Investigation of behavioural and physiological responses to fin-clipping in zebra fish

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Zebra fish are extensively used as research animals. Use of zebra fish as experimental animals is increasing, mainly because zebra fish have particular characteristics that make them very suitable for genetic research on embryo development and are becoming popular as a replacement for mammals in biomedical, pharmacological and genetic research. Genetic analysis requires a tissue sample, which in zebra fish is obtained through fin clipping, i.e. the surgical removal of part of the caudal fin. This procedure is carried out under general anaesthesia but without the provision of pain relief following the procedure. Thus, there is potential for fish undergoing this procedure to experience pain once they wake up. Recent studies have provided anatomical, neurophysiological and behavioural evidence for the capability of different species of fish (including zebra fish) to experience pain. Tailfin clipping has been proven to induce pain-associated responses in various fish species. However, the potential of fin clipping to be painful and therefore produce changes in the behaviour and physiology of zebra fish has not been investigated. As large numbers of zebra fish undergo this procedure every year we hope this study will help refine this procedure if required and improve fish welfare in research. By video-recording and analysing the behaviour and measuring physiological parameters (such as operculum/respiratory rate and non-invasive stress hormone -cortisol- measurement) of tailfin-clipped fish and comparing these parameters with appropriate control fish, we would identify potential behavioural and physiological indicators that might reflect a painful response to the injury. We will also develop behavioural tests which would assess if fin clipping evokes an emotional response in zebra fish, manifested as changes in motivation and attention. These tests will measure, for example, the fear response to a novel object and the use of enrichment items such as an opaque cover, both of which have been reported to be decreased in fish suffering from pain.The final part of the study would aim at investigating the effect of painkillers (i.e. morphine) on the behavioural and physiological pain indicators identified in the first part of the study, in order to validate that these indicators are indeed caused by pain. The results from this study could potentially influence future policies for tissue collection for genetic analysis and lead to the development of refinements for this procedure, for example with the use of appropriate pain relief. Pain indicators identified during this study could be used in further studies and could also be integrated into pain assessment protocols, monitoring systems and as parameters for assessing painkiller efficacy. Findings from this study could also be implemented in other potentially painful procedures which would result in improving the welfare of laboratory fish worldwide.