Challenges for fish in warmer waters: the case of the Arctic char

Sigurður Guðjónsson

Institute of Freshwater Fisheries, Iceland

Global warming and climate change will affect the distribution and the abundance of many important fish populations. To assess biodiversity responses to climate change in northern regions, a NordForsk funded research program, NordChar, was initiated and is ongoing on the fish, Arctic char (Salvelinus alpinus). The Arctic char was chosen as a model species due to its wide distribution, which is relatively little influenced by anthropogenic factors, and char is very plastic with both phenotypic and genotypic responses to environmental change. The Arctic char, as other salmonid species, is also an important and highly evaluated fish in the northern regions. In this study, both genetic and biological parameters were investigated to map the species variability. Biological and life history characteristics are extracted from the extensive literature. For the genetic mapping, mitochondrial DNA (mtDNA) was used as it interacts with the energy system of the cell. Genetic characters can therefore be expected to be sensitive to environmental temperature conditions in poikilotherms such as Arctic char.  The genetic work involves two phases. In the first phase, we sequenced the whole mtDNA genome of 128 individuals, chosen to represent geographically and phylogenetically the biodiversity of the species. This robust overview of the genetic variation revealed that some parts of the mtDNA are very variable and in total 468 SNP’s was found. In the second phase, a detailed analysis was done of the phylogenetic and differentiation among populations within and among locations across the species range using selected highly variable areas of the mtDNA.  At the same time this is an explorative genome scan to detect candidate loci for adaptation along then gradient of latitude or environmental temperature. Preliminary results show highly diverged lineages with regional distribution but moderately diverged lineages can be widely distributed geographically.  Furthermore moderately diverged lineages can be sympatric within the same watershed. The findings will be compared to different life history patterns. The study has produced a genetic tool that can be used to monitor adaptive genetic divergence in Arctic char.  Furthermore, the findings will improve understanding on what happens as climate changes both for Arctic char and other fish species.