Project Sulzkarsee Final Report 2023

The chemical-physical analyses show that the lake is stratified over the summer months and that a mixture takes place in autumn. In general, the water temperature in 2023 turned out to be warmer than in the past 20 years, with a maximum measurement of 21 degrees Celsius in summer. Variations in the phytoplankton and zooplankton biomass indicate complex interactions within the lake's food chain. The dominance of certain phytoplankton groups and the low diversity of macrozoobenthos as well as the absence of mountain molluscs in the lake indicate that the feeding pressure has increased significantly since the lake was drained by the again very individual-rich population of lizards. Only through a profound understanding of the underlying processes and interactions can targeted measures be developed to establish the ecological integrity of this ecosystem in the long term. The results of the fishing operations underline that the removal of the lizards will not be possible purely through intensive fishing. At present, attempts are underway in the Pyrenees (Spain) and in the Sierra Nevada (USA) to remove used lizards in mountain lakes also with the help of the piscizide Rotenon. For the time being, this is not an option in Austria. The results of these and similar studies can be observed to potentially find an effective way to restore fish-free status in the lake in the future.