Clarifying the natural distribution of Saccostrea (edible rock oyster) species in Western Australia to guide development of a fledgling aquaculture industry

Rock oysters of the genus Saccostrea currently form the basis of a significant aquaculture industry in Australia, which is poised for expansion regionally, including within Western Australia. To limit the potential negative consequences of aquaculture-related translocations, current policy in Western Australia requires the local sourcing of rock oyster aquaculture broodstock. This policy, by definition, requires the identification of the optimal aquaculture candidate species from those naturally present in each region under consideration for edible oyster production. Given historical taxonomic confusion, and limited biogeographical data about Saccostrea throughout Western Australia, this study sought to provide baseline distributional data of the genus to underpin the potential development of the industry. A total of 498 oyster specimens were collected across the known range of the genus and vouchered at the Western Australian Museum. Sampling was opportunistic in nature but also included areas with potential or established interest in aquaculture development. All specimens were sequenced for a region of the 16S rRNA gene (488 bp), which is a well-established marker for resolving taxonomy of the genus, with a large comparative dataset available. This new dataset resolved five genetic lineages of rock oyster within the region, which were then mapped to assess distributions. These lineages were designated as Saccostrea lineage A, Saccostrea lineage B, Saccostrea lineage J, S. glomerata, and S. scyphophilla (Peron and Lesueur, 1807), following an established nomenclatural scheme in a group with considerable taxonomic flux. This study extended the known distribution of lineages previously reported in Western Australia (Saccostrea lineage A, and S. scyphophilla) in addition to identifying two previously unrecorded lineages (Saccostrea lineage B and Saccostrea lineage J). Understanding the current distribution and nature of rock oyster distributions in Western Australia is fundamental to the development of a sound policy framework, as well as a research and development strategy for a strong and sustainable aquaculture industry.