In this project we will analyze WGS data to search for genetic differences between fish from populations in an artificially heated coastal bay (heated for 43 years) and fish from reference populations outside the heated area. Focus species is perch (Perca fluviatilis), and sequence data come both from freshly collected samples and from archived tissue samples spanning back to before the heating started, providing an excellent set-up to analyze the potential for warming to induce genetic differences. All WGS come from individual samples, for which we also have trait data (body size and size of various organs, sex, growth, age, gonadal status), which we in a second step aim to associate to the results of the analyses of the sequence information. The current NAISS-project is intended for finalizing analyses for a scientific article, building on preliminary analyses made within a PhD thesis, and is thus a continuation of previous NAISS projects used for the preliminary analyses.