Before the settlement of the City of Adelaide in 1836, the Port River and Barker Inlet estuary was home to numerous shellfish reefs. The native flat oyster, Ostrea angasi, was plentiful in the area at that time but is unfortunately now only found occasionally. This is in part due to overexploitation by dredge fishing from the 1800s to the early 1900s.
Shellfish reefs are living ecosystems made up of many different species and create complex vertical structures which make ideal homes, breeding locations, and food sources for a vast array of native fish and invertebrate. It has been shown that every hectare of living shellfish reef produces an additional 2.5 tonnes of harvestable fish each year.
Shellfish are also efficient filter feeders and can filter and improve water quality, as well as sequestering nutrients and helping to promote seagrass growth.
OzFish volunteers and members of the local community set out to take steps to begin the return of thriving shellfish reefs to the Port River estuary. This built on previous successful trials by the Estuary Care Foundation to return native flat oysters to the waterway.
The volunteers obtained more than 1.1 tonnes of oyster shell from SA Growers before processing them at Fort Glanville Conservation Park. This involved sterilising the shells to ensure they wouldn’t introduce pollutants when reintroduced to the waterway.
The shells were then placed, by hand, into 70 Robust Oyster Baskets (ROBs) which the volunteers also built. These structures are pyramid shaped and made of wire mesh, that safely breaks down in the water, and full of recycled shell.
Adult native oysters grown by the Estuary Care Foundation have also been deployed on the reef which will provide a suitable substrate for the native oyster spat to colonise.
The sites will be monitored by students from the University of Adelaide to determine colonisation by native oysters and other organisms as well as native fish species visiting the site.
Research underpins and informs everything we do – it is part of our OzFish DNA. The pioneering shellfish restoration project in the Port River in Adelaide is no exception. This week, students from the University of Adelaide’s School of Biological Sciences conducted the first monitoring activities on the Robust Oyster baskets (ROB’s) that were installed in the Port River, South Australia, in December last year (2022).
Our members, supporters, and the local community are determined to help restore thriving shellfish reefs to the Port River estuary. There have been previous successful trials by the Estuary Care Foundation (ECF) to return native flat oysters to the waterway. To build on those existing efforts, our Adelaide Chapter worked with the ECF to identify how our ROBs, deployed extensively elsewhere in Australia, could play a key role in returning vitally important shellfish reefs to the Port River estuary.
