River health in the spotlight. Is Ag to blame?

Oyster: Canary in a coal mine


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Matt Cardow, Richmond Oysters at Ballina, with Sydney Rock Oysters bred at Port Stephens. The Cardows are part of a trial to introduce a resilient family of oyster to the Richmond River.

Matt Cardow, Richmond Oysters at Ballina, with Sydney Rock Oysters bred at Port Stephens. The Cardows are part of a trial to introduce a resilient family of oyster to the Richmond River.

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Poor water quality in the Richmond has killed a new family of resilient Sydney Rock Oyster leading industry advocates to question: Should one farming industry kill another? But who's to blame - or is it Mother Nature?

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An attempt to re-introduce a family of resilient Sydney rock oysters to the Richmond River at Ballina has failed despite hope that the new Georges River breed would be resilient to QX disease.

Marine vet and advocate for OzFish Dr Matt Landos says the mortality of these oysters is a clear indication of poor river health in the Richmond and he points the finger firmly at agriculture.

All three major rivers on the Far North Coast  – Tweed, Richmond and Clarence –  struggle with low pH and de-oxygenation, much of it related to naturally occurring aluminium sulfate soils. Extensive drainage works in the 1970s are blamed for creating this water quality legacy.

Recent study by the University of New England backs up Dr Landos’ concerns about farming impact with a ‘report card’ issuing an ‘F’ to the Wilsons River which flows through Lismore and carries so much runoff from horticulture that cane growers upriver from Woodburn reported a six inch deposition of red soil on their peat soil flats. 

Jolyon Burnett from the Australian Macadamia Association says much work has gone into improving orchard management with the dual purpose of improving productivity while reducing environmental impact.

Beef production, meanwhile, gets thumbs up for minimal use of chemicals and soil disturbance. However the finger is pointed there with cattle allowed free access to creek banks –  especially on steep creek banks – which contributes to erosion during flood.

What state our rivers?

Sydney Rock Oysters survive where the Pacific Oyster cannot, but struggle with productivity and disease.

Sydney Rock Oysters survive where the Pacific Oyster cannot, but struggle with productivity and disease.

Aquaculture has a serious role to play in the rural community health, according to a recent report prepared by the Department of Primary Industries and the University of Technology, Sydney.

But a new push for better productivity in the $36.8m Sydney Rock Oyster industry, will certainly require greater collaboration between existing land use and estuary farming.

“We need to work together to find way to work in harmony,” says marine veterinarian Dr Matt Landos, currently advising OzFish. “We want to bring oysters back. One industry (agriculture ) shouldn’t extinguish another.”

In the Terranora Inlet on the Tweed River oyster growing has made a comeback after banana production in the upper catchment gave way to urban development –  a damning indictment about water quality on farmed land. Elsewhere on the Tweed and south to the Macleay historic dredging and drainage works combined with agricultural runoff have allowed the mysterious QX disease to cruel a once vibrant oyster industry.

Catchments that don’t have agriculture upstream are able to grow the delicacy –  like the Sandon and Wooli Rivers south of the Clarence.

QX, which seems to thrive in rivers with low salinity, turbidity, poor oxygen levels and other factors, first showed up in the Georges River in 1994.

In 2004 after the worst ever Sydney drought the Hawkesbury also succumbed. Dr Landos suggests the 18 waste water treatment plants that drain into the catchment loaded the rain starved river system with fresh water and nutrients. 

A subsequent proliferation of the water weed salvinea and the deployment of diquat to kill it certainly it didn’t help.

Hawkesbury growers rebuilt an industry using the Japanese Pacific Oyster but in the meantime that species has fallen ill with a global mystery mortality that started in France before moving Downunder. 

Pacific Oyster Mortality has also decimated production in Tasmania while South Australia, which relies on spat from the Apple Isle, is feeling the pinch. South Coast growers of Pacifics are now moving back to the Sydney Rock as their mainstay product.

Camden Haven River oyster farmer Tony Troupe counts himself fortunate in that his estuary, which flows from the Comboyne to the sea past Laurieton is one of the cleanest.

However he says the industry can ill afford to lose production at a time when the market is demanding product.

“If availability shrinks our market will shrink and when we all return to production our market won't be there and we’ll be worse off than in the first place,” he says.

New breed a winner? 

www.theland.com.au/story/4533148/oysters-future-in-the-basket/

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