Shellfish restoration underway on the Port River, South Australia
Our Adelaide Chapter is helping to restore the functionally extinct native flat oysters (Ostrea angasi) in the Port River Estuary, South Australia.
Across three working bees, 28 rec fisher volunteers constructed 70 Robust Oyster Buckets (ROBs) and filled them with more than 1.1 tonnes of recycled oyster shell. They then helped to deploy them at strategic locations in the Port River estuary, dedicating more than 188 hours so far to delivering the project.
The decline of shellfish reefs in South Australia
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.
Working together to provide a restoration solution
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.
They obtained more than 1.1 tonnes of oyster shell from SA Growers before processing them at Fort Glanville Conservation Park. First, they sterilised the shells to ensure they wouldn’t introduce pollutants to the waterway.
By hand, they then built and filled 70 ROBs with the shells. Pyramid shaped and made of wire mesh, that safely breaks down in the water, the ROBs are a proven method for promoting shellfish growth.
Now that the ROBs have been deployed in locations identified by marine scientists to offer the best chance for oyster growth, they will be monitored by students from the University of Adelaide.
This will let us know how successful the ROBs have been in encouraging colonisation by native oysters and other organisms, and the benefits this will have for native fish species visiting the site.
If you want to find out more about this and other shellfish reef restoration activities we’re delivering across Australia, please visit the Shellfish Restoration project page.
We’d love you to get involved in supporting our goal to deliver better habitat for better fishing.
This project is supported by BCF – Boating, Fishing Camping, The Estuary Care Foundation, Primary Industries and Regions SA (PIRSA), Renewal SA, University of Adelaide, Environment Protection Authority, Government of South Australia – Department of Environment and Water, and Flinders Port Holdings.
