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

Abstract

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.

Anaesthesia and handling stress effects on pigmentation and monoamines in Arctic charr

“…Further this trend was to some extent evident in spots on the left side on day 9 but not on day 8. This is in line with the report that anaesthesia induced carotenoid spots in Arctic charr (Backström et al 2015b), as well as the reported stress-inducing effect of the anaesthetic MS-222 in teleost fish (Zahl et al 2010;Readman et al 2013). Thus the anaesthetic treatment before photographing could arguably be the more stressful handling.…”

“…Immediately after photographing, fish were anaesthetized with Tricaine methane sulfonate (MS-222, 0.15 g/L), weighed and measured. The fish were not anaesthetized prior to photographing based upon the apparent spot inducing effects by anaesthetics in Arctic charr (Backström et al 2015b). Isolation of individual fish was created by separating experimental aquaria (170 L, 95 x 41 x 44 cm) into four equally-sized 42.5 L compartments using removable dark PVC walls.…”

“…Earlier results show that anaesthesia increases number of spots (Backström et al 2015b), and therefore this procedure was aimed at deducing if this effect was sustained over time and/or exacerbated by repeated treatment. MS-222 was used as anaesthetic because it is one of two anaesthetics allowed in the European Union (EEC Council regulation 2377/90) and is the one used in the Swedish Arctic charr aquaculture.…”

“…The behaviour during the anaesthetisation process was recorded via a camcorder for further analysis [see below and Backström et al (2015b)]. Fish were kept in the solution until they lost equilibrium and had no response to tactile stimuli.…”

“…Such an assessment could be made during other, routine evaluation of brood stock, such as weighing and measuring. These procedures, however, usually involve anaesthetics; however, anaesthetics may increase the number of carotenoid spots (Backström et al 2015b). There is also an association between pigmentation and monoaminergic activity (Backström et al 2015c).…”