Social housing aids recovery from stressors in zebrafish

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. 

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.