Migratory ability of Orconectes limosus through a fishpass and notes on its occurrence in the Czech Republic

The occurrence of the spiny-cheek crayfish in the Czech Republic was first reported in the 1980's in the Elbe River and is a result of its upstream migration from Germany. This study confirms that this species occurs in many other localities across the Czech Republic. Its migration ability was experimentally studied at a thirty-chambers fishpass located at a hydroelectric power station in the Elbe River. Group-marked crayfish were placed into 3 selected chambers. Their up- and downstream movement was then registered for 30 min after crayfish stocking. We found that a large portion of the experimental crayfish was passively carried along the stream and was caught in the lowest chamber. The movement of crayfish against the water current towards the higher-positioned chambers was not recorded. However, crayfish showed to have a high ability to hold their position in a strong water flow. Overall, 56.7 +/- 9.43%, 6.7 +/- 9.43% and 3.3 +/- 4.71% of crayfish remained in the chamber of insertion and 23.3 +/- 4.71%, 30.0 +/- 14.14% and 26.7 +/- 17.00% of crayfish migrated to the lower-positioned chambers.