In this study we aimed to assess the relative effects of native Ostrea edulis and non-native Crassostrea gigas and their associated epibiotic biodiversity. We recorded epibiont location on the shell as well as the upper or lower valve. Epibiont species richness was significantly lower on C. gigas. The epibiota communities differed significantly between the two oyster species. The continued spread of C. gigas may potentially impact the epibiont biodiversity associated with oyster species in Strangford Lough. Management strategies should prevent sustained population expansion and associated changes in colonisation habitat.