Anguillicolosis of the European eel (Anguilla anguilla) in he Czech Republic

The nematode Anguillicola crassus, a specific parasite in the swimbladder o f eels, was found in the Czech Republic, for the first time, in the Elbe Ri ver near Hrensko in 1991. This parasite was brought into streams and variou s reservoirs of the Czech Republic with stocks of elvers probably in 1990-1 992. In the present review, data on systematics, morphology and various bio logical aspects of this parasite, and on the significance of paratenic para sitism in its life cycle are presented and discussed. In 1993-1996, A. cras sus was recorded at five and twelve localities in the Elbe River basin and the Morava River basin, respectively, with relatively high values of infect ion prevalence and intensity. The effects of the parasite on the host are a nalysed and discussed as regards the values of the length-weight relationsh ip and of amino acid concentrations in the muscles of infected and uninfect ed eels. The infection and mortality parameters depend on the fish total le ngth. The eels infected by A. crassus show abnormal behaviour before their death. Pathological changes in the swimbladder and adjacent tissues are ver y distinct in infected eels. The factors producing eel mass mortality due t o anguillicolosis are assessed in detail from the results of investigations performed in the Vranov dam lake (South Moravia). In this reservoir, the w eight estimation of eels killed by anguillicolosis in 1994 was more than 3. 5 t. The data on effects of eel mass mortality on the eel lower yields by s port anglers during subsequent years are included.