In 2003 Catalyst reported on a mysterious disease that had wiped out parts of the Sydney Rock Oyster industry. We followed two scientists who were on the trail of how to thwart this oyster killer. Today we revisit this story to find the disease has spread but the there is hope for the future with the development of a disease-resistant super oyster.
TRANSCRIPT
Dr Paul Willis: In 2003 we brought you a story about a mysterious disease that was wiping out the Sydney rock oyster.
We met Bob Drake, a 4th generation oyster farmer on the Georges River, south of Sydney.
Bob Drake: This lease here behind me probably grew about $50,000 worth of oysters a year. Qx slaughtered their crop and they lost their leases, lost their vessels, lost the works.
Dr Paul Willis: The oyster killer was a disease known as QX. Back in 2003 Rob Adlard had been working on QX for nearly 10 years and he had figured out how it kills.
Dr Rob Adlard: What it seems to do is take out the digestive gland, and effectively the oyster starves to death because it can’t then process its food.
Dr. Paul Willis: We also met Dave Raftos an immunologist trying to find out why QX had affected some estuaries, but left others untouched. He focused on a crucial component of the oyster’s immune system, an enzyme called phenyl oxidase.
Dr Dave Raftos: In the Hawkesbury River, which has never been affected by QX disease, phenyl oxidase activity is much higher than it is in oysters from the heavily QX infected Georges River.
Narration: Dave theorised that high levels of phenyl oxidase indicated a healthy immune system protecting the oysters from QX. If phenyl oxidase levels dropped, the immune system would collapse allowing QX to attack. So oysters with high levels of phenyl oxidase, like those on the Hawkesbury River, appeared to be protected against Qx.
But, almost four years on. I caught up with Rob Adlard on the Hawkesbury.
Dr Rob Adlard: I think last time we talked, I was doing a surveillance program. The irony of course is as soon as that surveillance program finished, we had this massive outbreak, especially around this lease we’re sitting on at the moment.
Narration: The QX outbreak on the Hawkesbury River in 2005 wiped out most of the oyster growing areas. Since then Rob Adlard’s team have been trying to find out why the oysters immune systems collapsed and how the disease is transmitted from oyster to oyster.
Dr Rob Adlard: It seems like a, you know, a very large haystack and a very small needle.
Dr Paul Willis: Any hunches as to where it might be?
Rob Adlard: Well, at the moment we’re still fairly keen on polychaete worms that live in little mud tubes in the sediment here We’re finding one, really dominant species, very much associated with oyster leases.
Narration: As Rob tries to find out how the disease spreads, Dave Raftos has refined his theories about the oyster’s immune system and its’ defence against QX.
Dr Dave Raftos: Last time I talked to you, I was talking about a particular gene called phenyl oxidase which we think helps oysters fend off the disease under normal circumstances and the more we look at that gene system, the more we think, yeah, this is critical to developing disease resistant oysters.
Narration: Growing QX resistant oysters has been the job of the NSW Department of Fisheries. Survivors from the George’s River attack were rounded up and crossbred to produce a new ‘super oysters’ that’s currently being trialled by growers on the Hawkesbury.
Robbie Moxham: They’re going really good. We’re very optimistic about it. It’s a fairly long-term project with them but they’ve been through their first infection and they’re growing well and we hope to be growing them in the future.
Narration: It’s been twelve years since QX first struck in the Sydney area. Now a combination of Rob and Dave’s work as well as the new QX resistant “super oyster” will help to put the 33 million dollar Sydney Rock oyster industry back into business.
Topics: Environment, Nature
- Reporter: Dr Paul Willis
- Producer: Paul Schneller
- Researcher: Holly Trueman
- Camera: Lawrence McManus & Dennis Brennan
- Sound: Spiros Mavrangelos & Anthony Frisina
- Editor: Andrew Glover
Story Contacts
Professor Patrick De Deckker
Department of Earth & Marine Sciences
The Australian National Univeristy
Related Info
Department of Earth and Marine Sciences
National Oceans Office AUSCAN Voyage
Dr Dave Raftos
Immunologist
Department of Biological Sciences
Division of Environmental and Life Sciences
Macquarie University NSW 2109
Dr Rob Adlard
Marine Ecologist
Queensland Museum
Rob Moxham
Oyster Farmer
Mooney Mooney
QX facts from NSW DPI Fisheries
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