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.