The effect of anesthetics on carotenoid pigmentation and behavior in Arctic charr (Salvelinus alpinus)

Status of individual animals is often shown in pigmentation. For instance, stress responsiveness is associated with melanin-based pigmentation in vertebrates in general. This pattern is evident in Atlantic salmon (Salmo salar) and rainbow trout (Onchorhynchus mykiss) with melanin-based spots indicating stress coping style. Arctic charr (Salvelinus alpinus) differ from other salmonids in pigmentation but have an association between carotenoid-based pigmentation and stress coping style. These pigmentation differences could be used as a fast and simple tool for improving breeding programs. However, the procedure for photographing individuals is stressful. Therefore we wanted to investigate if three common inhalation anesthetics could be used to reduce the stress involved in the procedure compared to a no-anesthetics group. Behavior was also monitored during the anaesthetization. All three anesthetics (AquaCalm, Benzocaine, and MS-222) differed in pigmentation compared to the no-anesthetics group, by having a higher number of spots. In the anesthetic treatments as well as the no-anesthetics group the fish had elevated plasma cortisol levels. In fact the no-anesthetics group had higher cortisol than treated fish. This was probably procedural differences such as time affecting the stress response. Further, in a longterm experiment all fish survived and had similar condition factors one week after photographing as before. Therefore the method for photographing Arctic charr is deemed safe and could be used for as a tool for estimating stress coping style, but careful planning is needed for experiments using it.