Study area
The study area is concentrated in northern Fennoscandia, with lakes
situated in Norway, Finland and Russia. All lakes are located north of
the Arctic Circle, towards the northern end of the distribution of
cool-water fish species (> 68˚N) (See Supplementary
information, Fig. S3, for map of the study lakes and area). To assess
the relative importance of Eurasian perch, we compiled data from 11
lakes sampled on multiple occasions over the last 30 years. The eleven
study lakes were sampled between 2 and 26 times, with time series
ranging from 8 to 32 years (Appendix Table S1).