Aktivita raka signálního v podmínkách malého toku

The signal crayfish is one of the oldest invasive crayfish species in Europe, causing ecological and often economic damage in newly invaded locations. The invasion and associated problems can be monitored in real-time on the Křesanovský brook, where regular eradication measures have been carried out for six years. However, the detailed and comprehensive impact of these activities on the crayfish population as a whole and any changes in individual behaviour have not yet been studied in detail. To obtain relevant data for this purpose, this thesis video-recorded the situation in the stream in monthly cycles from May to September 2021, with recordings taken the night before and the night after thorough manual crayfish catching in the brook, evaluating the number and activity of observed crayfish. The results did not show that the trapping had changed the overall crayfish activity. Even with a high number of captured crayfish, the weakened crayfish population after trapping showed the same overall activity as the complete population before trapping (presumably due to an increase in individual activity in response to catching and accompanied habitat disturbance). Furthermore, the results underline the previously assumed low success rate of eradication efforts at the site and confirm that barriers in the stream are not sufficient to stop the signal crayfish spread. These findings will help to better understand the impact of eradication measures on signal crayfish populations. As this was the first research of its kind, this thesis opens up opportunities for methodological improvements and further development, as well as posing many new questions that need to be addressed. The ultimate goal of these efforts is to improve management interventions against invasive signal crayfish.