Crayfish; Orconectes limosus; distribution; Czech Republic; migration; fishpass; scuba diving

The crayfish Orconectes limosus is known in the Czech Republic from 1980´s. Now it is frequent in wider part of the Czech Republic. Its migration capacity was experimentally studied on a thirty-chamber fishpass of a hydropower station on the Elbe River. Crayfish were placed into 3 chosen chambers and registered 30 min or 60 min after stocking. Part of the crayfish (15% and 30%, resp.) was passively carried along the stream and they were caught in the lowest chamber. Most of them (50% and 60%, resp.) showed high ability to keep their position in a strong water flow. Motion against the water flow was not recorded. Higher seasonal activity of crayfish was registered at the end of April. Crayfish in the littoral zone were most active from May to August. Diving observation in the river bed (4.2m) reports crayfish only at banks amongst stones with Dreissena mussels, depths 0.5-1 m.

The crayfish Orconectes limosus is known in the Czech Republic from 1980´s. Now it is frequent in wider part of the Czech Republic. Its migration capacity was experimentally studied on a thirty-chamber fishpass of a hydropower station on the Elbe River. Crayfish were placed into 3 chosen chambers and registered 30 min or 60 min after stocking. Part of the crayfish (15% and 30%, resp.) was passively carried along the stream and they were caught in the lowest chamber. Most of them (50% and 60%, resp.) showed high ability to keep their position in a strong water flow. Motion against the water flow was not recorded. Higher seasonal activity of crayfish was registered at the end of April. Crayfish in the littoral zone were most active from May to August. Diving observation in the river bed (4.2m) reports crayfish only at banks amongst stones with Dreissena mussels, depths 0.5-1 m.