salmon farm sites in rougher conditions, for instance offshore, is currently a widespread trend in the salmon industry. However, it is paramount to confirm whether farmed fish are able to thrive in these new conditions. Hence, there is also a profound timely societal relevance to this experiment.
We plan to use 90 Atlantic salmon post smolts in this experiment.
Regarding the 3R’s: Replacement is not possible as we are investigating whole-animal performances in response to different environmental conditions. Reduction has been used to minimize experimental animals used while not compromising the statistical robustness of the results. Refinement has been optimized in the experimental protocols by reducing handling time, avoiding multiple stressors simultaneously, and by ensuring that the time fish spend being fatigued is minimal owing to rigorous monitoring.