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
This article was originally published in the VOICES FOR THE EARTH column in The Daily Examiner on March 19, 2018.
For more information on the commencement of this project, see The Nature Conservancy's Vistoria's biggest ever reef restoration project hits the water.
