The effect of the parasitic copepod, Mytilicola intestinalis (Steuer) upon the condition of mussels

Abstract

1. Mytilicola intestindlis (Steuer) was found in 100% of mussels examined from Blyth, Northumberland. These mussels varied in length between 3·5 and 7·5 cm.2. The degree of infestation varied from two to fifty-nine parasites per mussel.3. There was an inverse relationship between the condition of mussels of the size group 5·5–5·9 cm. and both the mean number of parasites per mussel and the mean number of parasites over 1·5 mm. in length per mussel.4. The mean weight of flesh per mussel in the size group 5·5–5·9 cm. (shell length) was 3·206 g. from Blyth (parasitized) and 5·975 g. from Conway (not parasitized).5. It is concluded that the presence of Mytilicola is associated with a serious reduction of condition in infested mussels.