Oyster farmers tap American know-how
Technology that accelerates the growth of juvenile shellfish proved a popular workshop subject when US expert Dale Leavitt met with Australian oyster growers
Photo: Ana Rubio
By Gio Braidotti
In a whirlwind two-week tour of Australia’s oyster-growing estuaries, American researcher Dale Leavitt met with more than 200 growers in New South Wales, Tasmania and South Australia. In the process, he provided workshops on a shellfish farming technology popular in the US but yet to be widely adopted by Australian producers – the floating upweller system, or FLUPSY.
Having grown up a fisher and wild shellfish harvester in Maine, Dale Leavitt said during his visit that he felt a deep camaraderie with the Australian farmers he met, and he also fell in
love with the wildness of Australia’s coastlines and countryside.
Based at the Roger Williams University in Bristol, Rhode Island, and having been a farmer himself, Dale Leavitt works closely with shellfish growers and provides extension services to
Director of the NSW-based Select Oyster Company Ana Rubio helped to coordinate Dale Leavitt’s visit, which was sponsored through an FRDC travel fellowship. Because of his experience, he was able to talk about a range of issues of interest to growers including the use of oysters to remediate polluted waterways, cultivation of alternative shellfish species and industry extension programs.
Photos: Dale Leavitt
But it was the topic of his July and August workshops – the FLUPSY – that generated the most interest among growers. Dale Leavitt explains that upweller systems are located in oyster-growing waterways and use water flow to nurture and accelerate the rearing of healthy juvenile oysters to a size big enough to farm.
As such, they can provide a handy transition from the hatchery stage, where spat are produced, and the grow-out stage, when the oysters are farmed.
“The feature that interests farmers is that it promotes a quick growth stage because of the way the water flows through the shellfish and replenishes the oysters’ food supply,” Dale Leavitt said.
In the US, a 25-millimetre oyster can be reared to grow-out size in a FLUPSY in about six weeks. “That’s because upwellers are a pump system that deliver a lot more food to the animals than if they were placed in baskets or trays,” Dale Leavitt said.
The extra nursery stage also allows for better adaptation to the wild environment of the farm, so that the oysters are healthier and can better withstand conditions in the estuary, including diseases.
While the original concept was developed in the UK, FLUPSYs have been extensively adapted and adopted in the US. They are now used by 95 per cent of oyster farmers on the north-east coast. They are also used to cultivate other shellfish, such as clams and scallops.
“It is widely recognised as being an effective and popular technology for nursery culturing of oysters in the US,” Dale Leavitt said.
He described the technology as simple and affordable. It is the kind of device that canny farmers can easily construct themselves. The tricky issues relate to water flow rates and seeding densities – issues that Dale Leavitt has researched extensively.
“If farmers were to build a regular electric powered upweller from scratch, it is going to cost about US$3000 [A$3385] – more if they want the solar option,” he said. “That’s a perfectly reasonable cost.”
There are three basic features to a US$3000 FLUPSY. First, there is a floating raft. Embedded within the raft – hanging down into the water column – are a series of small containers, called silos, that have solid sides and a mesh on the bottom small enough to hold oyster seed. Each silo then has an outlet pipe that inserts into a trough located in the middle of the float where a pump continually pumps water back out of the trough.
The pump creates a water level differential between the inside of the trough and outside in the silos where the shellfish are held. That pressure difference induces a flow of water up through the bed of shellfish and then out the discharge pipe into the centre trough where the water is then pumped back out.
“They are called ‘upwellers’ because the net water flow goes from the base up to the top of the column of shellfish seed,” Dale Leavitt said. “You have to custom-make the silos and centre trough but everything else you can buy off the shelf, including the pump.”
All the information Dale Leavitt made available at the Australian workshops has been converted into PDF files that can be viewed at the Select Oyster Company website, Ana Rubio says.
A ‘how-to’ kit that describes how to build a FLUPSY especially suited to Australian shellfish producers is also being prepared for the FRDC. “There is a huge amount of interest in the technology,” Dale Leavitt said.
“Everywhere I went people asked for specific information because their intention is to build one and test it out sometime in the next year. What attracts them is the same thing that attracted me to do this research – the potential for commercial efficiencies. It leads to better outcomes for their business.”
He said he found the contrast between operations in the US and Australia interesting. “From a technological standpoint, the US maybe has a little better grasp on hatchery development and nursery operations. But the Australians definitely have the leg-up in terms of grow-out technology.”
He cites the example of Australian growers’ use of the basket culture system for growing oysters in suspended culture. “That is something I don’t think many of our US growers had thought about as they mostly grow oysters in racks on the bottom,” he said.
NSW growers consider joint venture
The idea of building a shared floating upweller system (FLUPSY) to improve the production of Sydney Rock Oyster (Saccostrea glomerata) spat is being considered by some New South Wales oyster growers.
Ana Rubio is a director of the NSW-based Select Oyster Company (SOCo), which was established by the NSW oyster industry in 2004 to commercialise new lines of Sydney Rock Oysters, particularly those with improved disease resistance. However, she says production of spat by the hatcheries involved in SOCo has struggled to keep up the supply.
A single FLUPSY system would have capacity to grow out more spat than any single oyster producer is currently able to secure.
Following the visit by Dale Leavitt and workshops detailing the FLUPSY technology, she says growers in several regions have discussed with her the possibility of a jointly operated system in their estuaries.
“If hatchery production increases and becomes as consistent as the supply of Pacific Oyster (Crassostrea gigas) spat is in Tasmania and South Australia, it might be more economically viable for individual businesses to have their own nursery systems,” she says. “But there is simply not enough hatchery-reared Sydney Rock Oyster spat for that at the moment.
“Working together, growers farming in the same estuary would be able to share the costs, and the capacity of a FLUPSY.” She says some nursery operators in NSW are also interested in the technology to replace or to add to the land-based upwellers they use.
FRDC Research Code: 2008-328.20
Dale Leavitt, email@example.com
Ana Rubio, firstname.lastname@example.org