Outbreaks of QX disease in Port Stephens in 2022 and 2023 mark the continued spread of this disease into Sydney rock oyster (SRO)-producing estuaries in NSW and QLD over the last 50 years. In severe years, QX can cause up to 90% mortalities in affected stock, therefore this disease poses a major threat to an industry that is of substantial economic, historic and cultural value.
Despite the apparent presence of the causative agent (M. sydneyi) in nearly all estuaries undertaking SRO production, disease only occurs in some, and biosecurity protocols further complicate SRO farming as stocks from high-risk estuaries cannot be moved into estuaries that have a lower QX disease risk profile.

Reasons behind the expression of QX disease in some estuaries but not others currently remain unknown. In France, a related parasite, M. refringens, was originally thought to be a widespread cause of marteiliosis in the European flat oyster (Ostrea edulis) as well as mussels belonging to the genus Mytilus. M. refringens O (oyster) type and M (mussel) type, which were originally described due their differential pathogenicities in the respective hosts, have more recently been found to constitute separate species, with M type being renamed as Marteilia pararefringens. A similar situation may exist in Australia with M. sydneyi constituting more than one species and with the more pathogenic strains being responsible for QX disease outbreaks. Historically these questions could not be meaningfully answered due a lack of genetic information about M. sydneyi; however NSW DPI has recently undertaken a genome sequencing project on M. sydneyi that can facilitate strain comparison. Therefore, one aim of this project is to characterise Marteilia strains from estuaries where disease occurs, and compare with those from estuaries where disease does not occur, to better inform biosecurity policies. If the M. sydneyi strains are identical across estuaries, then this may enable biosecurity policy to be modified to allow oyster translocations across so called “high” and “low” risk estuaries. However, if strains do differ across high and low risk estuaries, then any biosecurity policy will be aimed at protecting estuaries not currently experiencing QX outbreaks from the introduction of high pathogenicity strains.

QX disease remains as the primary known threat for SRO production. Due to significant knowledge gaps in how this disease is transmitted, the use of selectively bred QX resistant oysters is the main management tool used to enable cultivation to continue in estuaries where the disease is enzootic. QX survival is a quantitative and a responsive trait where applied breeding offers a good solution to increase QX survival with significant economic benefits for industry. QX survival breeding is reliant on field challenges however, this method works well to increase resistance. Best results for improving QX survival are achieved through a combination of breeding and management practices to minimise impacts. It is recommended to use oysters selected for QX survival as a risk management strategy to reduce stock losses before a QX disease outbreak occurs in an estuary. When oysters selected for QX survival are used in estuaries affected by QX, it is important to deploy spat when M. sydneyi infections have ceased and harvest these oysters prior to a second disease exposure. This relies on specific timing of commercial hatchery production and fast oyster growth which is a trait under selection in combination with QX survival. Field exposures that run over two seasons of QX disease are now used to increase survival following consecutive outbreaks. Other diseases or factors that compromise SRO health prior to or during M. sydneyi infections also reduce the effectiveness of breeding.

Increasing genetic gains for QX survival has been the primary objective of the breeding program since its inception. A genomics project is currently underway which aims to identify genetic markers for QX disease resistance to increase genetic progress for this trait. Batches of Richmond River Rock oyster (RRRO) produced by NSW DPI have shown high levels of of QX disease survival. Prior studies on RRROs suggest that genetically they are classified as SROs but they appear to have developed significant resistance, presumably due to years of exposure to QX in the Richmond River estuary where the disease in enzootic. Preliminary experimental evidence suggests that RRROs display enhanced survival when exposed to QX disease, justifying their inclusion in the selective breeding program. Therefore, the second aim of this project is to assess QX survival of current RRRO families across multiple years of QX exposure and compare these results to other QX-resistant families in the breeding program. This information will be used in this project to formulate a breeding plan to create additional families using batches of RRROs that have been assessed for QX survival.

Translation of research into commercial development is rarely straightforward. In the case of inland saline aquaculture, the research to overcome technical constraints has led to significant commercial development overseas. However, despite significant investment in the 2000s, commercial development in Australia has been slow. This may be due to environmental factors, policy barriers, social and economic conditions at the time. Some of these possible constraints have completely changed in the last two decades and there is currently new interest in inland saline aquaculture. This project is required to help ensue potential investors are armed with as much information as possible. What did previous research into inland saline aquaculture find? What prevented commercial development in Australia and what led to development overseas? What are the new opportunities and how can they be supported?

The current National Guidelines were developed through the FRDC (Project 2010/061) with recognition of the need for a coordinated, nationally consistent approach to establishing harvest strategies for Australian fisheries. At this time, the Commonwealth Harvest Strategy Policy and Guidelines (2007, now updated) provided a foundation for harvest strategy development in Commonwealth managed fisheries, however implementation of the key elements of harvest strategies (defined objectives, indicators, assessments, reference points, trigger points and decision rules) varied across jurisdictions, and gaps remained for data limited fisheries.
Similar to the proposed project, the AFMF and FRDC recognised that support for development of harvest strategies could be improved through development of the National Guidelines that focused on less developed areas of harvest strategy policy, including cross-jurisdictional and recreational management arrangements, and incorporating quadruple bottom line (ecological, social, cultural and economic) analysis into fisheries decision making.
As harvest strategy policy and incorporation of quadruple bottom line ecologically sustainable development (ESD) principles have increased as management priorities, harvest strategies have sought to incorporate increasingly challenging issues, in many cases continuing to use disparate approaches between jurisdictions that arguably hold the same objectives and responsibilities, as well as potentially competing interests.
In many cases, harvest strategy policy and development has been held back from achieving quadruple bottom line objectives due to a lack of consistency in the outlook and approach between jurisdictions, and available guidance for dealing with the complexities associated with multi-species, multi-sector or multi-jurisdictional issues. With significant developments occurring around traditional fishing and management, progressing the inclusion of cultural fishing specific objectives is also required.
In addition, the review provides opportunity to address broader issues including the relationship and function of harvest strategies in association with shared access with competing users, cultural interests, ecological issues (e.g. habitat degradation, pollution and climate change), and marine conservation areas, as well as options, incentives and trade-offs for improving data, monitoring and assessment in data poor fisheries or sectors.
The proposed review will ensure the National Guidelines remain a prominent, independent and contemporary guide for fisheries jurisdictions, managers, researchers, fishers and stakeholders in supporting the review of harvest strategy policy frameworks and the development of harvest strategies that in many cases seek to resolve complex issues and balance competing interests.
To achieve this, the proposed project aims to:
1. Review and update the National Guidelines to Develop Fishery Harvest Strategies to ensure the National Guidelines are consistent with current harvest strategy utilisation, address contemporary fisheries challenges and the most up to date information available;
2. Take stock of harvest strategies in Australia (by jurisdiction) and internationally, including how many fisheries now have operational harvest strategies adopted and those under development; and
3. Produce a report with the updated National Guidelines coupled with a detailed communication plan and associated materials to promote and communicate the outcome of the review with all stakeholders.