The life cycle of Anguillicoloides crassus begins when the adult nematode releases thousands of eggs in the eel's swimbladder.

Since the swimbladder is the buoyant organ which allows the eel to swim, a severe parasite infestation can hamper its ability to reach its spawning grounds.

Third, the larvae remain for longer within the host's swimbladder wall whilst developing into the fourth larval stage, as opposed to moving directly through it (as occurs in Pacific eels).

The hosts' swimbladder wall becomes inflamed as cells undergo fibrosis, which can prevent further invasion by A. crassus larvae.

[7] Structural changes include possible alterations in the epithelial cells, hindering processes involved in acidification of the blood and leading to a decline in the rate of gas deposition.

The best documented cases of mass A. anguilla mortalities are from the summer of 1991, in Lake Balaton, Hungary, and the Vranov reservoir in the Czech Republic during 1994.

Parallels between Lake Balaton and another water body, the Neusiedler See in Austria, could counter the extreme effects of A. crassus on eel populations under these conditions.

Research has been carried out to precisely quantify the possible damage a given parasite load could have in the ability of a silver eel to migrate and reproduce.

In an experiment to assess the energetic cost of the migration in general, it was shown that eels with less than 13% fat reserves would not be capable of reaching their spawning ground.