Weeds don’t just threaten land-based primary production systems, they are also a risk to the productivity and quality of Tasmania’s aquaculture industry.
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A particularly aggressive aquatic weed is rice grass (spartina anglica), originating in the United Kingdom and introduced to Tasmania more than 50 years ago.
When Landcare volunteers and primary producers collaborate to solve a common problem, it can have a positive multiplier effect for us all.
- Tom O'Malley
It inhabits the mudflats and banks of estuarine environments across northern Tasmania, with particularly severe infestations in the Rubicon and Tamar river regions.
Duck Bay and its estuaries near Smithton are also under threat, but thanks to the work of the Circular Head Landcare Group, in cooperation with local land managers and industry, this area is at the forefront of an ambitious eradication program.
The group’s work is being closely followed and supported by local commercial oyster producers, who depend on the exchange of tidal waters and a healthy ecosystem to sustain their stock.
John Poke has been farming oysters in the area since 1979 and recognises the importance of rice grass control, not only in preserving the Duck River’s recreational and environmental values, but also the economic health of far North-West Tasmania.
“As the rice grass takes root and spreads to form meadows, sediment is trapped and the river banks build up,” Mr Poke said.
“This build up reduces the volume of water that is exchanged on the tides, reducing the food available for the oysters.
“It also can result in only a small access channel. That has the potential to reduce the depth too and prevent our vessels from moving up and down the river,” he said.
The Circular Head Landcare Group is four years into a 10-year eradication program.
The invasive nature of rice grass requires a solid follow-up program once initial spraying or manual removal efforts have been implemented.
The importance of keeping control of the rice grass incursion in Duck Bay was highlighted with the arrival of Pacific Oyster Mortality Syndrome (POMS) in Tasmania’s Eastern waters during 2016.
During the outbreak, oyster farming in the pathogen-free Duck Bay increased to help meet supply requirements.
Oyster farmers worked closely with the Landcare Group throughout this period, and the resulting strong relationships continue to assist the planning and timing of today’s rice grass control efforts.
This example of weed control demonstrates how the economic, social and environmental benefits of any habitat are closely linked.
When Landcare volunteers and primary producers collaborate to solve a common problem, it can have a positive multiplier effect for us all.