Mytilicola intestinalissteuer and the condition of its hostMytilus edulisL.

The incidence of infestation of Mytilus edulis L. with Mytilicola intestinalis and the condition (meat content) of Mytilus was monitored 1976-1985. For the individual years the number of Mytilicola was positively correlated with meat content of Mytilus while comparison between individual years showed a negative relation between number of Mytilicola and the condition of Mytilus. It is concluded that Mytilicola has a strong adverse effect on the condition of its host, but that this effect is masked in samples with large variation in the condition of Mytilus.