Molecular identification of intertidal rock oyster species in North-Eastern Australia reveals new candidates for aquaculture

Oyster aquaculture in Australia is currently centred on two species, Saccostrea glomerata (Gould, 1850) and Magallana gigas (Thunberg, 1793) which are both susceptible to disease. Disease outbreaks have caused significant losses to the industry and there is currently an appetite for diversification to mitigate risk. Development of other, native oyster species for aquaculture is limited by a poor understanding of their biodiversity and distribution, which is primarily due to the difficulty in distinguishing species based on morphology alone. In this study we sampled intertidal rock oysters from 19 localities in north-eastern Australia and performed phylogenetic analyses based on partial COI and 16S mitochondrial markers. A total of 14 distinct oyster lineages (most likely representing distinct species) were identified from the 357 specimens collected and sequenced. In total, we report the presence of 8 Saccostrea lineages, 4 Ostreinae lineages, one Magallana lineage (Magallana bilineata (Röding, 1798)a recent introduction), and one Talonostrea lineage (likely undescribed). A number of these lineages have broad distributions and attain large sizes, and several are currently cultured in other parts of the world. Although morphological identification is challenging we argue that the large size of the tropical black-lip oyster, Saccostrea lineage J, enables it to be definitively identified as Saccostrea spathulata (Lamarck 1819), thus providing taxonomic certainty for this commercially important species. The identification of these oyster lineages and their distributions is a fundamental step towards development of viable alternatives for oyster aquaculture in the region.