Restoring shellfish ecosystems in the Swan-Canning Estuary
PROJECT UPDATE: The Conservation Action Plan for the Swan-Canning Estuary has been released. READ THE FULL UPDATE >>
The Swan-Canning Estuary lies at the heart of Perth as its two rivers meet and flow onward to the ocean at Fremantle. The Swan River, also known as the Derbarl Yerrigan, it is a place of deep spiritual and mythological significance to south-west Western Australia’s Traditional Owners, the Noongar people. For thousands of years this area has been vitally important as a source of food, water, transport and recreation.
The area is home to diverse wildlife:
- Over 130 species of fish including bull sharks, rays, catfish, herring, pilchard, bream, flatheads, leatherjackets and blowfish.
- Seahorses coexisting with jellyfish, anemones, seagrass, prawns and crabs.
- Resident population of around 20 Indo-Pacific Bottlenose Dolphins.
- More than 80 bird species including the eponymous Black Swan, Silver Gull, Twenty-eight Parrot, Australian Pelican, Forest Red-tailed Black Cockatoo, Australasian Darter and Sacred Kingfisher, as well as many cormorants (locally referred to as 'shags'), herons, egrets, grebes and ducks.
- Small mammals like the Water Rat, Brush-tailed possums and Quenda (or Southern Brown Bandicoot).
Perth's missing link
What’s missing from this rich ecosystem are the abundant shellfish reefs that once covered part of the estuary’s floor. Many people might not know that shellfish reefs were once found in our bays and estuaries from Perth all the way around the southern and eastern coastline to Noosa, Queensland.
Due to over-exploitation they are now found only in a few bays in Tasmania and NSW. The story of shellfish in the Swan-Canning Estuary is rich and complex. Oyster shells come from a thriving population some 10,000 years ago. In the early 1900’s up until the 1970’s, they were systematically dredged to provide the mortar to build Perth and the surrounding areas.
When those ecosystems existed, they filtered water and kept the estuary healthy. After the limestone bar was opened at Fremantle to allow for safe passage and the building of the Port, Blue Mussels took up the mantle as the key species providing this critical service. However, these too have been lost to over-exploitation and water quality issues. With the loss of these natural water filters that historically lived there, the health of the estuary is at risk, but we’re bringing them back thanks to a $2million dollar pledge from Minderoo Foundation, funding from Lotterywest, the WA State Government, the Australian Government and from a range of donors in Western Australia.
In the past year we have received further support and are gearing up for our full-scale reef build.
Benefits of shellfish reefs
There are significantly more residences, businesses, open spaces and clubs that front the Swan-Canning Estuary than there are around Sydney harbour, so we understand how important the estuary is to the people who live there and visit in the area.
Bringing back Australia’s most threatened marine ecosystem – native shellfish reefs – also brings back a wealth of benefits for people and nature. This includes improved local fish populations as reefs act as fish nurseries, better water clarity due to the filtration power of shellfish, increased shoreline protection, extra feeding habitat for threatened migratory shorebirds, and an overall increase in biodiversity. For locals, it will increase opportunities for recreational fishing, economic development and tourism.
“The Swan and Canning rivers need to be kept clean and healthy,” said Nicola Forrest, Director of Minderoo Foundation. “They flow through the heart of our city and reach our precious coastline. These rivers are celebrated for their natural beauty and cultural and recreational significance and should remain accessible for all West Aussies, and our visitors, for decades to come.”
“Perth and Fremantle communities, from the time of European settlement, have greatly enjoyed what the Swan River offered in terms of its resources and beauty but the river is under increasing stress, mostly due to nutrient inflow. We greatly appreciate Minderoo’s and other donors’ generous pledges and I invite other West Australians to give something back to improve their river’s health.” said Rich Gilmore, then-Director of The Nature Conservancy Australia.
Thanks to some of Western Australia’s most respected companies and philanthropists who are also backing the project including Jock Clough, Adrian & Michela Fini, Austral Fisheries, Gavin Bunning, The McCusker Foundation, Major Holdings Pty Ltd, James & Marion Taylor, and Michael & Margrete Chaney.
Boosting native Pygmy Mussel populations
The Nature Conservancy is working with Perth NRM, Murdoch University and OzFish to give the native Black Pygmy Mussel reefs a helping hand. This project aims to assist in the creation of additional habitat at 20 sites in the Swan-Canning.
In the past, this small mussel covered snags and formed large beds within the waterway. It was a key food source for important recreational fish species, like the Black Bream. It also helped to maintain the health of the estuary by filtering water and creating additional habitat for small crustaceans. There is a huge opportunity to increase species population.
This will support recreational fishing activites and support the overall health of the estuary.
The first phase of the project will focus on site selection and method trials to work out the best way to attract and maintain mussels on new habitat. This phase will run until late-2022 and will involve the following:
- Identifying 20 sites for habitat installations
- Trial of 4 methods using biodegradable materials
- Monitoring of fish and mussels at trial sites
- Developing an expansion plan for Phase 2, based on results from Phase 1
For more info, email: firstname.lastname@example.org
“This project is funded by the Fisheries Habitat Restoration Program, supported by Perth NRM through funding from the Australian Government.”