Effect of decreased oxygen content on eels (Anguilla anguilla) infected by Anguillicola crassus (Nematoda: Dracunculoidea).

The survival chances of eels with Anguillicola crassus infection of varying intensity and with varying pathological changes were studied in an experimental system devoid of fresh oxygen supply. Eels most severely affected by anguillicolosis died first, while those with less expressed pathological lesions tolerated sublethal oxygen levels for a longer time. Findings were similar at 20-21 degrees C and at 27-28 degrees C; at 27-28 degrees C, however, the fish required a higher oxygen content to survive. The experiments demonstrate that Anguillicola infections substantially impair the eels' natural resistance and, under unfavourable environmental conditions, may lead to their death.