Species diversification is one way to mitigate against the risk of disease, but it all comes down to practicality and profitability. Can it be easily farmed for a profit?
The Pacific Oyster (Crassostrea gigas), originally from Japan, has been the most popular choice for commercial production based on their fast growth rate and ease of reproduction. The industry consists over 300 family farms in rural Australia and has a farm gate value of $75 million per annum.
Pacific Oysters are, however, susceptible to the Pacific Oyster Mortality Syndrome (OsHV-1 microvariant, POMS) which has caused significant economic impact in Europe, then New Zealand and then Australia in recent years. The key strategies recommended to manage business risk have included the development of disease resistant Pacific Oysters and the development of alternate species for farming (Ausvet 2011; Roberts et al 2013- FRDC 2012/044).
The Western Rock Oyster (Saccostrea sp.) and Native Oyster/Angasi (Ostrea angasi) have been considered an alternative species in South Australia (SA). These species could potentially decrease the impact of POMS by diversifying the SA oyster industry.
In Australia, approximately 30 companies are currently undertaking trials in developing Angasi farming techniques with variable levels of successes. A survey identified the top priorities for Angasi culture were to reduce mortality and develop suitable farming techniques for different environmental conditions and/or locations in Australia.
A project led by SARDI (Prof Xiaoxu Li) and IMAS (Dr Christine Crawford) are utilising CRC-P funding to look into this, including optimised grow-out techniques that will result in healthy and better growing Angasi and develop methods to increase the shelf life of Angasi. The following is an update on the Angasi and Western Rock Oyster experiments to date:
ANGASI – NATIVE OYSTER The spring performance data collected in South Australia for Angasi suggests that there’s a significant difference in both growing location (farms, and exposed and sheltered leases) and techniques (intertidal, subtidal and rotation between them) for optimal growth. Once data has been collected and analysed from consecutive seasons, the results should provide important feedback to industry on the best methods for Angasi production.
In Tasmania, PhD student Deborah Gardner, IMAS has commenced a study investigating farming and processing techniques to maximise production of Angasi. Field trials commenced in November 2018 with wild caught spat to examine growth, condition and survival at intertidal and subtidal, and sheltered and exposed locations on one farm. Preliminary growth data show a number of interesting trends with growing depth/height and location/wave exposure; oysters lower in the water column and at wave sheltered locations have the greatest weight and those higher in the water column have the shortest length shells.
Angasi aquaculture workshops will be held prior to the end of the CRC-P, most likely as part of the August 2019 industry annual R&D events in each state. These forums will provide an opportunity to present the overall project findings and exchange the latest information on Native Oyster aquaculture over the last three years since the last Angasi workshop at SARDI, South Australia.
WESTERN ROCK OYSTER To date the work with the Western Rock Oyster has revolved around assessing biosceure risks from its translocation. The Western Rock Oyster cohabitation trial at the South Australian Aquatic Biosecurity Centre is complete, and pathology samples have been processed for analysis. When cohabited with Pacific Oysters and Native Oysters, Western Rock Oysters showed elevated mortality. The cause of this mortality is not immediately apparent and is under investigation.
For more information on this project, please visit: https://www.oystersaustralia.org/project-2016-807
The author acknowledges that the CRC Program supports industry-led collaboration between industry, researchers and the community. The Future Oysters CRC-P, which focuses on the production of ‘Better’, ‘Healthy’ and ‘More’ oysters, is led by Australian Seafood Industry Pty Ltd in partnership with Oyster Australia Ltd, Select Oyster Company Pty Ltd, Fisheries Research and Development Corporation, Department of Primary Industries and Regions (South Australian Research & Development Institute), University of Tasmania, The Flinders University of South Australia, The University of Newcastle, The University of Adelaide, Commonwealth Scientific and Industrial Research Organisation, University of Technology Sydney, University of Sunshine Coast, Macquarie University, Department of Skills and Regional Development (NSW), and The Yield Technology Solutions Pty Ltd.
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