Sturgeons are a species of fish that historically frequently found their way into Slovenian watercourses. The current state of sturgeon populations in Slovenia remains unknown, as there are no studies regarding their occurrence and abundance. The aims of this thesis are to determine, in which areas were sturgeon finds most frequent in the past, which method of sampling is most appropriate for smaller rivers on a European scale, such as the Mura and Sava and to confirm or deny their presence. We determined potential sturgeon feeding habitats, catalogued abiotic factors, took a sample of macroinvertebrates and then sampled sturgeons with the drift net method and demersal longlines. We also obtained data on electrofishing for comparison. Furthermore, we used sonar to determine potential wintering habitats, which we sampled with trammel nets. The latter method yielded the highest diversity of sampled fish, but we failed to confirm the presence of sturgeon with any of the methods employed. The reason for our findings could lie in the relatively low fishing effort and short duration of sampling. It is possible that due to riverbed regulations Slovenian watercourses no longer possess habitats appropriate for sturgeon habitation. Furthermore, past fishing pressures and migration barriers downstream on the Danube could have reduced population sizes to such an extent, that they have not been able to reclaim their historic habitats yet. Future studies of sturgeon occurrence in Slovenia should focus on supplemental stocking of sturgeon and monitoring of stocked individuals using telemetry or the use of eDNA.
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