A new study has shown that group housed zebrafish show lower levels of stress and anxiety when they undergo stressful or painful procedures like fin clipping than those who are housed singly. The research, funded by an NC3Rs project grant, was recently published in Animal Behaviour.
Increasing numbers of fish are being used in scientific studies, and evidence is growing to show that fish experience stress and respond to pain with mechanisms comparable to mammals. Enriched tanks have been shown to reduce anxiety in fish, and housing in social groups is considered crucial for gregarious fish such as zebrafish (Danio rerio).
Led by Dr Lynne Sneddon from the University of Liverpool, this study compared recovery from common laboratory procedures (anaesthesia and fin clipping) in male zebrafish (AB strain) housed individually, in pairs and in groups of six. The team analysed responses which have been established as valid markers of stress, such as erratic movement, time spent at the bottom of the tank and stress hormone (cortisol) levels.
Anaesthesia alone and anaesthesia with fin clipping both had a significant impact on individually housed zebrafish, with these fish showing increased stress and behavioural alterations. The responses of zebrafish housed in groups was less pronounced, with group housed fish resuming normal behaviour more quickly than individuals or pairs, and showing the lowest cortisol increase.
During the study the researchers, based at the Universities of Liverpool and Chester, also validated the use of water-borne cortisol siphoned from tanks as an accurate and non-invasive measure of physiological stress. This method avoids the need for terminal sampling for measurement of whole body cortisol, helping to reduce the number of fish required for time series studies on physiological stress.
White LJ, Thompson JS, Pounder KC, Coleman RC, Sneddon LU (2017) The impact of social context on behaviour and the recovery from welfare challenges in zebrafish, Danio rerio. Animal Behaviour 132, 189–199; doi.org/10.1016/j.anbehav.2017.08.017