Assessing natural oyster resources in the Noosa River to restore a functional estuary.
Shellfish reefs are culturally, economically, and ecologically important but have almost entirely disappeared from Australia’s coastlines. In the Noosa River estuary, oysters were once abundant but have not recovered since over-harvesting in the late 19th century. The Noosa estuary appears to be a melting pot for both warm and cool climate species, and although a variety of oysters have been recorded, DNA evidence is required for confident identification. Due to differences in the biology and habitat preferences of oyster species some are likely to be more suitable for shellfish reef restoration projects than others, but this knowledge of which oyster to use and when is limited for places like Noosa.
In this project, Griffith University used traditional collection methods as well as CSI-like environmental DNA technology to test the diversity of species present, building on the existing knowledgebase developed through NBRF and its research partners in existing projects. Although the new methods used enables detection of oyster species that are rare or that live in areas that are difficult to access; no evidence was found of the occurrence of the elusive “Noosa Mud Oyster” or if it was a separate species from the rock oysters.
This project also evaluated which surfaces are best for a range of oyster species to settle on. To do this, a few different types of settlement plates and dead oyster shell were deployed over the 2019 Summer to catch baby oysters. Despite the dry conditions, quite a few oysters were caught around the estuary and genetic analyses was able to determine their identity. This critical genetic information will be used to provide a key for future monitoring and for the assessment of oyster diversity throughout the Noosa estuary.
This project aimed to:
- Evaluate the distribution and diversity of oyster species within the Noosa River estuary.
- Evaluate oyster settlement preferences.
- Investigate environmental DNA techniques for detection and monitoring of restored reefs. This will directly inform the design of reef modules to maximise settlement of oyster species for ongoing restoration projects.
This critical genetic information will be used to provide a key for future monitoring and assessment of oyster diversity throughout the Noosa estuary. The results of this research will inform ongoing restoration projects, including Noosa Council’s oyster restoration program with The Nature Conservancy. The project was led by Dr Carmel McDougall (Griffith University), and supported by Dr Simon Walker (Ecological Service Professionals).
This study identified key shellfish species and documented genetic determination of oyster biodiversity in the Noosa River. The findings are expected to lead to improved design and efficiency and efficacy of current and future restoration efforts aimed at reviving these lost or threatened ecosystems.
The study found that:
- Minimally, there are four species of rock oyster present in the estuary. These include Saccostrea glomerata (the Sydney rock oyster), Saccostrea lineage B, Saccostrea lineage G, and Ostrea equestris.
- The oysters (and their spat) cannot be reliably identified by morphology alone.
- Only eDNA techniques were able to identify all four oyster species.
- Oyster diversity appears to be higher near the river mouth than in the upper reaches, with Saccostrea glomerata the sole species present upstream (Lake Cooroibah mouth).
- Several other native shellfish were identified in the estuary, including pearl oysters (Pinctada albina/nigra species complex), hairy mussel (Trichomya hirsuta) and leaf oyster (Isognomon ephippium, identified by morphology only).
- eDNA has been established as a useful technique for the initial detection of species within an estuary, however other methods are preferred for fine scale distribution assessments.
This project was completed in May 2021.
Ecological Service Professionals (ESP)