Abstract
Two new records of Mytilidae, Aulacomya ater ater (Iredale, 1915) and Mytilus cf. galloprovincialis (Lamarck, 1819), are reported for Macquarie Island. The former is considered to have been a recent arrival at the island, but is apparently not yet established there, which raises issues of management response and the need for a species inventory update to enable appropriate management of alien species in the future. The mode of arrival of Mytilus is uncertain but it is possibly indicative of an already established, but previously unreported, population.