Validating skin swabbing as a refined technique to collect DNA from small-bodied fish species

DNA samples are often used to identify fish before they are utilised in other experiments. Our recent research has shown that skin swabbing can be used to collect DNA for genotyping, and that swabbing causes less harm to fish than fin clipping, another common technique. In this study we investigated potential refinements to the skin swabbing protocol by pre-treating fish with the analgesic lidocaine. We could not detect any differences in cortisol release, behaviour or expression of stress axis marker genes in skin swabbed sticklebacks or zebrafish regardless of lidocaine application. In contrast, fin clipping caused changes in cortisol release, gene expression and behaviour when analgesia was not used. These changes were rescued by pre-treatment with lidocaine confirming that analgesia was effective. The results demonstrates that skin swabbing is a refined technique for DNA collection that does not require analgesia.