Threats to the survival of the Great Barrier Reef have been well publicised. Lesser known is the state of the shellfish reefs of Victoria and South Australia where up to 99% have been destroyed because of a long history of dredge fishing.
A group of scientists, fishers and conservationists is working to restore one of these ecosystems in Victoria’s Port Phillip Bay using mollusc shells recycled from restaurants.
For two years the Albert Park Yachting and Angling Club and The Nature Conservancy, in collaboration with the Victorian Fisheries Authority, have been collecting oyster, mussel and scallop shells from Geelong restaurant and seafood suppliers.
They have so far collected more than 420 cubic metres of shells which otherwise would have ended up in landfill.
Initially the shells were stockpiled and left to cure for six months of exposure to the sun and wind so that any diseases they might have been carrying were killed off.
In November the group began spreading shells and limestone rubble on the sea floor at two sites to form bases for reefs for Angasi oysters (Ostrea angasi). This month the group will work on building a reef base for blue mussels (Mytilis edulis).
These new reefs are being placed where suitable reef habitats have been depleted.
It is hoped that their establishment during the natural oyster and mussel spawning season will lead to remnant populations colonising these reefs.
However they are not relying solely on natural recruitment. More than 10 tonnes of live blue mussels supplied by aquaculture farmers and about 350,000 oyster spat from the Victorian Shellfish Hatchery are being introduced to the respective sites.
Simon Branigan, The Nature Conservation’s marine restoration coordinator, expects that after about three years the shellfish reefs will stabilise and start to grow.
As well as increasing the bay’s shellfish population, the project is expected to benefit other species providing habitat for a variety of marine life and improving water quality as the shellfish remove excess nitrogen and inorganic materials through filtration.
Similar projects are planned for South Australia and Western Australia.
- Leonie Blain