Perna perna is one of six species on the Australian Priority Marine Pest List (DAWE, 2020) that currently do not occur in Australia. It was also on previous national lists (NIMPCG, 2009a, 2009b) and various state and territory lists.

Occasionally detected in Australian vessel arrival inspections and removed.

The brown mussel, Perna perna, is widespread and abundant in the Western Indian Ocean and the east coast of Africa. It is not present in Australia, but is occasionally detected during on arrival vessel inspections and removed. The species is common along the east coast of Africa up to Mozambique, but is more widely distributed on the west coast (Lourenço, 2012). It is most likely to be introduced to Australia by vessels, so it would be found in or near ports on hard surfaces such as rocky shores, wood, jetties and port facilities. The wide temperature tolerance of P. perna suggests it could survive in the northern half of Australia. It can develop dense populations, clogging pipes and fouling other industrial infrastructure. The species is capable of establishing populations on soft substrates where one or a few mussels attaches to a small hard surface, such as a shell or rock, then other mussels settle on the first mussels and a colony is built.

The genus Perna is characterised by the anterior position of the pedal retractor mussel, posterior retractor muscles that are widely separated, and the absence of any anterior adductor muscle (Hicks and Tunnell (1993). The brown mussel, P. perna, is large, typically reaching 90 mm, but has been recorded up to 170 mm in shell length (Vakily, 1989). It has a smooth shell with concentric growth lines, a purple nacreous interior and a straight ventral margin with 10 to 18 primary lateral teeth (Siddall, 1980). The outside periostracum is dark brown with yellow-green near the ventral margin (Hicks and Tunnell, 1993). The main characteristic distinguishing P. perna is the presence of enlarged sensory papillae along the mantle margins (Siddall, 1980). Perna perna is closely related to the Asian green mussel, P. viridis, and the New Zealand mussel, P. canaliculus, both of which have green shells, particularly in young individuals. It can be easily separated from the common mussels (Mytilus spp.) which are blue-black in colour.