Effects of gill and muscle biopsies on the short‐term behaviour, exercise performance and survival of juvenile lake trout ( <i>Salvelinus namaycush</i> )

Non-lethal biopsy is a valuable tool for gaining insight into the physiological status of fish in the wild and for predicting their subsequent behaviour and survival. However, linking the insights from biopsy to post-release behaviour relies on the assumption that the biopsy itself has no meaningful impact on post-release behaviour or survival (e.g. in animals tagged with electronic devices). This assumption is likely to be questioned by fishery managers, animal ethics committees, and other researchers. To date, there has been very little work to assess the sublethal (or lethal) effects of biopsies on fish, and no such studies have evaluated fine-scale behaviours. Here, muscle and gill tissue samples were taken (both individually and as a combined treatment) from hatchery-reared juvenile lake trout (Salvelinus namaycush) in captivity. Twenty-four hours after sampling, we used two behavioural assays (behaviour within a Z maze and flight initiation distance) and quantified exhaustive exercise performance to determine whether biopsies impacted behaviour or physiology when compared to non-sampled controls. We found no evidence that biopsies had any influence on exploratory and shelter-seeking behaviour in the maze, flight initiation distance, or time to exhaustion (as a proxy for swimming performance). Mortality during a 7-day monitoring period was very low (2% across treatments) and limited to fish that received either a gill biopsy or the combined biopsy treatment. This study provides empirical support for the use of non-lethal biopsy in juvenile salmonids as a means of collecting physiological data on individuals in behavioural studies and experiments.