Øvre Heimdalsvatn, Radiocaesium (Cs-137) monitored annually in brown trout (Salmo trutta)

"This dataset describes a long time serie for monitoring of radioactive radiocaesium isotope (Cs-137) concentration in the brown trout (Salmo trutta) population in a mountain lake (Øvre Heimdalsvatn) situated on the tree line in the eastern edge of the Jotunheimen Mountains. Ecosystem studies at Øvre Heimdalsvatn started in 1957, while this time series for radioecological monitoring started after the Chernobyl nuclear power plant accident in 1986. The aim of this study was to document the long-term changes in the radioactive isotope Cs-137 in brown trout and to elucidate the factors determining changes in Cs-137 activity concentrations over time. This dataset provides only one time serie from the extensive ecosystem studies (initiated in 1957) at Øvre Heimdalsvatn. The mountain lake is at 1090 meter above sea-level with a surface area of 0.78 square kilometer (km2) (78 hectare). The maximum length is 3 km and the maximum width is 396 m. The largest depth is 13 m and the average depth is 4.7 m. Vegetation near the lake ranges from subalpine birch forest with areas of mountain pasture to high alpine vegetation above 1,600 m a.s.l. Originally brown trout was the sole fish species in the lake, but since 1969 the European minnow (Phoxinus phoxinus) has also been recorded and its numbers have subsequently increased substantially. Brown trout for this study were generally caught by gill netting around the lake."