Abstract
In the harbour of La Spezia (Italy) six polychaete species belonging to the family Dorvilleidae are present. The population dynamics of Dinophilus gyrociliatus , Ophryotrocha hartmanni , O. japonica , O. labronica , O. puerilis and Schistomeringos rudolphii has been studied from August 2002 to August 2003. The density of each species was considerably different and during the year there was a species succession that alternated in dominating the community. The role of the life‐history characteristics of each species and environmental conditions in determining the population dynamics are discussed.