Nell2005Farming_the_Sydney_rock_oyster.pdf

Fa r m i n g t h e S yd n e y ro c k o y s t e r

A U G U S T 2 0 0 5 P R I M E F A C T 3 , F A R M I N G T H E S Y D N E Y R O C K O Y S T E R

John Nell

Principal Research Scientist
NSW Depar tment of Primar y Industries

The 120-year-old Sydney rock oyster industry in
NSW and southern Queensland is one of the oldest
aquaculture industries in Australia. Sydney rock
oysters, Saccostrea glomerata (formerly known as
S. commercialis) are farmed in estuarine areas and
rivers north (lat. 37oS) up to Hervey Bay Queensland
(lat. 24oS), from the Victoria/New South Wales (NSW )
border and at Albany in Western Australia (lat. 35oS).
However, the natural distribution of Sydney rock
oysters continues on further north from Hervey Bay
Queensland, through subtropical Queensland, across
the tropical north and down the west coast as far south
as Shark Bay (lat. 25oS) in Western Australia. The Sydney
rock oyster industry in NSW directly employed 590
fulltime and 410 part-time people in 2002/03, more
than any other form of aquaculture in NSW. The total
NSW and southern Queensland Sydney rock oyster
production for 2002/3003 was 7,793,390 dozen with a
reported farm gate value of $33.2 million. Production
has been fairly stable at this level since 1989/90.

The oyster industry in New South Wales continues to
restructure, with the number of people with permits
to farm oysters falling from 474 in 1994/95 to 391 in
2002/03. This fall in numbers has been attributed to
producers with little or no production leaving the
industry largely as a result of increasing fees and
charges. In Queensland there were 32 Sydney rock oyster
farmers in 2002/03. This recent decline in the number of
producers has had minimal impact on production.

Farming methods

The Sydney rock oyster industry in NSW and Queensland
is largely dependent on natural spatfall, which has
always been abundant and reliable. It takes the Sydney

rock oyster on average 3½ years to reach Plate size
(50 g whole weight) the most desirable size grade.
Traditionally, the larvae of wild Sydney rock oysters
were caught on tarred hardwood sticks. Oysters are
knocked off these sticks at 0.5 – 3.0 years of age for
growing intertidally on timber frame trays (1.8 x 0.9 m)
with plastic mesh bottoms, which are placed on timber
racks. Alternative growing systems such as baskets and
tumblers are also being used, and some oysters are
grown subtidally on rafts or on floating culture. To reduce
the amount of tarred timber used in the construction of
oyster racks, high-density polyethylene (HDPE) plastic
systems are being developed and used. One example
is the intertidal post supported longline system, with
horizontally suspended plastic tubes of 41 x 91 cm,
developed by South Australian oyster farmers.

Because of reliable natural spatfall, this industry had
not used hatchery technology before 2003. At this time
however results from NSW Department of Primary
Industries’ breeding program using mass selection
techniques showed an 11 months reduction in time to
grow oysters to a market size of 50 g whole weight. This
encouraged industry to consider hatchery technology.

P R O F I T A B L E & S U S T A I N A B L E P R I M A R Y I N D U S T R I E S w w w . d p i . n s w . g o v . a u

N S W D P I

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Figure 1: Timber trays in Cromar ty Bay, Por t Stephens, NSW

2 P R I M E F A C T 3 , F A R M I N G T H E S Y D N E Y R O C K O Y S T E R

Harvesting and marketing

The NSW Shellfish Program (NSWSP) is modelled on the
Australian Shellfish Quality Assurance Program (ASQAP)
and requires that shellfish harvest areas be classified
on the basis of a sanitary survey and the results of an
ongoing strategic water-sampling program. The NSW
program also requires that all oysters harvested in that
state be purified for 36 hours before marketing for
human consumption. With the implementation of the
ASQAP, the requirement for depuration is determined
by the classification of a harvest area. This ensures that
the quality of marketed oysters in NSW is very high.
Live Sydney rock oysters are best stored at 8-10oC and
at this temperature can be kept alive in an excellent
condition for 2 weeks. Opened oysters, however should
be refrigerated at 4oC and have a typical shell life of 7-10
days. The Sydney rock oyster is a gourmet oyster and is
best eaten fresh on the half-shell.

Currently there are no uniform oyster grade specifications
for Sydney rock oysters, however common sizes for
Sydney rock oysters are: Plate, Bistro and Bottle grade
oysters with an average whole weight of 50, 45 and 35
g respectively, which equates to an approximate shell
length of around 77, 73 and 66 mm, respectively. There
has been a gradual decline in the proportion of Plate
grade oysters sold by farmers from 50% in 1994/95 down
to 25% in 2002/03, in favour of smaller Bistro and Bottle
grades. While this trend is to some extent a result of
market forces and disease management strategies, it is
to a large extent determined by a need to maintain cash
flow in this capital and labour intensive industry.

Oysters in Australia are produced for the half-shell
market. Exports of the Sydney rock oysters are still
relatively small and account for <1% of the value of oysters produced. However, the industry is keen to expand markets through export. It is thought that this will have the added advantage of improving the price of oysters on the local market. The implementation of the NSW Shellfish Program will facilitate the development of new export markets in Asia. Research Research for the Sydney rock oyster industry is guided by the 2003-2007 R&D Strategic Plan, which set priorities. Ecological sustainability is vital for the future of the industry. Studies of carrying capacities of NSW estuaries will assist the industry to optimise the stocking of oysters on leases. Research into diseases affecting oysters has developed better detection methods to assist the industry and assists NSW DPI to regulate the movement of oysters between estuaries. It should be noted that people are not affected by oyster diseases. Research is also being undertaken into the effect of research studies include the effect of the environment on the oyster’s immune system. The trend away from Plate size oysters to smaller grades such as Bistro and Bottle grade oysters is a concern for the industry, as it may reduce profitability. The industry is currently developing uniform size grades to help address this problem, aiming to increase sales in the local market and to promote exports. Biofouling of oysters and overcatch (young oysters settling on older oysters) is still a problem for the industry. Currently, this problem is dealt with by a mix of methods, such as leaving oysters out of water for up to 7-10 days to kill overcatch, dipping oysters in around 85oC hot water for 2-3 seconds, immediately followed by cooling in cold water, or culling oysters by hand. All these methods are costly and time consuming. The industry needs a simple and affordable management tool to overcome this difficult problem which would allow the industry to restock currently under-utilised growing areas that are subject to some overcatch. Oyster breeding and hatchery production NSW DPI established a breeding program in 1990 in Port Stephens and the Georges River with the aim of selecting Sydney rock oysters for faster growth. This program was later expanded to include selection for resistance to the two major diseases, winter mortality and QX. Mass selection techniques have been used and oysters selected for five generations in Port Stephens, NSW, now reach a market size (50 g whole weight) 11 months earlier than the average time to market of 3½ years. The program has also been developing oysters that are resistant to QX disease (Marteilia sydneyi) and winter mortality (Bonamia roughleyi). QX disease may kill over 80% of all oysters in the upper reaches of seriously affected estuaries annually. Figure 2: A plate of Sydney rock oysters on the half-shell. Photograph: Ray Alley. 3P R I M E F A C T 3 , F A R M I N G T H E S Y D N E Y R O C K O Y S T E R Unfortunately, while large batches of several million Sydney rock oyster spat have been produced in hatcheries in NSW, the techniques have not been sufficiently reliable for commercial adoption. This has prevented industry from having reliable access to improved oysters. Overcoming the constraints to commercial scale hatchery and nursery production is the research priority in a three-year project supported by NSW DPI, NSW Oysters Farmers and the Fisheries Research and Development Corporation that commenced in July 2003. By July 2004, significant improvements had been made in hatchery and nursery rearing that demonstrated that repeated commercial-scale production Sydney rock oyster spat is possible. Over 10 million spat or 8% of the Sydney rock oyster industry annual requirement were purchased by the industry in 2003/04. These spat were produced from one of NSW DPI’s fast growth breeding lines from Port Stephens. Figure 3: Floating culture in Wallis Lake, NSW Figure 4: O yster growing areas in Australia Map: Francis Dorman 110⁰E 130⁰E120⁰E 140⁰E 150⁰E 160⁰E 110⁰E 130⁰E120⁰E 140⁰E 150⁰E 160⁰E 10⁰S 20⁰S 30⁰S 40⁰S 10⁰S 20⁰S 30⁰S 40⁰S 4 P R I M E F A C T 3 , F A R M I N G T H E S Y D N E Y R O C K O Y S T E R © State of New South Wales 2005 ISSN 1832-6668 Job number 5811 Disclaimer: The information contained in this publication is based on k nowledge and understanding at the time of writing (May 2005). However, because of advances in k nowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currenc y of the information with the appropriate officer of New South Wales Depar tment of Primar y Industries or the user ’s independent adviser. 5 8 1 1 -A u g u st 2 0 0 5 Other oyster fishnotes Dove, M., Ogburn, D., 2003. Oysters and acid sulfate soil pollution. Fishnote, NSW Fisheries, Port Stephens Fisheries Centre, Nelson Bay, NSW, 4 pp. Nell, J., 2001. Diseases of Sydney rock oysters. Fishnote, NSW Fisheries, Port Stephens Fisheries Centre, Taylors Beach, NSW, 4 pp. Nell, J., 2003. Controlling mudworm in oysters. Fishnote, NSW Fisheries, Port Stephens Fisheries Centre, Nelson Bay, NSW, 4 pp. Relevant websites NSW Department of Primary Industries www.dpi.nsw.gov.au Fisheries Research and Development Corporation www.frdc.com.au NSW Farmers’ Association www.nswfarmers.org.au Oyster Farmers’ Association of NSW Ltd www.oysterfarmers.asn.au Further reading ABARE 2004. Australian Fisheries 2003, Canberra ACT, 66 pp. Lobegeiger, R., Wingfield, M., 2004. Report to farmers, Aquaculture production survey Queensland 2002 – 2003. Department of Primary Industries and Fisheries, Queensland, Information Series QI 04027, Brisbane, Qld, pp. 21 – 22. Nell, J,A., 1993. Farming the Sydney rock oyster (Saccostrea commercialis) in Australia. Reviews in Fisheries Science 1, 97-120. Nell, J.A., 2001. The history of oyster farming in Australia. Marine Fisheries Review 63 (3), 14-25. Nell, J., 2002. The Australian oyster industry. World Aquaculture 33 (3), 8-10. NSW Fisheries, 2004. Aquaculture Production Report 2002/03. NSW Fisheries, Port Stephens Fisheries Centre, Taylors Beach, NSW, 21 pp. NSW Oyster Research Advisory Committee, 2003. The 2003-2007 R&D Strategic Plan. NSW Fisheries, Nelson Bay, NSW, 47 pp. Contac t Address: Science and Research Division Port Stephens Fisheries Centre Private Bag 1, Nelson Bay NSW 2315 Phone: 02 4982 1232 Fax: 02 4982 1107 Author John Nell Principal Research Scientist NSW Department of Primary Industries Further information Contact the Port Stephens Fisheries Centre (02) 4982 1232