Pinctada albina is a small, tropical pearl oyster which has established a geographically isolated population in South Australia, well outside its native range in northern Australia. Probably arriving in the 1980s, P. albina has become abundant in the upper Spencer Gulf, causing local concern about potential impacts on native habitat-forming bivalves (Pinna bicolor) through smothering and/or competition. My research is assessing how abundant P. albina has become in South Australia, whether/how fast it is spreading, and what effects it has on the ecosystem (and habitat-forming bivalves). So far, surveys have found P. albina predominantly intertidally (up to 50 oysters m-2 on some sand cays) across the top ~60 km of the Spencer Gulf, suggesting a slow southern expansion since baseline surveys in 2010. The upper Spencer Gulf has low circulation/high water residence times, which may have curtailed spread via planktonic dispersal thus far, but recent records ~120 km further south indicate some individuals now getting into areas where conditions are less hypersaline and thermally extreme, potentially better habitat than the upper gulf. Given further spread is likely, research on how P. albina impacts the ecosystem in the Spencer Gulf is important to understand the eventual threat the species might pose.