The spread of the eel swimbladder nematode Anguillicola crassus through the Erne system, Ireland.

The spread of Anguillicola crassus was documented and showed an increase in both prevalence (9.9%) and mean intensity (6.7). Infected eels Anguilla anguilla were recorded 30 km downstream of the first recorded sites of infection. Migrating silver eels from commercial nets near the outlet of the Erne during October-December 1999 were also infected. Continued spread of A. crassus through Ireland's major wild eel fisheries now appears likely.