Ground Cover Issue 60 - February/March 2006
01.03.06
Fish farming floated for saline farms
Issue 60, February - March 2006
The problem of wheatbelt salinity may be turned into a commercial opportunity. By Geoff Wilson
An innovative water-treatment process has revived interest in using farm dams that have turned saline into inland saltwater fisheries.
About $1.4 million is being spent near Northam in Western Australia on research and development of a new aquaculture production technology called the Semi- Intensive Floating Tank System (SIFTS). The developers believe they will have a commercial version of the system available to salt-affected farmers within 12 to 18 months.
[Photo (left): The floating tank system in operation in a two-hectare irrigation dam in Mildura, Victoria. The liner on the rear tank has been inverted, swimming the Murray cod via a channel into the transporter tank.]
The idea is to turn a problem into an opportunity by helping broadacre farmers diversify into aquaculture, which is regarded as one of the fastest growing primary industries worldwide.
The idea of using saline farm dams for raising saltwater fish was first raised in WA about 10 years ago, but economic returns were difficult to achieve because yields were limited by excessive water-fouling by fish wastes in the confines of a farm dam.
The SIFTS concept seeks to address this. It is a floating tank system that collects fish wastes and pipes it ashore. It evolved from a home swimming pool protection device invented by Ian McRobert, managing director of McRobert Aquaculture Systems in Welshpool, WA.
His basic concept was the starting point for research and development by Challenger TAFE's Gavin Partridge and Dr Gavin Sarre of C.Y. O'Connor TAFE in Northam, in conjunction with McRobert Aquaculture Systems.
The two TAFE researchers and their industry partners have since shown that the SIFTS 'extensive aquaponics' system can grow about 26 tonnes of fish per hectare of farm dam a year, five times more than what was previously achievable. Aquaponics is a technology pioneered in North America in which fish wastes in intensive aquaculture are used to grow plants. Further research has now been started into finding and proving economic uses for the solid fish wastes collected by the SIFTS.
The SIFTS system uses air to circulate and aerate water in the floating tanks. The same air pressure is also used to drive a no-handling fish harvesting system.
Fish species that have been tested in the system include mulloway, snapper, saltwater trout and barramundi. The trout and barramundi have been the best performers - taking only 14 weeks to grow from 100 grams to plate-sized 500 to 700 grams.
The new waste-utilisation project is also being led by the TAFE Partridge and Sarre team, together with Murdoch University researchers Dr Alan Lymbrey, Dr Rob Doupe and Gavin Kay, who will study using fish wastes to grow salt-tolerant crops being developed by NyPa Australia Ltd.
NyPa was formed in 1993 to import and evaluate salt-tolerant plant species bred from plants collected in north and central America, and to develop salinity solutions generally.
Dr Doupe says the practical outcome from the research will be to find out how NyPa grain and forage crops respond to fish wastes with variable salinity and nutrients.
"We will be looking at how constructed wetlands models can be used for cultivated forage crops using saline fish wastes," he says. "Trials at Murdoch University are already showing that we are removing up to 80 per cent of the salt and about the same proportion of nitrogen and phosphorus. Further modelling is needed to understand the role of soils, sediment and plants."
Mr Partridge says further increases in SIFTS productivity through secondary crops and waste re-use should be possible. "These include production of artemia, a brine prawn fish feed, oysters and salt-tolerant crops that can be irrigated with seawater."
Of the A$1.4 million budget over three years, $660,000 has come from Australia's Fisheries Research and Development Corporation. The balance comes from the Wheatbelt Development Commission of WA ($100,000), a farm owner with saline groundwater, Stan Malinowski ($100,000, plus in-kind contributions) and from in-kind support of others such as McRobert Aquaculture.
The new research into SIFTS is complemented by McRobert Aquaculture's own development of low-stress fish grading technology.
Mr Partridge says it is not yet known how many WA graingrowers might take up SIFTS technology on their properties. "Although there are more than a million hectares of salt-affected land in Western Australia and therefore many potential water sources for SIFTS, not all are suitable for aquaculture.
"However, we would be well on our way towards initiating a new wheatbelt aquaculture industry in WA if SIFTS users are collectively producing from 500 to 1000 tonnes of fish within the next five years."
He says that while the SIFTS system could contribute to developing an aquaculture industry in the WA wheatbelt, a larger potential exists for irrigation dams as an 'extensive aquaponics' part of a larger integrated agri-aquaculture system being developed in Australia. The Australian cotton industry, for example, has around 1000 farm water storages suited to SIFTS and other systems of raising fish that use their wastes for horticulture.
For more information: Gavin Partridge, 08 9239 8032; NyPa, www.nypa.com.au/
