The incidence and effects of Mytilicola intestinalis in Mytilus edulis from the Rías of Galicia,North West Spain

The parasite Mytilicola intestinalis, found in Mytilus edulis, has been studied in the Rías de Galicia, an area of intensive raft cultivation of mussels. Levels of infection have increased since the only previous survey, but a significant effect on condition index was found in only a few samples, and only on one occasion in cultivated mussels. Reproduction of the parasite was continuous throughout the year, but with a slight increase in numbers of embryo-bearing females in the spring and summer. Infestation increased with host size and with the depth from the surface on cultivation ropes.