richmond river oysters

Project Background

Forty-five years ago, full-cycle (spat to harvest) oyster farming ceased on the Richmond. Various hydrological changes to the  Richmond catchment has resulted in poor water quality which triggers the problematic QX disease in oyster populations[JL1]. Oyster farming from southern QLD through to the south of Sydney continues to suffer from the disease, experiencing severe crop losses and industry downturn.

OzFish Richmond River Chapter members are working with local oyster growers to better understand the local shellfish population.  By 2015, when the projects started, monitoring records showed an almost total disappearance of the estuary’s Sydney Rock Oyster (S. glomerata) (SROs).

How is OzFish volunteers helping?

More recently oysters on the Richmond appear to be in regeneration mode but have taken on a slightly different appearance to that of a close cousin, the Sydney Rock Oyster. Scientists are referring to them as Richmond Unknown Rock Oysters (URO).

During OzFish monitoring in 2016, the URO’s made themselves quite conspicuous among graveyards of dead Sydney Rock Oysters. OzFish brought this to the attention of a local oyster that was in the process of dismantling his lease. His observation was that they looked like a northern Black-Lip oyster. The oysters had a distinctive pigmentation at each end of the adductor muscle, which is not seen in SRO’s.

richmond river

Have we found a Qx resistant variation to Sydney Rock Oysters (S.glomerata)?

richmond river oysters

A darker coloured shell…

The RRO was found during OzFish monitoring efforts when fresh wild spat falls in the estuary, along with scattered one to two-year-old oysters that had survived the significant floods and poor water quality of summer 2017.

It was observed by a local oyster grower while dismantling his lease, that these few surviving adults were slightly different looking oysters and could be a variety of northern Black-Lip.

The oysters had a distinctive pigmentation within the shell beneath the attachment of the adductor muscle, which is not seen in SRO’s.

 The news of the Richmond River field trials spread through the industry and raised huge interest, particularly in the areas most affected by the Qx outbreaks.

Further research is needed

OzFish is continuing to report significant wild oyster growth back in Richmond. The Chapter is interested to continue this project for benefits on several fronts.

  • To better understand the science behind their resilience to QX disease in turn significantly benefitting the oyster industry.
  • To see oysters once again populate QX plagued estuaries (including Richmond) with both farmed and wild oysters providing essential habitat to several species of fish.

Collaborating scientists Dr. Carmel McDougal (Griffith), Dr. Kirsten Benkendorff (SCU) and Dr. Jan Strugnall of James Cook University have indicated significant interest in pursuing research and would like to explore our URO’s further.

Funding is dependent on this research going ahead

1. Investigate the correlation of pigmentation with QX resistance.

The URO’s have darker pigmentation (of both the shell margin and the adductor muscle scar) than traditionally farmed SROs (as seen to the right here).

Melanisation is known to be associated with immune responses and it is possible that there is a link between this pigmentation and parasite immunity.

An honours project can be conducted to investigate whether there is any correlation between measured levels of pigmentation in SROs and QX incidence.

richmond river oysters

2. Population genetics of wild Richmond River oysters

COI barcoding has demonstrated that the Richmond River oysters are S. glomerata.

It is apparent that this population has undergone a significant bottleneck and is currently re-establishing, which may mean that there are notable genetic differences between this population and those found elsewhere.

A population genetic study could be conducted to compare the genetics of the Richmond River population with those found elsewhere.

3. Molecular mechanisms of QX resistance

Even within standard hatchery-bred Sydney Rock Oysters variability is observed in QX infection rates and mortality.

There is an option to investigate potential molecular mechanisms of QX resistance using a combined transcriptomic and proteomic approach. The Richmond River oyster population (hatchery bred lines if possible) and co-located standard hatchery-bred stock will be monitored for QX using a PCR-based approach.

This research will identify genes and isoforms that are specific to individuals that are resistant to QX, providing understanding about the mechanism of this resistance and possibly identifying genetic markers for resistance.

richmond river oysters

Latest News

APRIL 2020 | New Oyster variety potential game changer

For the past several years, committed recreational fishers from OzFish Unlimited’s Richmond River Chapter, have been working with scientists from the NSW Government and Universities to bring back shellfish to the Richmond River. The research, underway since 2016, has identified Rock Oysters that are thriving within the Richmond estuary and showing resistance to a fatal oyster disease that could be the breakthrough oyster farmers and the river desperately need.zFish volunteers have put in hundreds of hours monitoring oysters with the support of NSW Department of Primary Industry – Fisheries, Southern Cross, Macquarie and Griffith Universities. Shellfish reefs are one of Australia’s most critically endangered marine ecosystems. Natural wild shellfish reefs in the Richmond have sadly disappeared over the past five decades, along with a once thriving oyster industry.

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SEPTEMBER 2021 | Baby oysters a promising sign for the Richmond river

One fine spring morning, some members of the Richmond River Chapter cruised over to their local oyster lease to inspect the lease to find a single catching rack filled with tiny oysters. The recreational fishers got excited as they collected the little gems for further inspection. These fishers are on the brink of a scientific discovery that could resurrect the oyster population in what has been dubbed by some as the ‘worst river in New South Wales’.

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The Richmond Rock Oysters project has been supported by the following project partners