Population trends of Arctic charr (Salvelinus alpinus) in the UK: assessing the evidence for a widespread decline in response to climate change

The UK lies towards the southernmost distribution limit of the circumpolar Arctic charr (Salvelinus alpinus), and native populations of high national conservation value occur in all four component countries. However, given the temperature requirements of this species and the already relatively mild UK climate, there is strong reason to expect a significant negative impact of climate change on local populations. Data were assembled from repeated Arctic charr population assessments using combinations of hydroacoustics, gill netting, entrapment records and fisheries catches at five Scottish populations, five English populations and one Welsh population. These data were then used to test the hypotheses that there has been a widespread decline of Arctic charr in the UK and that it can be attributed at least in part to climate change. Ten of the 11 studied populations exhibited significant 1990-onwards declines in abundance, while only the most northerly population showed a significant increase. Overall, there was a significant positive relationship between the observed population decline ranking and a vulnerability to climate change ranking based on water body latitude, altitude and mean depth. These observations support the hypothesis that this species has suffered a recent and widespread decline in the UK, and although additional factors are undoubtedly also involved in some specific cases, climate change is a significant factor.