Two years we have waited! This week finally marks the end of the spat shortage for our farm as we adopt thousands of 4mm Pacific Oyster babies... straight from one of the newly established hatcheries on Eyre Peninsula South Australia.
Many years ago, Pacific Oysters (Crassostrea gigas) were introduced to dozens of countries (including the UK, France, USA, Canada, Korea, China and New Zealand) for aquaculture purposes. In Australia, Pacific Oysters were introduced deliberately into Western Australia and Tasmania in 1947, into Victoria in 1953 and into South Australia in 1969. The Pacific Oysters that were introduced in Tasmania and Victoria successfully spawned, however those introduced to Western Australia eventually died out.
Like most oyster species, Pacific Oysters change gender during their life, usually spawning first as a male and later as a female. Spawning is temperature dependent and generally occurs in the summer months. Female Pacific Oysters can produce up to 40 million eggs per spawning, giving the surrounding water a milky appearance. Fertilisation takes place in the water column.
The larvae are planktonic and free swimming, developing for three to four weeks before finding a suitable clean hard surface to settle on (at this stage they are called a spat). A very small percentage of oysters survive this phase in the open water. To maintain sufficient supplies of Pacific Oysters in Australia, hatcheries were set up to fertilise and protect the spat and grow it to a size that would provide the best survival when moved out to a farm. Hatcheries are usually land based and provide controlled environments for spat to grow. South Australia now has three hatcheries in Eyre Peninsula providing spat to the SA Oyster Growers industry.
These babies left their tanks at the hatchery on Eyre Peninsula and travelled on a truck to Adelaide Monday night, were picked up by Kenny early Tuesday morning and brought over to the island by ferry.
Our crew then carefully measured them into mesh bags at densities to ensure maximum growth. The bags were then taken out to the nursery section of our farm and hung on the lines. Now they are gently rocked to sleep as the tides sweep in and out for a few weeks until we bring them in for a grade!
Once moved to our farm at about 4-6mm, Pacific Oysters take about 18 months to grow to the first saleable size for wholesalers which is a 50-60mm top shell 'Bistro' size. Pacific Oysters can live up to 10 years and reach an average size of 150-200 mm.
We look forward to growing these babies up to be fat, succulent Kangaroo Island Premium Oysters for next season!