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Volume 27 No 1 – Autumn 2013

Closing in on whiting crop Lessons learnt in ornamentals Gold Coast farmer heads north Pearl passion fuels expansion Abalone farmer’s steady harvests Oyster farmers to rise from ashes Pedigree prawns a game-changer Purging effects on yabbies

P RI NT P O S T A P P ROVED NO 768108–00002

I SSN 0818– 5522





Dr Tim Walker Regular contributors David O'Sullivan Tracey McKean Subscription/editorial Austasia Aquaculture PO Box 658, Rosny, Tas. 7018 Ph: 03 6245 0064 Fax: 03 6245 0068 Email: Advertising Megan Farrer Design/typesetting Coalface Production Pty Ltd Prepress & Printing Geon Group Copyright © by Austasia Aquaculture.

8 24

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Bountiful whiting harvest tantalisingly close


Aquaculture caught in the headlights with disease


Harvesting marine ornamentals and shrimp from lessons well learnt


Oyster farmers to rise from the ashes


A survivor’s tale


Gold Coast Marine Aquaculture heads north


The power of passion for pearls


Abalone farmer settles down to steady harvests



Pedigree prawns


Purging effects on yabbies (Cherax albidus): does purging produce a superior product?


Autumn 2013 | Austasia Aquaculture 1

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Aerial view of Coral Coast Mariculture’s farm at Littabella Creek showing the mouth of the creek.

Bountiful whiting harvest tantalisingly close It sounds like aquaculture heaven: >


pristine warm saltwater flowing



the technical know-how are very sound. There is a growing market in

past your property frontage,

has 25 hectares of licensed production

Australia and a hungry market in the

the most stable temperatures in

ponds, a 12 hectare settlement pond

U.S.A., the home of the soft shelled

and is situated 3 kilometres from the


all the research done and commercially tested,


no.2). The academic knowledge and

oral Coast Mariculture (CCM) owns such a farm, freehold. It

the country, >

Property and prospects

mouth of Littabella Creek, north of Bundaberg in Queensland.

“It’s all pretty straight forward,” says Clive. “The system works very well. It

“We can grow just about anything,”

just needs a little bit more infrastruc-

all the necessary permits and

says Dr Clive Keenan, Managing

ture to be commercial. We even have

licences obtained,

Director of CCM, “tropical species,

self-cleaning tanks.”

farm ponds with concrete sides and sandy bottoms just waiting

saltwater species and freshwater. The

However Clive now believes grow-

micro-climate around this area is one

ing whiting may well be the future for

of the most stable in Australia.” The

the farm.

for stock,

lungfish is offered as validation. “It has

Currently, CCM are running test


a hatchery facility with lab,

been in this region for the last 300 mil-

ponds on two species of whiting,


three 0.1ha concrete lined

lion years,” Clive laughs. “That’s got to

Summer or Sand Whiting (Sillago cili-

show you how stable the climate is

ata) and the Goldenline (Sillago



nursery ponds with room for more, >

bio-remediation in place for

Previously, Clive’s focus, and that of

There’s one three-hectare pond

CCM, has been on culturing soft

stocked with fingerlings and a nursery

a crab moulting facility, and

shelled blue swimmer crabs (Portunus

pond stocked with fingerlings.

a huge supply of freshwater.

pelagicus). He has done extensive

And the team is achieving good

research and growout with this spe-

results; the whiting can be grown to

waste water, > >

It’s an aquaculturist’s dream, right? Yes, but only if have the cashflow to run it.

cies, both overseas and in Australia

330grams in a low-density stocking

with the Queensland DPI at Bribie

scenario, with a projected harvest of

Island and at the Littabella Creek farm


(see AA Vol.19 no.6 and AA vol.22 4 Austasia Aquaculture | Autumn 2013

“With this method, the inputs are


very minimal,” says Clive “and we are using an imported specialist feed.” The plan is to have 20 hectares of whiting ponds leaving the rest for crabs. “We hope to stock those ponds with whiting at 10t/ha, that will give us 200t per year. We anticipate providing the various markets with a total of 4t of fresh fish a week. “We could probably grow crops at greater densities and produce a lot more fish. It’s a beautiful eating fish, it’s an accepted fish but the market still needs to be developed more. With farming the fish we can overcome the market’s problem of inconsistent supply and variability of size.” Markets are available in Brisbane, Sydney, Melbourne and locally. Prices paid range from $14 to $22/kg for large 25 to 45cm fish. Coral Coast Mariculture will be able to grow whiting all year in the sand-bottom ponds. Stocked with whiting, the ponds are operated on a low biomass basis with a gentle continuous-flow exchange system. At 2m deep, the pond environment is very stable with respect to temperature and being so close to the mouth of the creek allows access to good quality, saline waters. The farm also has a very large freshwater impoundment, so freshwater is not a problem and salinity can be controlled. Further opportunities “The other opportunity that exists,” says Clive “is that we believe we can grow whiting in the same ponds as Caulerpa lentillifera. The conditions here are perfect for growing this seaweed.” Caulerpa is known in Australia as sea grapes or green caviar. It is a very attractive vegetable with gleaming translucent jewel-like beads. It feels good in the mouth, crunches slightly when chewed and bursts with flavour. As an edible garnish or salad ingredient, it complements many seafoods and works well in vegetarian or vegan dishes. It is becoming an ‘it’ ingredient for foodies. Well known chef, Alastair McLeod is

From top: In the hatchery, Clive Keenan checking whiting breeders in a 5000l Duraplas tank. In the background are 10t Ajay fibreglass parabolic tanks used for larval rearing of various species. Kel Gordon, hatchery manager, inspecting 10t Ajay fibreglass parabolic tank after spawning has occurred.

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Autumn 2013 | Austasia Aquaculture 5


quoted as saying “green caviar has just what you want as a cook” in an article in the Courier Mail (August 24, 2010). “What we’re looking to do,” says Clive “is farm with a low environmental impact with a high production value with less stress on workers.” Multi-species hatchery On the Littabella Creek farm site, Clive also runs a hatchery. Kel Gordon is his hatchery manager. From this hatchery CCM have spawned all of the various fish species (Australian Bass, Macquaria novemaculeata, Barramundi, Lates calcarifer, Silver Perch, Bidyanus bidyanus, Summer or Sand Whiting, Goldenline Whiting), crabs and Black Tiger Prawns, Penaeus monodon, with which they have stocked their ponds. Kel conducted the research on the breeding of the two species of whiting used in the successful test ponds. As part of the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) native fish fingerlings initiative, CCM’s hatchery permit also allows them to spawn wild-caught breeders to provide fingerlings to restock fishing impoundments and recreational fishing areas. In this role Australian Bass and south-eastern strain Barramundi are produced.

From top: James Mitchell, pond worker, with net containing “green caviar” seaweed for planting. Sea grape or green caviar seaweed, Caulerpa lentillifera.

6 Austasia Aquaculture | Autumn 2013

Makings of a cash crunch When the company first formed, it purchased a large seafood processing complex at the Port of Bundaberg (Burnett Heads). This property includes offices, cold storage, a blast freezer, a boat fuelling facility and a 36-berth marina. There’s DPI&F Aquaculture Development Approval for a farm and hatchery at the site (AA vol.22 no.2) as well as a government grant. The complex is also fully AQIS licensed and is to be part of the Mariculture Park. The challenges started for CCM when lease agreement negotiations with the Bundaberg Port authority stalled. The long delay not only cost much money; it was then followed by an unreasonable increase in rent.


Clockwise from right: Trials for maturing crabs in a recirculating system. 9m high foam fractionator, part of the water treatment system for the moulting facility. The crab moulting facility with very large foam fractionator and 200 tonne receiving tanks in front.

To top that off, the grant money had an expiry date. The company had to start farming or lose it. So when the Littabella Creek farm site became available, and with no end to the lease fiasco in sight, a quick decision to purchase was made and tenants put into the processing facility. That meant the Port facility was no longer needed and it was put up for sale. A contract was signed with a willing buyer but then the Global Financial Crisis struck and, like many deals at that time, the sale fell through. Over the last two years Clive and his team have had their hands tied by a subsequent sale contract and have been unable to put any commercial crops through. This contract has restricted them to doing trials. “We’ve been twiddling our thumbs whilst conducting research for the last two years. We’ve been in this limbo situation,” Clive explains. “We had $2million invested in the company. The farm was bought for $1million.

If we hadn’t bought the Port facility we would be sitting here with plenty of money to operate the farm without debt. You need a million dollars to grow the two million.” That second sale contract has now fallen over and CCM finds itself fighting to put crops through. Solutions So, Coral Coast Mariculture owns a beautiful property near the mouth of Littabella Creek and a processing plant at the Port of Bundaberg, Burnett Heads. It has experienced and enthusiastic staff, the capability and ability to produce multiple species crops but has no cash-flow to put product through ponds. Not an unheard of scenario in aquaculture circles. In an effort to raise operational capital and get the farm producing, CCM has again put its properties up for sale through Ray White. Possible avenues are buying either the processing plant or the farm

outright, buying in as a partner or purchasing shares. “The valuation for both properties is $5.47 million,” says Clive. “You could buy the whole farm or you could buy in as a partner. Our preferred option is to sell shares in the company; it’s a lot cleaner way to buy it and there are more options. You can buy a percentage of the shares, so you don’t have to buy the whole lot.” By Tracey McKean For more information contact: Dr Clive Keenan, Managing Director, Coral Coast Mariculture, PO Box 7333, North Bundaberg Q4670, P: 07 4156 1600, M: 0402 482 588, E: ccm@bordernet. Postscript: Whilst the Bundaberg region was hard hit by the flooding from ex-cyclone Oswald, Coral Coast Mariculture’s ponds at Littabella Creek have remained intact and above the floodwaters

Autumn 2013 | Austasia Aquaculture 7


Harvesting marine ornamentals and shrimp from lessons well learnt Ornamental fish are great as a training tool – usually they are cheap, hardy, colourful and easy to breed so students get the unique opportunity to learn about husbandry and breeding practices. Working with marine ornamentals can significantly increase the difficulty factor, and adding shrimp further complicates things. However, staff and students at a Western Australia institute are producing more than nine species for sale throughout Australia.


urack Institute of Technology is the major provider of vocational education and training in the Central West region of WA. Durack has five campuses throughout the Mid-West & Gascoyne regions delivering training for students in a diverse range of careers in the seafood, marine science, marine tourism, maritime transport and mining industries. The Batavia Coast Maritime Institute (BCMI) in Geraldton is a state of the art training, research and development facility covering 2.7ha of land. Completed in 2006, it has a student amenities area, com8 Austasia Aquaculture | Autumn 2013

puter lab, teaching classrooms, laboratories, maritime simulator room, aquaculture hatchery, marine ornamentals production area, NATA-accredited environmental testing laboratory, horticulture and CALM greenhouses, aquaponics and hydroponics demonstration facilities. BCMI also operates a 20m marine vessel named the Masterclass and numerous smaller boats that are used for fishing, maritime and aquaculture courses. A wide range of separate recirculating and flow-through culture systems are maintained for different projects includ-

ing some stock enhancement work around Geraldton with aquacultured Black Bream (Acanthropagrus butcheri) for the recreational fishing group RecFish West. “We’re also working with a ‘live rock’ aquaculture company (Bada Mada Pty Ltd),” explains BCMI Training Director Dr Suresh Job. “And we are expanding our ornamental production. All-in-all we have some fantastic equipment and systems for our students to work with and any projects with commercial groups are a real bonus.”


System overview “All seawater coming into the site is through a 500m long ocean intake line which sits in about 6m of water,” says BCMI Research and Development Officer Dr Colin Johnson. “This is filtered to 50µm through two 3.5KL Chadsen sand filters and all waste sea water is filtered through two Signature 2000 Fibreglass sand filters to 50µm before disposal down a saline bore. “All our backwash water is collected in a settlement pond with a surface off-take from this pond leading to a separate saline bore. The settlement pond is then drained and vacuumed every two years and sediment removed to Shire Council tip.” Hatchery water (also used to replenish the ornamental systems) is further filtered to 1µm with a series of bag filters then foam fractionated (Aquamedic Turboflotor 10000) and UV-sterilised (Emperor Aquatics Lifeguard Smart HO 02503002). This water is diverted to two 60,000L tanks with an option to heat or chill this water with a Solar Wise unit to specific temperatures if required before feeding into the hatchery.

have been laid and begin to develop towards hatch. Dottybacks are provided with 25mm PVC pipe sections in which to lay and cohabitation of broodstock these two species appears to have little effect on reproductive output. “Our broodstock are a mix of purchased wild collected and tank reared fish,” Colin continues. “The Clownfish brood pairs typically lay new batches approximately five days after egg removal or hatching whilst Bangai Cardinals re-lay after three weeks and Dottybacks after about 4-5 days. The egg hatching periods are also species dependent with most Clownfish

batches hatching on day 8, Dottybacks on day 5 and Cardinals on day 14-18.” Peppermint shrimp broodstock are held in a separate system incorporating three 120L, two 54L and six 20L tanks for broodstock and juvenile holding/ growout. This system runs at a turnover of 250%/hr through the tanks with minimal biofiltration. “Our system includes some in-house made foam fractionators with two degassing columns (incorporating a small amount of biofiltration media) and UV-sterilisation through an Emperor Aquatics Lifeguard QL-80. Exchange water for this system is fed through a

Orange Occelaris brood pair with eggs (S. Graham)

Broodstock systems Ornamental fish and cleaner shrimp broodstock are held in a 2,500L recirculation system using trickle biofilters with two Aquamedic Turboflotor twin 5000 foam fractionators and an Emperor Aquatics Lifeguard smart HO 0250240 UV-steriliser. The system includes 20 x 120L and two 250L culture tanks and turnover through these is 100%/hr with a water exchange for the system as a whole of 10%/day. “This system is housed in a temperature and photoperiod controlled room and as such requires no additional heating,” explains Colin. “Standard operating temperature for this system is 27°C with temperatures dropped to 25°C when wintering stock.” The best spawning substrate found for Clownfish is clay pots which can be transferred to hatching tanks once the eggs Autumn 2013 | Austasia Aquaculture 9


Management Metrics Key Management Decisions for BCMI include: • Certification: Gearing up for Environment certification. • Partnering with local commercial and recreational projects. • Use of marine ornamentals and shrimp as training tools, also can sell to the trade. • Two current PhD students from Curtin and UWA are onsite engaged in research into Pink Snapper and Cobia nutrition and health as well as coral larval dynamics. Key performance indicators for Clownfish: • System utilised: recirculation and temperature controlled hatchery systems. • Growth rate (from hatching to market): <4 months (egg to 25mm) • Survival rate: 90+% from juvenile to sale size • Av. stocking density: < 01.5 kg/m3 • Annual harvest: 5,000 (2012 first year of production) • Water use: 5000 L per 1,000 animals produced per year

Whiteline cleaner shrimp broodstock (Dr C. Johnson)







heated header tank (at 26.5°C) which also feeds the flow-through shrimp larval system. Again this system is housed within a temperature controlled room.” Larval production & weaning The larval systems for both shrimp and fish are run on flowthrough systems using temperature controlled header tanks of either clear water (shrimp) or greenwater (fish). Greenwater systems are maintained using a mixture of live algae and algal paste (Proaqua) added to header tanks. Ornamental fish larval production is performed in rectangular 120L tanks and shrimp larvae in upwelling hemispheri-


cal tanks. Water for both these systems is sourced from the common hatchery treated water and both systems are contained in photoperiod and temperature controlled rooms. According to Colin the larval durations

10 Austasia Aquaculture | Autumn 2013

are species specific: “Approximately 8 days for Clownfish, 20 days for Dottybacks and 21 days for Bangai Cardinals with weaning by about 15 days, 25-30 days and 38days respectively. Peppermint shrimp complete larval settle in around 25 days.” During larval development the larvae are fed live feeds. “We use cultured L and S strain rotifers and formulated feeds from Inve Aquaculture; due to due to their ease of harvesting, we exclusively use GSL (Great Salt Lake) Artemia cysts treated with the innovative SEP-Art technology (refer insert box).” “Our rotifer production is either using an Emperor Aquatics rotifer recirc system or batch culture. For enrichment of these live feeds we generally use INVE S-presso.” Colin said that all of their post settlement ornamentals are grown primarily using in-house produced diets. “Our ‘special recipes’ incorporate fresh seafood ingredients, vitamin additives, including Stay-C (Rovimix). To enhance health and colour we add astaxanthin (naturose), canthaxanthin and lucantin yellow or mixed algal derived beta-carotenes from Cognis. (Cognis Australia is the world’s largest producer of algal beta-carotene and carotenoids, branded as Betatene Natural Mixed Carotenoids - refer to feature story in AA Vol 24.2 Autumn ‘10). “The use of these diets has drastically improved both the appearance of broodstock and juveniles particularly in colour intensity as well as their health and the quality of eggs. Further refinement of diets is ongoing. Differing diet formulations are produced for shrimp and fish, juveniles and broodstock. Supplementary feeding with a mixture of frozen commercial aquarium feeds and flakes for ornamental fish is also performed due to their ease of use.” Ongrowing to sale Juvenile peppermint shrimp are housed in the larger tanks in the same system as the broodstock. These are fed on a custom diet similar to that of the fish though


incorporating additional calcium. Moulting occurs approximately monthly and it takes about 5 months to market size (2cm). Cannibalism is the main problem and is combated by the provision of multitudinous structures in the tank consisting predominantly of bunched shadecloth.

Juvenile ornamental fish are housed in a separate 7,000L recirulating system including one 2,700L subdivided raceway with nine 300L compartments, six 300L conical tanks and a 1,000L glass display tank. This system relies on a moving bed biofilter with an Emperor Aquatics Lifeguard Smart HO 0250300-2 UV-steriliser and Aquamedic Turboflotor

Magnetic Artemia Cysts The INVE ( INVE-Aquaculture/Products/) SEP-Art technology cysts contain the same characteristics as the regular Specialty cysts, but have been specially treated with a magnetic coating which allows a unique feature - complete and perfect separation of the nauplii by means of a set of passive

10000 foam fractionator. “This runs at an exchange rate of 30%/ day and a turnover through the tanks of 100%/hr. Temperature is maintained by at 27°C with inline heating on the tank feeding line and a 3kW immersion heater in the sump.” Three juvenile diets incorporating differing formulations are created for black Ocellaris and Clarki, Clowns, for orange Ocellaris, Skunks and Dottybacks, and for Premnas. Cannibalism is only an issue for Dottybacks and no substantial disease

magnets. The magnetic coating

issues have arisen as yet. Growout to mar-

is 100% safe and

ket size of 3cm takes about 4 months for

environmentally friendly.

Clowns and Dottybacks and about 6

• Perfect separation - less than 0,1% of the cysts remain in the water • Environmentally friendly - no use of chemicals • Maximized output - 100%

months for Premnas. “Currently we are selling to retail and wholesale suppliers throughout Australia and we sold approximately 5,000 fish in

From Top: Juvenile Bangai Cardinalfish post settlement (S.Graham) Juvenile growout system being siphoned by Soazig Laumaille (Dr C. Johnson) Ornamental broodstock system at BCMI (Dr C.Johnson)

2012. This year we are planning for continued production of current species at

pure and healthy nauplii

increased levels and increasing our range

• Easy to use - requires a lot

to include several new species and we are

less work and energy than

introducing another 20T broodstock sys-

traditional separation methods.

tem in which blue and Yellow Tangs, Mandarins, and Wrasse are being trialled as development species.”

By Dos O’Sullivan. For more information contact Dr Colin Johnson, Batavia Coast Marine Institute, Willcock Drive Separation Point, Geraldton WA 6530. Tel: (08) 9956-6175, email:

Autumn 2013 | Austasia Aquaculture 11


Gold Coast Marine Aquaculture heads north Located at Woongoolba, half way between Brisbane and the Gold Coast, Gold Coast Marine Aquaculture (GCMA) has been a player in the prawn farming industry for 26 years. In April, 2012, the company headed north and acquired Seafarm’s Killaloe property.


he Killaloe prawn farm was originally

Why buy Mossman?

established in 1985 by Mossman Sugar

One of the main challenges for GCMA

Mill and is located off Packers Creek

has been getting its Black Tiger Prawns

between Mossman and Port Douglas in

(Penaeus monodon) to a marketable size

Far North Queensland. There is 28.7 hec-

for the Christmas market.

tares of water across 25 earthen ponds

“Our problem here, on the Gold Coast, is

aerated by a combination of standard pad-

that we could only guarantee farm product

dle wheels and aire-O2’s at the rate of 20

after Christmas,” says Nick Moore, general

horsepower per hectare.

manager. “We need more time to get them

Farm manager, Jordan Hack, with some of the first crop of domesticated stock through for GCMA at Mossman. These prawns were approximately 55 grams.

12 Austasia Aquaculture | Autumn 2013

to a commercial size of 25 to 30 grams.” This is due to the milder temperatures experienced in south east Queensland. Ponds cannot be stocked earlier than September because it’s too cold and by the time water temperatures are warm enough for growing, it is already October or November. “So when Christmas comes along the prawns are still too small to harvest,” Nick continues. “We have to wait until the middle of January; we start harvesting at the same time as every other farm, we are the same boat as them. “Customers say to me ‘where were you three weeks ago when I needed you? Where were you at Christmas time? A lousy three weeks, surely you could have done it?’ Well it’s not that simple, obviously. We did try.” In fact GCMA tried very hard for two years, on two different properties in south east Queensland, to coax a crop to harvestable size for the Christmas market. But regardless of tactics, the prawns did not grow big enough in time. With its purchase of the Mossman-Port Douglas farm, GCMA can finally supply the Christmas market with fresh product from the north. The Woongoolba farm will supply Easter with fresh product. Frozen product will still be available from the Gold Coast site year round. “When Seafarm came up for sale, we negotiated directly with the owner because we knew that Mossman was the most northern farm in Australia,” Nick explains. “It had the capacity and potential to fill the Christmas gap we had on the Gold Coast. We could start harvesting at Killaloe in November and finish in the middle of January, just when we start


160kg of prawns being removed from the harvest box.

The existing intake pump station which houses a Warman lift pump, 2300L/sec, and a new China pump, 1200L/sec.

From left to right. Pre-existing lunch room, pre-existing workshop (soon to be cleared for extensions to processing), pre-existing processing plant with new awning.

harvesting here. We can now supply fresh product longer than any other prawn farm, other than Seafarm itself. “It also gives a second place to maintain broodstock. There’s a lot of advantages.” It’s not all roses though with some disadvantages to overcome, primarily the challenge of remote management. When GCMA took over the Mossman operation from Seafarm, all the workers were kept on. So, as well as running the farm from a distance, Nick and the GCMA management team have had to get to know a new batch of employees. “We’ve put on a whole group of people that are new to us and unfamiliar with monodon,” Nick says. “They’ve been largely

tied up with Crystal Bay’s Bananas (Feneropenaeus merguiensis). We’ve had to educate them in other management techniques because our farming processes and protocols are different to Bananas.” Stocking the ponds at Mossman For GCMA’s first crop of Tigers at Mossman, all the PLs came from the hatchery at Woongoolba. “We now have a method of flying them up there in one go in an aerated, 1000L, custom-built polypropylene transport bin. We don’t use plastic bags and boxes any more; those days are long gone.” About fifteen per cent of the PLs came

from domesticated broodstock with the remainder from east coast, wild-caught broodstock. There are no plans to establish a hatchery at the Mossman site. Nick believes it to be both too complicated of little commercial advantage. However, a PL nursery might be on the cards. Also highly probable is establishment of a broodstock facility. “Due to environmental parameters and its remote location,” says Nick, “it’s another place we can keep them. If anything ever happened here, we want to make sure we’ve got stocks elsewhere.” Given the use of GCMA domesticated PLs at Mossman this year, the genetic lines Autumn 2013 | Austasia Aquaculture 13


Management Metrics Key Management decisions for GCMA Mossman include: • Selection for domesticated stock to give less stressed, easier to handle prawns with faster growth rates and higher survival • Focus on producing 25 to 30g prawns for the Christmas market. • Supplying fresh product to the Christmas market. • Planning to produce 200 to 300 tonnes/year. • Third party accreditation: HACCP, AQIS Export, SQF200, Coles Supplier. Key Performance Indicators (KPIs) include: • Culture System utilised: saltwater, semi-intensive earthen pond aquaculture, 25 ponds, 28.7ha, average 1.5 ha ponds with paddlewheels and aero2 • Growth rate (from stocking to market): around 4 months (0.1g to 24g) • Survival rate: 70% for this first season, long term target is 75-80%. • Av. Stocking density: < 40/m2 • Annual harvest: 180 tonnes • Production rate: 630kg/1,000m3 • Products: fresh cooked Black Tiger Prawns, 16/20s

Aerial view of GCMA Mossman.

The processing shed with the new portico extension by Sheds Galore. New extension with new provisions for live harvest (air lines, chilled +filtered salt water). Water treatment system (also used in processing shed) consists of Waterco sand filter, FSI micron sock filters, Oxyzone ozone generator, Onga pumps, Oasis water chiller. All assembled in house.

14 Austasia Aquaculture | Autumn 2013

would be continued on from the current stock in ponds. There would be no need to alter husbandry techniques. “There’s really nothing to change. The season just ‘moves forward’ and you take them out. You’re stocking there earlier than you would here, but the time in the water is the same, so it’s just a different time of year.” The first crop GCMA Mossman’s first harvest began in November 2012. Given Nick wasn’t expecting any records, he’s happy that the crop topped 180 tonnes. “It was never going to be a great harvest because the farm was mostly stocked with east coast PLs. They simply just don’t grow as fast. Fortunately, we were able to get domesticated prawns into several ponds and they went remarkably well. Chalk and cheese, absolutely chalk and cheese; they are just so good.” It seems the docility of the domesticated animals allows them to cope well with the farm’s production techniques; they experience far less stress than their wild broodstock-spawned counterparts. This, in turn, means better growth and a better product. The crop at Mossman is being fed exclusively on CP feeds. Whilst food conversion ratios for Mossman are currently 1.7, Nick says the team will be able to do better than that with closer feed consumption monitoring. The thinning harvest technique GCMA uses on its southern farms is also being employed at Mossman. “It is the only method we can use to get the tonnages we require,” Nick explains. “It helps your infrastructure. You don’t put the pressure on the pond... you’re not trying to put 500kg of feed into a pond a day. You’re not putting pressure on your aeration or on your whole water reticulation system. You have a much healthier pond. Keep your bloom stable; keep your prawns happy. That sort of thing. Farming 101; there’s nothing clever in it.” Maybe so, but the protocol is certainly very effective, allowing GCMA to achieve an average of almost 12t/ha last year on


their southern farms (as well as the farm at Woongoolba, GCMA leases a second farm at Tommei). Mossman improvements Since purchasing the Mossman farm, GCMA has undertaken quite a bit of upgrading to the site. At the front entrance had been an old pond. Unusable and very shallow, it was filled in and a new feed shed built on top, replacing the old one that was awkward to access and too close to processing. Now, being at the front gate, feed delivery is easy. The processing facility has also been refreshed including a new water system with ozone sterilisation. Nick says there are, however, no plans to introduce freezing facilities at Mossman. “Mossman is designed to be a fresh product facility only. It’s unlikely that we will be going to frozen product.

Clockwise from top left: Diane Hansen, left, and Tessa Rose sorting prawns at the KM Fish machinery sorting belt and Greer grader. Jordan Hack with freshly cooked and iced prawns ready for transport in 750L Nylex bins. The new 12 metre by 20 metre colourbond feed-shed from Unbeatable Sheds, erected by local contractors. It was built on reclaimed pond land at GCMA’s Mossman farm.

Autumn 2013 | Austasia Aquaculture 15


“We want to tailor our harvesting to the

Prawn fishers and prawn farmers work together!

Christmas period. At the moment, the Christmas period is insatiable in Australia.” Nick laughs: “If we were to grow 250

For many years there has been talk

prawn farming, are now in a very

about the need for prawn farmers

open and very transparent dialogue

and prawn fishers to work together.

with the wild guys. The aim is to join

Many of the problems they face in

together in promoting Australian

the market place, and getting

product, wild and farmed prawns,

product there, are similar: transport

for the very first time.”

costs; packaging costs; advertising

The Australian Prawn Farmers and

costs; food safety; and overseas

the Australian Council of Prawn

competitors to name a few.

Fishers are in discussions and Nick

There is not enough Australian

is very excited about the possible

seafood, wild-caught and farmed,

outcomes. “The whole industry is

produced to satisfy the Australian

growing from where we were.

appetite. Cheap overseas product

We’re not just putting prawns in a

floods the market and profits are

styrene box and bunging them on

down-graded despite having better

the market floor and saying ‘who

quality goods.

wants to buy these?’ The industry is

Nick believes the time is right for an

going to be a true business.”

amalgamated approach by

With a united front and a great

Australian seafood groups to market

marketing campaign, our national

and brand Australian prawns. “The

product could be in for a welcome

prawn farmers of Australia, for the

boost. Watch this space for more

first time in the 25 years I’ve been in


tonnes and it was feasible to harvest the entire crop in a two week period, if that was feasible, that’s what we’d do.” Next year, he anticipates having all ponds stocked with domesticated PLs. The aim will be to supply the Christmas market with 25-30g fresh prawns. “Next year we’ll be much better off. We’ll have the right animals. That’s our plan.” A new gong The team at GCMA are no strangers to winning accolades for their prawns. Previously they have won gold and silver medals at the Sydney Royal Easter Show and have been nominated for the President’s medal. In 2012, further honours awaited. Nominated by his team for the Australian Farmer of the Year, Noel Herbst (owner and founder of GCMA) was chosen as a finalist in the national competition. As part of the proceedings, Noel and his wife, Elizabeth were flown down to Melbourne’s Grand Hyatt for the gala event. Noel represented Queensland against a Wagyu beef producer from Victoria and a beekeeper from Western Australia. “Noel Herbst is a remarkable man,” says Nick. “He’s been farming all his life, prawn farming for 26 years. He’s a hard taskmaster and he’s hard on himself. But he gives as much; he’s all heart and soul. I’ve got the absolute respect for this man.” Noel was runner-up to David Blackmore from Victoria. “Noel said David deserved it,” Nick relates. “When he saw what the fellow had done, he said ‘Wow!’ Noel was very pleased for him.”

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16 Austasia Aquaculture | Autumn 2013

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Seeding Akoya oysters with a round nucleus of Mississippi Pig-toe Mussel. Photo courtesy of Pia Boschetti

The power of passion for pearls A West Australian businesswoman uses her passion for pearls and local artists to create uniquely stunning pieces of jewellery. Her amazing collection complete with the pearl farming story is ‘sold’ through a range of innovative mediums for maximum exposure.


ia Boschetti comes from a WA lobster fishing family. Her love for the sea and its many products has been heightened through her involvement in the familyowned and operated Latitude Pearls based at Geraldton. Originally established in 1998, Pia has been managing this business for over ten years and it continues to grow under her leadership. The clean, warm and nutrient rich waters of the Abrolhos lslands, 70 km off the coast of WA, are perfect for growing several types of pearl oysters. These include the Penguin or Wing-shell (Pteria penguin), Akoya (Pinctada fucata) and Blacklip Pearl (P. margaritifera) Oysters; as a group they

are called AMWING pearl oysters to differentiate them from the Silver or Goldenlipped Pearl Oyster (P. maxima) industry centered around Broome. Another AMWING species is the Shark Bay Pearl Oyster (P. albina). The majority of active AMWING licensees are at the Abrolhos Islands, although several farms are found in Shark Bay, Exmouth Gulf, and the Dampier region. The Leeuwin Current means relatively warm water temperatures year round. Whilst winter water temperatures are usually around 18-20°C, this rises to 22-23°C in autumn or spring and may exceed 28°C in summer at which times the shell grows quickly.

Pia Boschetti with a fine specimen of a cultured pearl oyster that has been opened to show a beautiful pearl. Photo: © Roger Garwood 2013.

Autumn 2013 | Austasia Aquaculture 17


Management Metrics Key Management Decisions for Latitude Pearls include: • Involvement in the industry from the early days with expertise from a long established family fishing business • Engagement of a wide range of local artists and jewellers to design and make the pearl pieces. • Use of the Gallery and other tourist outlets, Facebook, promotional brochures, community events and just open passion to market the pearls. Key performance indicators: • System utilised: surface longlines with hanging net panels for the hatchery sourced shell. • Growth rate (from nucleus seeding to market): 2-3 years • Av. stocking density: Low, maximum of 15 adult shell per panel • Annual Wastes: no supplementary feeding, net extractor of nutrients from the water.

Recently seeded Blacklip pearl oysters are tie clipped into net panels and put back into the sea to hang from surface longlines. Photo courtesy of Pia Boschetti

The AMWING Pearl Producers

Abrolhos, Derek Cropp, Brian Jones and

Association was established in the mid-

Wayne O’Conner developed hatchery and

1990s to represent the interests of these

farming techniques that has allowed the

farms whilst the Pearl Producers

industry to grow [Final Report - 2007/216

Association represents the maxima farm-

– Develop the non-maxima pearl industry

ers. Although eight licences are in oper-

at the Abrolhos Islands (Pinctada

ation at the Abrolhos, the majority of the


production comes from three farms –

Pia’s 3.68ha farm is in the Southern

Latitude Pearls, Chimere Pearls and

group of the Abrolhos Islands. Farming

Abrolhos Pearls.

activities are undertaken off the 10m long

The industry had been hampered by a

aluminium jet boat Miss Pia 2 with its

reliance on wild-caught spat or naturally

Hamilton jet unit powered by a Caterpillar

occurring animals collected from the wild.

engine. “We have land based facilities on

However, during a FRDC-funded project

Basile Island where we reside and con-

on the feasibility of pearl culture in the

duct seeding activities.”

18 Austasia Aquaculture | Autumn 2013

Hatchery Supply Whilst Akoya spat can be easily collected from wild settlement, all three species of pearl oyster cultured at the Abrolhos lslands are produced at the Abrolhos Pearls WA (Chimere Pearls) hatchery – based on floating barge at Coronation Island – operated by owner/ manager Murray Davidson. Murray – along with Alfred (Alf) Woodcock – is a pioneer of pearling at the Abrolhos Islands. The hatchery primarily operates from April till June, spawning selected broodstock lines. The resultant free-swimming larvae are held in 4-tonne round tanks supplied with cultured algae and clean seawater. The correct species and amounts of cultured algae need to be provided regularly to ensure the nutritional requirements of the larvae are satisfied; this allows them to grow quickly. After about 60 days the larvae settle out on 1-3m lengths of Christmas-tree rope which is strung between metal wire panels hung in the tanks. Once the spat are above 1-3mm the panels are transferred to the farms and hung from the longlines. Over the next few months the fast growing spats are picked off the Christmastree rope and placed into small mesh panels. And then for the following 2-3 years, the oysters are routinely cleaned, graded and placed into different sized mesh panels to suit the size of the shell. Pia currently has over 30 surface longlines. Both ends of the 200m longlines are held in place with Stingray anchors and buried in the sand. “We don’t use chains on the moorings we found the chain would create movement and would wear so now only rope is used and attached straight to the anchor. This is a much safer way for the crew to handle the anchors and being located in the sandy areas means we are well away from where the lobsters are.” Each longline is made from 24mm thick polypropylene rope held at surface by30mm black plastic buoys made by Australian Netmakers; second hand buoys are also purchased from other pearl farms.


These brightly painted huts on Basile Island are home to the pearl workers as well as rock lobster fishermen and their families during their fishing season. Photo courtesy of Danielle Prowse.

The main predators are crabs, fox shells (conchs) and hairy slugs (nudibranchs). “Luckily we don’t have much of a predator problem,” Pia says. “Instead our main hassle is spikes in water temperature – up to 29° and down as far as 17° – which causes some shell mortalities.” Fouling is modest and kept in check by cleaning the panels every eight weeks with a gurney water spray. “We found the traditional cleaning machines are too harsh on the shell and if not maintained correctly can cause a lot of downtime. My farm is still quite small scale so a diesel gurney high-pressure water spray works well for my application. They are well priced and you can replace it every couple of years.” Seeding The main seeding time is in May or June; at the same time pearls are harvested from seedings undertaken in previous years. A similar seeding process is used for the different species except for the insertion site of the nucleus (as with the Maxima industry these are made from the shell of the Mississippi Pig-toe Mussel Pleurobema

Lengths of Christmas-tree rope are wound around the net rings and placed in the tanks so the pearl oyster spat can settle on them. Photo courtesy of Pia Boschetti

clava). A piece of mantle tissue, called Saibou, is cut from a selected sacrificial oyster and inserted next to the nucleus. At first all the seeding was undertaken by Japanese technicians. However, Andrew Beer at the local TAFE organised a training course about five years ago. Pia says that the course was very useful as it included shell handling and husbandry techniques too. “It also created better communications between farmers and technicians.”

As Pia prefers to produce larger pearls, she gives the oysters time to grow larger before seeding. For the Akoya a 7mm diameter nucleus is usually used; for the Blacklip 8mm. It takes about 15 months to grow an Akoya pearl but two years for the bigger nucleus in the Blacklip. During this time layers of nacre are laid down over the nucleus to form the cultured pearl. When the pearl is removed, a nucleus of the same size may be reinserted into Autumn 2013 | Austasia Aquaculture 19


the pearl sac – this is called reseeding.

a day and have no rejects. Our only ‘losses’

With reseeding up to three pearls can be

are from the oysters we use for Saibou,

produced in turn. “Due to the improve-

which are the pieces of mantle tissue

ments from the hatchery selective breed-

inserted in with the nucleus.”

ing we are currently able to reseed at least 50% of the shell. Those which can’t be reseeded are used to make Mabe pearls.”

Marketing Given economic downturn in the major

No X-ray checking of the seeding is

international pearl markets (Japan, North

needed as good breeding techniques in

America and Europe), many pearl pro-

the hatchery results in a high success rate

ducers are reducing their businesses to

for seeding. “The shell are all around the

save costs. Not Pia. She is expanding and,

same size, open easily, their gonads are

whilst her business is still small on the

simple to find and generally not deformed,”

international scene, is making great

Pia explains. “This is due to a high level

inroads into local markets by selling beau-

of broodstock selection in the hatchery

tiful jewellery. Her philosophy is simple:

which has led to improvements in pro-

“I give artists the freedom to create amaz-

duction right across our industry.

ing art! We give them a pearl and leave it

“The last two seedings have been our

to them to create some stunning pieces.”

best. We can now seed over 600 shells in

Her biggest competition comes from

Environmental Code of Practice Review The non-maxima pearl industry is a

of the human activities on what are

relatively small, but slowly expanding,

often environmentally sensitive

aquaculture industry which relies on


the maintenance of good water

Whilst proud of its achievements

quality and other environmental

to-date, members of the AMWING

standards for its own success.

Pearl Producers Association

As a net extractor from the marine

recognise the need to keep seeking

waters in which it operates, the non-

higher industrial environmental

maxima pearl industry is one of the

standards. Accordingly, with the

cleanest aquaculture industries, with

Aquaculture Council of WA and the

no supplementary feeding producing

Department of Fisheries they develop-

nutrient-rich effluent. The use of

ed an Environmental Code of Practice

culture methods supporting a low-to-

in 2003. This is currently being

medium density of pearl oysters

reviewed and updated to ensure that

ensures that any additions to the

the environment in which it operates

environment resulting from either the

will be even better protected.

aquaculture or support activities are

The AMWING Pearl Producers

easily assimilated by the

Association hopes, by making such

environment at well below detectable

a tangible commitment to the


environment as represented by this

The non-maxima pearl industry has

Code of Practice, that it will be seen

a responsible attitude towards the

as an example for other marine-

environment in which it operates.

based industries to follow, thereby

Policies and operating standards

ensuring an even greater level of

already in place ensure that rubbish

environmental awareness by all who

and other waste is disposed of

operate within the marine

appropriately, minimising the impact


20 Austasia Aquaculture | Autumn 2013

the Pacific Islands black pearl producers, notably Tahiti. She chooses not to try to compete on volume or price but by producing original jewellery celebrating the natural beauty of local pearls and diamonds. “We use different artists from all around WA to hand craft the pieces. We can also help customers to custom design and create their own unique piece jewellery. Quality craftsmanship by our master jewellers is guaranteed.” But Pia’s formulae is more than just offering beautiful jewellery; she also ‘sells’ the intricate story of each piece, wrapping details of the pearl’s beginnings in the hatchery into information about the seeding process and the 2+year production period, then weaving in titbits about the artist. So the customer gets the full story on how each piece evolved. “Once the customers know the story of how the pearls are produced, how much effort goes into growing them, and understanding the different colours, tints and types then they can see the point of difference we offer. “I am very passionate about my pearls, Pia continues. “My wedding jewellery was made from my own pearls and I want people to see our product and get excited about it. Our local pearl has a huge range of different colour shades; these are just as good as anything else in the world. The diverse range appeals to a wide range of tastes, from younger, fashion style to classic, timeless pieces, across a range of budgets. “We can accommodate varying shades of skin tones as the pearls from the Abrolhos Island region are shades of dark and light silver, with overtones of green and blue, aubergine, gold, bronze and pink. The smooth skins and shimmering colours characterise the Blacklip pearls, whilst the Akoya pearls are generally white or cream with overtones of pink or silver.” Pia uses Penguin and Blacklip Oysters to produce Mabe or half pearls. “Varying shapes are glued to the inside of the shell and nacre then layers over the top. Large in size and full of character, these inspire


jewellers to create unique pendants and rings. “We also source pearls from Broome, Myanmar. Philippines, China, Tahiti and the Cook Islands to provide an amazing range of colours, overtones and shades.” Showcasing the best In 2008 Pia established the Latitude Gallery in Geraldton which has become a showpiece for magnificent jewellery made from Abrolhos Island pearls and Argyle diamonds. She also sells jewellery through tourist shops in regions such as Kalbarri, Yanchep and Bunbury. Prices range from $60 right up to a $24,000 diamond, gold and pearl piece. “We may do small numbers of jewellery at the high end of market, but we have something for every taste. Our sales have increased steadily over the past five years, which is exciting as we are expecting our largest harvest this year.” Pia utilises a wide range of means to get her message to the market, including a beautifully designed webpage, social media through a Facebook page (http://, 20-page full colour booklets which are provided to accommodation, maps of Geraldton with 5% discount vouchers, and involvement in community events. “Last year in March (2012) we worked with the Clean Up Australia committee and Artists for Recycling on the Flotsam & Jetsam project to clean-up islands and bays. We put up $1,000 and a pile of gift vouchers to encourage locals to get involved. We had a 20m crayboat full of rubbish that had washed up at the Abrolhos Islands. On our return the artists collected most of the trash on the boat (the remainder went to landfill). They had a month to make a piece of art resulting in over 100 wonderful items, including a mermaid, paintings, bowls weaved out of old rope and a boat which was made of washed up wood and sea glass. At the opening night of the exhibition in the Gallery we had 300 people and over 50% of these

Above: Akoya shell pegged ready for seeding. Right: Pieces of mantle tissue, called Saibou, are cut from a selected sacrificial oyster and inserted next to the nucleus. Photos courtesy of Pia Boschetti

artworks were sold. This function bought about huge community awareness!” Then there’s an annual social function where Pia’s customers can enjoy a night out at an independent venue. “We take a selection of jewellery art that they can view in a social environment complete with entertainers and singers. A percentage of the night’s proceeds sales is given to the local St John of God Hospital Auxiliary who use the money they raise for extra equipment for the hospital.” Her passion dictates how she runs the Gallery. “It has to be fun for all our team members; they should want to come into work and we work hard to keep it interesting for them. All are local girls and several have been out to the islands and the farm. They know our story and are happy to chat with customers; we want the Gallery to be a great place to visit.” Free tours of the Gallery include a chat about the history about the Abrolhos Islands, an introduction to pearl farms and seeding and pearl harvesting demonstrations. It all takes about 15-20 minutes (plus more time to answer questions) and is followed by a display of pieces of jewellery.

“It’s not about how much money you can make, it is how enjoyable is the experience. When we close a deal on a pearl purchase, we want that customer to be a friend for life. We give Certificates of Authenticity and follow-up with invites to functions, news and other information. Of particular benefit for the husbands or partners is recording a ‘wish list’ for the woman to assist making that ‘special gift’ purchase. By Dos O’Sullivan For more information contact Pia Boschetti, Latitude Pearls, PO Box 77, Geraldton WA 6530. Tel: 08 9964-3470, Mob: 0427 643-470, email: Web: Autumn 2013 | Austasia Aquaculture 21

Improved Fish Cage Net Tensioning


and mitigating seal predation. Though most importantly, the system acts to minimise the risk of failure at every level of the farming infrastructure.

At the Ocean Laboratory at Marintek in Trondheim, Norway - Aqualine has completed simulations and tested cage/net models in order to evaluate the Aqualine Midgard System.

Meticulous co-operation with the global aquaculture industry and oceanographic research players has resulted in the further development of Aqualineâ&#x20AC;&#x2122;s sinker ring concept. The Aqualine Midgard System allows much improved net tensioning, as well as the seamless interaction of cage and net throughout all weather and current conditions, reports Barry McClure General Manager of Aqualine Australasia. The Aqualine Midgard System affords far greater and more even distribution of physical net tensioning that has previously been possible. Seamless integration of the net and cage allows the net to remain fully distended even during times of extreme weather or strong current flows. With the integrated unit consisting of the cage, net and sinker ring moving and 22 Austasia Aquaculture | Autumn 2013

interacting as one, the cage net suffers minimal distortion, deflection and impact to internal cubic stocking capacity â&#x20AC;&#x201C; presenting a significant advantage to farmers. With all farming components functioning in unison, external forces can be more effectively managed. The system also prevents opportunity for the net to make undesired contact with other parts of the cage structure, eliminating potential for net damage and fish escapes while at all times providing absolute maximum tensioning throughout the net. Overall, this new net tensioning system provides significant advantages across a host of operational fronts: providing maximum net capacity; improved water flow throughout the net; safer towing ability when relocating fully stocked cages; and facilitating the use of underwater net cleaning

The initial idea behind Aqualine Midgard System was initially described in a patent from 1999. Aqualine has now reworked this original idea by enhancing and furthering the design concept on the basis of industry needs and requirements of the Norwegian Aquaculture Standard (NS9415). The authority of the Norwegian Aquaculture Standard regulates and certifies all fish farming structures within the Norwegian industry to ensure all is beyond an acceptable standard and absolutely fit for operational purpose.

Model simulations / testing â&#x20AC;&#x201C; November 2012 Together with several global industry players, Aqualine participated in a series of extreme simulation testing at the Marintek Ocean Laboratory, Trondheim Norway in January 2012. Marintek is a world leading oceanographic testing facility, where both waves and current can be simulated simultaneously allowing much greater accuracy in testing than the flume tanks used in the past. Marintek is also the preferred testing institute of the international oil industry, which use its facilities for the assessment of offshore and mid-ocean oil platforms. Following success in this initial testing Aqualine immediately scheduled further assessments at Marintek for November 2012; this time in

partnership with the three largest Norwegian salmon producers – Salmar, Lerøy, and Marine Harvest. Again, a series of very successful assessments were carried out using concept models of the Aqualine Midgard System. The findings of these assessments were very exciting indeed, with the design concept showing massive potential for the way forward. Together with Lerøy Hydrotech, we then gained further insights into operating the Aqualine Midgard System at extreme offshore sites through Aqualine’s participation in the ‘Grip Project’ – an exposed offshore testing site located off the mid-west coast of Norway bordering the open Atlantic Ocean. It was here that the developing concept was tested further using an Aqualine 200m circumference cage through a full season of extreme weather conditions, including sea swells in excess of 11m.

During extreme weather conditions cages and nets need to be professionally designed to provide a safe working environment, structural integrity, a secure growing environment, operational fit for purpose and most importantly provide a cage habitat which maximises fish health and grow out performance.

Aqualine has extensively discussed the new net design concept with leading international net designers competent in the design and production of aquaculture nets, and we have received most valuable input from Salmar, Lerøy, and Marine Harvest. In addition, through this process we have also been able to further fine-tune and simplify the practices involved in operating our cage systems, which will result in considerable gains for industry globally with regard to managing occupational health and safety, efficiency and effectiveness. This further confirms that the Aqualine Midgard System is an unparalleled solution in addressing a range of globally site specific fish farming issues and challenges.

Full-scale field testing The Aqualine Midgard System is currently undergoing full-scale commercial trials courtesy of Salmar, Lerøy, and Marine Harvest. The systems in place are three complete cages, net and tensioning systems utilising Aqualine 157m circumference cages equipped with Aqualine Midgard nets. Work on this project has now been intensified and subject to final verification following the completion of successful commercial field tests, subsequent documentation and certification, the Aqualine Midgard System will be ready for release to the global market around June 2013. For more than three decades, we have cooperated with fish farmers globally in some of the world’s wildest waters. Aqualine have

Aqualine is the global leader in certified advanced cage systems; head office is in Trondheim, Norway and now with a subsidiary office based in Hobart, Tasmania (Aqualine Australasia). Barry McClure is the General Manager of Aqualine Australasia.

constructed and supplied in excess of 6000 fish farming cages and cage systems, and is also a certified supplier of mooring/net analysis, mooring systems and fish farming nets. Aqualine focuses on providing the fish farmer the ’total cage solution’, expertly customised to be fit for purpose and addressing the clients’ specific operational requirements. Aqualine prides itself on its understanding and respect for the ocean and strives to build safe and robust products for the fish farming industry.

Contact details: Aqualine Australasia Barry McClure (General Manager) Mobile: +61 0417 19 1234 Email: Website: Autumn 2013 | Austasia Aquaculture 23


Abalone farmer settles down to steady harvests Abalone farming in Victoria has been through some tough times. From its pioneering days in the 1980s, to the herpes outbreak of more recent years and now the profit-eating rise of the Australian dollar, it’s been a steep learning curve.

Two year old abalone – note the growth rings. This photo is of black lip abalone. Future breeders will be selected from this stock.


ne of the pioneers has been Ocean Wave Seafoods Pty Ltd down at Lara Beach on the entrance to the Geelong Arm of Victoria’s Port Phillip Bay. Founded in 1998, the farm currently turns off 35 tonnes a year from its simple yet effective flow through system. By crossing blacklip abalone with the more reclusive greenlip species, Ocean Wave produces its own hybrid ‘tiger’ juveniles. This cross occurs naturally in the wild under certain conditions, when the breeding trigger of the two species overlaps. Growers have found that the heterosis gives an advantage on the farm as well as producing an attractive line for marketing purposes. Water is pumped ashore through the tanks at the rate of 250L/sec when the farm is running at full capacity. A 3m x 3m x 3m box covered by 50mm diamond netting at the intake keeps puffer fish, jellyfish and seaweed out of the farm. A bank of eight sand filters ensures the nursery water is free of particulate matter. Generally they’re flushed daily but, when the loadings of suspended organics are high, flushing can be carried out as often as every two hours. Port Phillip Bay has a narrow opening to Bass Straight and tidal exchange is limited. Due to the Bay’s shallow overall depth – it covers 195,000ha but only averages 13m in depth – there’s an unusually wide temperature span for such a 24 Austasia Aquaculture | Autumn 2013

large body of water, ranging from 23°24°C at the peak of summer to drops to 10°C in the middle of winter. Spawning & early development Spawners are held at 17°C in the hatchery from July and by October their gonads are fully conditioned. They’re given a sudden temperature shock of 20°C after

which the temperature is dropped back to 17oC. At the same time the water is given an ozone boost to induce ovulation and spawning. Whilst the spawners are induced in the same water, they are held separately in 20L tanks. Eggs are fertilized manually – they’re removed and mixed with the milt from a selected green-lipped male. Although Farm Manager Joel Gilby points


out that they don’t have a breeding program as such, they do have a family combination with which they’re satisfied for the time being. Approximately 5,000,000 larvae are spawned each season. By encouraging natural attrition, after six days on the yolk sack, around one million spat will settle in the nursery on sheets that have been inoculated with the micro algae Ulvella lens. They’re then fed a diet of different benthic diatom species but primarily Navicula. The sheets are 300 x 600 mm and ideally stocked at up to 40 spat per sheet. More than 25,000 sheets are run in the nursery. Grading in the nursery in March culls another 30%, leaving 700,000 to be stocked in the fifty 3m x 1m weaning tanks. Water temperature have by this time dropped down to 19°C. Once they have settled, the spat are weaned onto an artificial diet and ongrown in the weaning tanks for another six months before being graded a second time, at which

The individual larval rearing tanks (LRTs).

Abalone ready for the market.

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Autumn 2013 | Austasia Aquaculture 25


point the best performing 50% will be moved to the growout. The remaining 50% are left in the weaning tanks for the summer.

Clockwise from top left: Two year old abalone – note the growth rings. Joel inspects the condition of a sheet of newly settled juveniles. The bank of sand filters that keeps the nursery water pristine.

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26 Austasia Aquaculture | Autumn 2013

Growout Growout is carried out in 40,000L shallow – concrete tanks with a depth of 0.5 m and a diameter of 10M. Ocean Wave use 59 of these tanks. Growout times have been improved dramatically over the years. The early timetable was 4-4.5 years. Improvements in husbandry methods, based on experience and observation, have made an impact as have selective breeding programs. While dealing with a wild animal suggests immediate chances for improvement from careful selection, there’s still the need for performance comparisons and stock management. One of the biggest improvements has come from improved feeds. A Cooperative Research Centre (CRC) program between industry and FRDC-funded nutritionists has not only improved the efficiency of the available rations but also dramatically reduced the cost. (FRDC = Fisheries Research & Development Corporation) The farm uses use Adam and Amos feed from South Australia. Feed conversion efficiency is a healthy is 1.2 -1.3. “We could probably do a little better, but we don’t underfeed. We’ve found it better to keep the growth rates going rather than skimp on feed to save a few dollars,” Joel explains. At weaning, the abalone are fed a starter diet of 35% crude protein and 3-5% crude fat until they reach 25mm (12 months old). After that they’re fed a ration of 30% crude protein with a crude fat value of 4%. Water temperatures can be a problem, especially in these times of extreme weather events. At the peak of the summer, water temperatures can get as high as 23-24°C. Joel reduces feeding during these times, maximises water flow and adds extra aeration to keep the dissolved oxygen levels as close to saturation as possible. After their second year, 20% of the aba-


lone have grown to 50 g (65mm). So far the farm hasn’t had any major disease outbreaks and managed to dodge the herpes virus outbreak that took such a toll on some farms in Bass Strait. Marketing Ocean Wave’s marketing pitch is its ability to supply clients throughout the year. It uses three marketing grades – 18-20 per kg (50g -55g approx), 14-16 per kg (60-70g approx) and, at certain times of the year, 10-12 per kg (85-100g approx). The most popular size is the 18 -20. To maintain a regular weekly supply, Joel commences harvesting after two years. The stock of that spawning cohort is then harvested over the next 14 months. “Everything is off the farm in around three years. We hold a bit back for the Christmas rush but we don’t carry the larger/older stock through another summer. We’ve found the larger stock stress a bit in the warmer water”, he says. Prices have eased back from the heady levels of the early days when $50/kg was the accepted farm gate price. The high Australian dollar and international competition has forced down the benchmark export price, but the improved technology built on experience and research has also reduced the cost of production. Better feed prices and efficiency has also greatly helped to lower costs. Fortunately, the major inefficiencies have now been corrected by trial and error and are behind them, Joel says. Whilst margins aren’t exorbitant, they’re healthy, and with the farm’s output is more predictable, the markets have settled down too. The future – and just reward for their tenacity and hard work - looks promising for Ocean Wave Seafoods. By John Mosig Joel Gilby can be contacted by email on

Clockwise from top: One of the 59 growout tanks at Ocean Wave Seafoods. The control panel for the hatchery. Note the inline heater on the left hand side and the 3 ozone generators on the right The broodstock conditioning tanks at Ocean Wave Seafoods.

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Aquaculture caught in the headlights with disease Prawn farming can be a volatile business particularly if your farm succumbs to disease issues. Diseases are a current and present danger with the costs currently estimated at USD6 billion annually. One of 100 ponds in operation at PT. SEAFER, Indonesia.

Pond Manager inspects the stock.


veryone starts in business with a

thoroughly, took lots of advice and

dream. Harry Sudarwo was no differ-

engaged with other partners to create PT.

ent to many other Indonesians when he

SEAFER General Foods. They secured

decided to move from the wild catch

sufficient land to establish over 500

industry – where his family had been

ponds, concentrated their efforts on one

working for many years – into prawn

species, Black Tiger Prawns (Penaeus mon-


odon) and had done their homework on

The family knew the business of prawns and Harry investigated aquaculture very 28 Austasia Aquaculture | Autumn 2013

marketing. It was not long before they had created

a quality reputation with all of their buyers – particularly in France – and, with this encouragement, they built a processing facility within their farm area. This was going to make them vertically integrated as a business and they were starting to live the dream. Little did they know that just around the corner danger was lurking. White Spot Sydnrome Baculovirus complex (WSSV) came calling at their farm and soon after the dream turned into a nightmare. When disease strikes no one is ever truly ready for it. Even those companies with strong risk management processes never really think this could happen to them. One day all is well and the next you are dealing with a crisis and trying to protect what you can. In towns like Kendal, Central Java, Indonesia, where PT.SEAFER, operated the impact cuts deep. As the company expanded the town had flourished as most of the employees were local. Conversely, as staff were laid off, this impacted the whole region. Harry Sudarwo is not one to dwell too much on the past. But you can see in his face how much it hurts. He and hs partners took the losses on the chin and put the farm into mothballs. It would be understandable if they walked away and never came back but Harry and his group are a hardy lot. After a few years of soul searching Harry and his team were itching to do something. The emergence of Penaeus vannamei in Asia made them think about restarting the business. Clearly lessons have been learned. Farm biosecurity is now much stronger and overall the business is looking to has-


ten slowly. After 18 months they have reestablished 100 of the ponds and are planning to expand into another 100 in the next year. The processing plant has not been re-opened; the priority is to get the cash flow in good shape by simply concentrating on farming activities. Meanwhile a new disease is heading their way and the need for diligence in all activities in and around the farm is essential.

Feast for a king awaits in the Board Room.

Prawn diseases Over the last few years the major diseases that have attacked prawns have been: • Yellow Head Virus (YHV) • Infectious Hypodermal and Hemalopoietic Necrosis Virus (IHHNV) • Infectious Micro-necrosis Virus (IMNV) • White Spot Sydnrome Baculovirus complex (WSSV) • White Feces • Bamboo Shaped Disease • Acute Hepatopancreatic Necrosis Syndrome (EMS/AHPNS). All of them have impacted in some way, some worse than others, but the latest disease – known simply as Early Mortality Sydrome (EMS) – has many people concerned because it has not been fully diagnosed despite the mighty efforts of the world’s experts. The full title for EMS is Early Mortality Syndrome/Acute Hepatopancreatic Necrosis Syndrome and the tell tale signs relate to significant atrophy of the hepatopancreas (HP), often pale/yellow or white within the HP with black spots or streaks occassionally visible. The HP does not squash easily between the thumb and forefinger. As the name suggests EMS affects

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Journeying through the 500 pond farm at Kendal in central Java.

Boiled Vannemai Prawns.

prawns in the first 10 to 40 days after stocking. Mortality rate is 40 to 90% no matter what the species and it has been documented that survivors display slow growth. Falling production As can be seen from the table of production trends (supplied by GAA) for shrimp (prawn), the drop in production in countries like China, Malaysia, Thailand and Vietnam is all due to disease, particularly EMS. Also of great interest is the 30 Austasia Aquaculture | Autumn 2013

predominance of P.vannemai; 80% of the global harvest is of this one species. The GOAL Conference held in Bangkok in November 2012 featured detailed presentations and discussions regarding EMS. George Chamberlain brought together experts Prof. Donald Lightner (University of Arizona) and Dr. Tim Fiegel (National Science and Technology Development Agency) along with FAO specialist, Rohanna Subsinghe and NACA’s Chadag Mohan in a panel discussion to highlight the enormity of the problem. The cost of prawn diseases is now put at $US6 billion annually. All such diseases are supposed to be reported to World Organisation for Animal Health (OIE – website In the Asia-Pacific region the Network of Aquaculture Centres in Asia-Pacific (NACA – www. is responsible for gathering the data and reporting to OIE. Although much of the reporting is not done as efficiently as it should be, NACA try their

best to comply and issue a quarterly report. The OIE produce a report every six months. According to the rules laid down by OIE countries farmers should report to the relevant authority within 24 hours if having experienced any of the following: • an exotic disease; • a sudden increase in prevailance of known endemic disease; • an unknown disease and/or disease events of epidemiological significance to trading partners. However, NACA highlighted that national coordination in many countries is poor and communication and information transfer, crucial is times of crisis, may not be sufficiently effective. Whilst the best solution would be for each country to have a national level task force and an Aquatic Animal Health emergency fund, Dr Mohan pointed out that many countries have been too slow to acknowledge the problem and were not complying with the OIE emergency notification requirements. Of course one of the fears all farmers face is that their operation maybe closed down by the authorities. If no compensation mechanisms are established, that’s a strong incentive not to report a disease. Another disincentive is the emerging risk that suppliers in countries with reportable diseases may their stock rejected due to biosecurity procedures in importing countries. It’s no surprise then that NACA noted that those countries with compensation mechanisms have much better recognition of disease emergencies. The conclusions reached during the GOAL conference were that all parties needed to understand the consequences of diseases and that health management should be a shared responsibility with primary industry, the full supply chain and government investing to build resources and capacity so that aquatic animal disease emergencies were better managed, if not prevented.


Pond and Farm Managers having discussion with guests including Dr Agung Sudaryono.



Compared to 2010


Forecast for 2012




Production Growth





Likely drop





- 5% to -15%



- 4% (Diseases)


- 20%





+ 10%













- 2%





- 20% (WSSV)












Likely drop






NOTE: 80% OF GLOBAL AQUACULTURE PRODUCTION IS P. vannamei. vs. 43% in 2004 15%

P. monodon

5% Macrobrachium/Other species

Note: More than 60 % of Chinese production is consumed locally. Annual growth rate for period 2010-2012 = 1.3%


Af Q fo u rd a ab li le ty Pr ice s

Australian situation In a 2012 report ‘Australia’s Disease Status and Risk Pathways’ by Dr Matt Landos and Dr Christine Huynh from Future Fisheries Veterinary Service Pty Ltd, the diseases that have been detected in Australia are: • Gill-associated virus (GAV) • Monodon Baculovirus (MBV)[Spherical baculovirus] • Hepatopancreatic parvovirus (HPV) =PmergDNV densovirus • Spawner isolated mortality virus (SMV) • Mourilyan Virus (MOV) • White tail disease – Macrobrachium rossenbergi nodavirus (MrNV). All farmers in Australia should note that the Aquatic Animal Health Program (AAHP) leads and coordinates the national management of aquatic animal health for: • finfish (including barramundi, native fish, salmonids and tuna) • crustacea (including prawns, lobsters and yabbies) • molluscs (including abalone, edible oysters, mussels and pearl oysters). The AAHP supports the development of AQUAPLAN - Australia’s National Strategic Plan for Aquatic Animal Health and coordinates the national response to aquatic animal disease emergencies, based on AQUAVETPLAN. Australia’s commitment to international agencies and agreements for aquatic animal health is also coordinated and managed by the AAHP. A list of current reportable diseases can be seen at http://www. reporting/reportable-diseases. In Australia DAFF Biosecurity develops new policy, usually through an Import Risk Analysis (IRA), and also reviews existing quarantine policy on imports. The ‘Australia’s Disease Status and Risk Pathways’ report highlights this and these other good management reasons why Australia may be the ‘lucky country’ in respect of disease issues as : • AQIS import-IRA which includes testing of imported green prawns • Remote location from farms in Asia



Autumn 2013 | Austasia Aquaculture 31


• No live prawn imports • Vertical farm integration – limited PL and equipment sharing • High quality feeds and pond management. Biosecurity plans are essential and should be totally adhered to as this is the best defence to any disease. Dr Ngan Taw, a recognised expert in prawn farming, currently working for Blue Archipelago in Malaysia, gave some of these recommendations on biosecurity actions that should be taken by every farm during his excellent presentation at the Indonesian Aquaculture Conference in Semarang in November 2012: • Biosecurity starts from the pond construction. All risks should be eliminated and every precaution taken. This should cover everything from using a reservoir module system to the water treatment systems, development of standard operating procedures, ensuring bird scare lines and crab fences are in place and only stocking the ponds

with Specific Pathogen Free (SPF) post larvae (PL). It is important to remember that high density stocking likely means stress and that opens the door to disease. Control workers’ movements – farm/ farm, module/module, row/row. Eliminate unnecessary handling/touching of stock with ideally only one person responsible for handling product. Staff must be trained, not only about their tasks but to understand the overall biosecurity plan. Worker numbers need to be minimised and organised into teams working on stocking, sampling, harvesting, etc. All equipment in operation – eg. PWWAs (process water and waste water treatment), water pumps, siphons, etc. must be kept clean and that is best done by using chemicals and sun drying to disinfect – this must be done on screen nets, cast nets, etc. A focus on overall environmental cleanliness within the grounds including car

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dips, ponds, water, housing, etc. • Control of all human traffic into the grounds – guests, workers, technicians, management personnel, etc. Security and vigilence is essential. • Certification should be considered as this brings a discipline to all daily routines and ensures systems are audited to enable continuous improvement. • Prevention with third party verification is a major goal for all farms as this brings many advantages. The final words on prawn farming and the issues that have to be faced go to a legend in the industry, Dr. Chingchai Lohawatanakul, President and Vice Chairman of Charoen Pokphand Foods Public Co., Ltd., who, when presenting at GOAL, said: “Shrimp business is like marriage: The outsiders want to get in, and the insiders want to get out.” By Roy Palmer.

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Looking from what is left of Blue Lagoon Oysters towards the virtually untouched shed of Cremorne Oysters

Oyster farmers to rise from the ashes Like millions of Australians watching the evening TV news on Friday 4th January, I was taken aback by the enormity and fury of uncontrollable bushfires sweeping down through the Tasman Peninsular.


the Camerons well – our friendship and

Tom Gray – singed and burnt as they raced

business relationship goes back many

for shelter – 1500 never making it to


safety .

So of course I was on the phone as soon

Tom’s family sought refuge in waters of

as I could, but it was only the following

the nearby bay, while Tom (unsuccess-

day that I could talk to Ian, the company

fully) endeavoured to prevent the flames

founder and grandfather of Ben, who runs

from destroying a tractor and trailer

the operation now.

loaded with hundreds of new oyster grow-

nowing well the beautiful and his-

Ian’s own home at Murdonna came

toric small communities of Dunalley

within only meters of being destroyed by

out Aquatrays. Luckily though he did have his home saved by a water-bombing helicopter.

and nearby Boomer Bay, the decimation

the fast moving inferno (see accompany-

of over one hundred homes and busi-

ing story by his neighbour, Carla Falzari).

I was shown by Ray Schwenke and Sue

nesses was particularly devastating.

Amazingly, the company’s Dunalley

Madden of Blue Lagoon Oysters, the mol-

I closely watched footage of the ruin of Dunalley’s bakery, all the while not know-

premises were also spared. I was later to see photographs of the

ten remains of a large aluminum oyster boat in amongst their factory devastation (aluminium melts at 660°C).

ing the fate of the adjoining premises (just

black, wildly swirling flame-laden clouds,

10 paces away) of Cameron of Tasmania

hundreds of meters high, enveloping the

Gradually I was able to establish con-

– its office, laboratory, oyster hatchery and

area. And photographs too of the com-

tact with friends and business associates,

nursery. Cameron of Tasmania is a vital

pletely blackened wool of hundreds of

including Ray Murphy of Oysters

cog in Tasmania’s oyster harvest. I know

sheep belonging to oyster farmer/grazier

Tasmania and obtain an overview of indiAutumn 2013 | Austasia Aquaculture 33


Assistance for oyster farmers Following the Tasmanian bushfire, the growers in the south-east are being helped by both the Tasmanian oyster industry and the Federal and State governments to get back in business. Each operator will be provided financial assistance via the Tasmanian Bushfires clean-up fund. Enterprises that have sustained direct fire damage are eligible to apply for assistance up to $25,000. The aluminium oyster boat belonging to Ray Schwenke and Sue Madden (Blue Lagoon Oysters) melted from heat exceeding 660°C.

vidual involvement and effect. A number were business customers of TTPPlastics to whom we had supplied oyster farming equipment (Aquatrays, Aquapurse etc) for a great number of years and had become personal friends. A visit to the area was not possible for many days because of strict restrictions (even on residents who had fled from the fiery onslaught), understandably imposed by involved Authorities. (Police, Fire Brigade etc.). When eventually able to visit, I was enormously impressed with the resilience, overall optimism, the “we’ll be back” atti-

tude shown by so many who were greatly affected. I was to hear many very ‘close shaves’. Naturally many were sad, but then some were quite humorous. For example, the fire had roared down the forest on a nearby hill onto the property of Justin Goc of Barilla Bay Oysters in Dunalley. It destroyed a large stack of plastic oyster baskets before approaching his house, burning all the surrounding garden shrubs and reaching his front door just as the water bomber helicopter arrived and extinguished the blaze. Meanwhile, Justin (having already sent his wife and family to Hobart) sought ref-

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Several businesses have already obtained new baskets and trays and have been actively putting these together and getting oysters out in the water. A Sorell/Tasman Economic Reference Group is being established and will include a representative from the local oyster growers fraternity. Ray Murphy, Oysters Tasmania

uge under rocks in the water one hundred meters away. When safe, he returned to the house to find the only internal damage came from an intruder … a panicstricken wallaby that had hopped in through a broken window. Visiting this devastation, it’s hard to understand how some homes and properties escaped damage, whilst those around turned to ash. But witnessing what I did and speaking at length to many who were involved, I know for sure that Dunalley, Boomer Bay, Murdonna and the surrounding areas – supported by their fellow Taswegians – will rebuild their lives and businesses. I returned home several days later, very much effected by the stoicism and determination of those who have suffered enormously in so many ways. For this reason alone I look forward to returning and witnessing a resurgence in this wonderful part of Tasmania. By Reg Breakwell


A survivor’s tale

Carla took refuge in the water as did many residents of the area. It’s easy to see why.

It’s a surreal experience to be told by police that it is now time either to evacuate or to stay and defend your home from an out-of-control bushfire, knowing that by doing so you could be putting your life at risk.


he morning I had spent enjoying the sun at the beach with both my Mum

The fire left many scenes of total devastation in its wake.

and Dad, a nice surprise because Dad rarely ever came out on the kayaks. After such a wonderful beginning how could it go so wrong? It was just after lunch that we decided that the smoke over the hill was far too close for comfort. Dad rushed off to put our vehicles away and Mum led our five ponies, three donkeys and a 42yo horse into the paddock closest to home. I collected a few bits and pieces from the house then we put the dogs and parrot into our old 4WD, which Dad drove onto the rocks with the back wheels in the water. At around 5 o’clock our neighbours Autumn 2013 | Austasia Aquaculture 35


The fire rapidly advancing on properties around Carla’s house at Murdunna.

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36 Austasia Aquaculture | Autumn 2013

Barbara and Ian Cameron of Cameron of Tasmania decided the water was now the safest option. I waited by myself in the 4WD for half an hour before realising that a family friend from Dunalley was alone around the corner of the beach. I helped her carry her valuables across the rocks to the 4WD. We waited another half hour before her husband came down the bank. Soon after that the fire came tearing down upon us and we were in the water with our noses touching the surface trying to find air and all along not knowing if anyone else was alive. At some point while checking the dogs were ok, I managed to collect a minor burn on my face showing just how hot it was. After a traumatic – and very long – 20 minutes or so my Mum turned up through the water. She was in tears, believing that by leaving the animals for her own safety she had committed them to death. She disappeared not long after that up over the hill and into blackness and thick smoke. We followed. Happily all the animals were all still there looking at us and, by another miracle, the fire had spared our house. My recollections of that night are a bit blurry. I do recall carrying heavy buckets all through the back yard and across paddocks. I remember too dunking my t-shirt in the wishing well because it was so hot and later on lying on the ground near the shed watching our 42 tonnes of firewood burn away. Saturday morning was so very different to the previous one. Instead of kayaking we walked up the road to see who still had homes and who didn’t. By Carla Falzari Carla and her family are very grateful for all the supplies that have been donated and to the Emergency services especially the Fire Brigade, Police, SES and Red Cross.


Pedigree prawns For hundreds of years, farmers have been undertaking in genetic improvement through the selection of the best animals to breed for the characteristics they desire in their herds. Seafarm, Australia’s oldest and largest prawn farm, has demonstrated that it is possible to do the same with prawns.


n his talk at the Australian Prawn Farmers Association and Australian Barramundi Farmers Association conference in early August 2012, Dr Wayne Knibb, from the University of the Sunshine Coast (USC), spoke of the research into genetics and pedigree that he and his team have been undertaking with Seafarm’s domesticated Feneropenaeus merguiensis (Banana Prawns). They believe they can achieve the same genetic improvement in the aquaculture of prawns that herd breeders have been achieving for hundreds of years. Existing Broodstock Seafarm has been maintaining pure bloodlines of Banana prawns over the last 11 years (see AA vol.26 no.3). This gave Wayne a solid foundation for his research. “Our first mission was to understand if past breeding practices had affected the genetic diversity of the bloodlines,” says Wayne. “This can happen for aquacultured species, especially prawns, because of their fecundity and challenge to identify individual offspring and parents. You might think you are getting a broad selection of broodstock by keeping thousands to breed , but because a single mother can produce offspring numbering in the tens of thousands, there may be little genetic diversity amongst them. “If you’ve been working with sheep you wouldn’t have run into this problem. If you’ve got a thousand lambs, you’ve probably going to take the genetic representation of a thousand ewes. “Often the genetic programs used in aquaculture have been designed by sheep or cattle breeders who haven’t run into this particular issue of extremely high fecundity.” The breeding program at Seafarm involved selecting broodstock for size in order to breed a bigger, faster growing prawn with increasing uniformity of size and passivity when handled (which indicates decreased susceptibility to stressors). Over the course of fifteen generations, Seafarm had significantly increased the size of their domesticated Banana Prawns compared to those bred from wild caught spawners (Figure 1). After controlling factors such as stocking density, feed amount and type, days in production and other factors, analysis showed that the pure bred domesticated prawns were 23% larger than their wild counterparts. To determine the level of genetic variability remaining in the farmed stocks, genetic testing of wild females was undertaken. It was found there were about 20 different mitochondrial haplotypes – a set of labels within a small stretch of DNA indicating the closeness of the family ties – in the wild caught popula-

tion. Genetic testing of the bloodlines at Seafarm found there had been some contraction of diversity of haplotypes since the breeding program commenced. One option to improve genetic diversity was to re-introduce wild stocks but this would result in a loss of genetic improvements. “It’s doubtful that you could run a profitable Banana Prawn business without the genetically improved line,” says Wayne. “We need to keep the pure lines but we need to keep them in a sustainable way. This means without loss of diversity.

Figure 1: The gains in weight by selecting for size in domesticated prawns (the adjusted body weight is determined by correcting for age and density etc.). Compare the weight of the wild broodstock product to the pure line domesticated product which is 23% larger.

Figure 3: Comparing weight gains across wild-spawned progeny, purebred progeny and crossbred progeny (the adjustments are for age, density, etc.).

Autumn 2013 | Austasia Aquaculture 37


Using the microarray technology to test for light versus dark colour in prawns. Note the fluorescing microdots, the greater their intensity the higher the gene product.

Dr Wayne Knibb delivering talk at the Australian Prawn Farmers Association and Australian Barramundi Farmers Association 2012 Conference. Photo by Tracey McKean

The graph shows the cost (expressed in time worked to pay for product) of a chicken in 1940 compared to the cost of a chicken today. It also shows where Australian prawns currently sit. Genetic manipulation through breeding practices developed the chicken from a small, leggy bird affordable only occasionally into a plump, full-breasted beast within everyone’s budget. Using similar techniques genetics could make prawns more profitable for farmers and more affordable for the consumer.

38 Austasia Aquaculture | Autumn 2013

“The good news is that if we look across the haplotypes of each of those pure lines and we recombine the many lines into one line, and then compare the diversity of the reconstituted bloodlines, it’s not that dissimilar to the wild.” (Figure 2). “The really interesting thing that occurred when the pure lines were crossbred was that there appeared to be another increase in weight (Figure 3). So not only was the original weight increase from wild spawn preserved but cross-breeding may have further improved weight gains. However, some caution needs to be taken as the data for the crossbred line are only available for a year or so; these trends need to be solid for several years of data. “It seems as though the data are supporting each other,” says Wayne. “The performance data actually on the farm is consistent with the genetic information we are uncovering from our forensic DNA technology.” Commercial traits The second objective in this project was to determine the genetic basis for commercial traits. Can the genetic heritabilities and correlations for commercially important traits be estimated? “This is more than an academic or scientific exercise,” explains Wayne, “Because if we know the genetic basis of the traits we can design the most efficient ways to make breeding selections, meaning the most efficient way to make commercial progress.” This is how good research can improve the bottom line for farmers. Finding which desirable characteristics are genetic and which are environmentally-determined would enable the farmer to selectively breed to enhance the genetic ones and possibly change practices to improve the environmental cues. “There are two key pieces of information we need to design an efficient project. One is heritability, which is the measure of how strongly the genes are influencing the traits. Our selection procedure would emphasize the trait with the greatest genetic component. The second is the genetic correlations and the strength of those correlations.” Such correlations can be negative. For example, genetic traits can be linked – if you get one, you get the other. Or they can be antagonistic – if you have one, you lose the other. For example, if colour and size have a negative genetic correlation and the farmer selected breeders for their nice red colour, he would also be selecting to lose size. Tracing genetics Wayne believes that genetics is not a complicated business. “We want to understand if genes are controlling a trait. If we just pick mums up out of a pond, we are left with uncertainty as to how much of their differences are due to environment and how much is genetic. We also have to look at their daughters and sons. “It’s the same story with cattle. If you have a dairy bull that you think would be a good breeder, you can’t actually assess his ability to produce milk just by looking at him because he’s a bull! However,


The team at USC: (left to right) Rob Lamont, Paul Whatmore, Nicole Ertl, Dan Powell & Angelico Madaro. Absent: – Wayne Knibb, Abigail Elizur, Anna Kuballa, Jane Quinn & Nguyen Nguyen.

we can assess his genes if we look at one of his daughters. “But a single daughter’s performance is a poor indication of his breeding value for milk as she may have had sickness as a calf or a particularly good diet. What if we looked at a thousand of his daughters? This is possible in dairy breeding. All of a sudden we have a very accurate estimate of his genetic capacity to breed for milk production.” He argues it is no different with prawns. “The problem arises in knowing which spawner produced which progeny, so that we can track the heritability of traits. Knowing the pedigree is necessary to ranking the relative performance of individual prawns.” Forensic DNA technologies have been developed that allow

this to be done; indeed USC has developed a DNA microsatellite test specifically for Banana Prawns. Wayne and his team now have a test they can use to establish the genetic profile of an individual – a ‘barcode’. This ‘barcode’ can be used to trace each animal’s pedigree. “With Seafarm we have developed very advanced ways of picking an animal out of a pond and telling who the mum and dad were,” Wayne says. The USC team is about to publish a paper on estimating genetic values for prawns. This will allow the industry to formulate the best way to improve their selection process; this translates into more genetic improvement which, in turn, translates into benefit for the bottom line. Finding commercial genes The third objective in the project was to identify commercial genes and their markers. “Why is it beneficial to find genetic markers for desirable traits?” asks Wayne. “Why not do it the old-fashioned way and selectively breed for them? The short answer is expense, time and risk.” Some traits are difficult to measure; for example to measure prawn taste is an expensive and prolonged procedure. A panel of tasters has to be assembled, terms have to be agreed upon and standardised. Even so, subjectivity may still creep in. “If we can benchmark genes which contribute to these traits” says Wayne, “We can then conduct animal selection based on the genes themselves.”

Autumn 2013 | Austasia Aquaculture 39


DNA microarrays (see picture) are being used to investigate the gene expression of Seafarm’s Banana Prawns. Each slide can have 20,000 spots of different DNA sequences per prawn. Two prawns can be compared for a trait on a slide, for example, a light coloured prawn and a dark coloured prawn. Wayne and his team have found that there is a gene which leads to a prawn to being more colourful when it is cooked. This is a world first discovery: colour is heritable. They are now investigating this gene more thoroughly in their labs at USC. “We feel that we have some genetic leads to commercial traits like colour. It’s still provisional but we’re very encouraged by our results.” There is hope that this technology can be also used to look for genes for resistance to diseases such as HPV and this work can then serve as a model for identifying disease resistance in other species such as Black Tiger Prawns (Penaeus monodon).

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Down on the farm A peripheral objective of the project with Seafarm was to find out how genetic programs can be worked on the farm. Frequently, research is done in a university lab or government facility with the results being most true for that locality. The USC group have developed the tools to do the research on-site because they can identify the families of given untagged individuals; this is more likely to deliver a more relevant result to the farmer. The results for the first part of the project (to see if past and present practices lead to significant inbreeding) are in. Pedigrees are now able to be developed and the problems can be ameliorated. The science has been investigated and delivered a favourable outcome for industry. Far more speculative is the quest to find commercial genes. Wayne has been encouraged by the discovery of genes that impact colour but says: “It is still at the research stage and certainly way before any industry adoption. The nature of

research is that we often don’t know where it will take us. So, we are very happy to have found some pointers.” Through the genetic assay technique, an incidental discovery was made: banana prawns are monogamous. Whilst many species will mate with multiple partners to produce one batch of offspring, female prawns appear to only mate with one male within each moult cycle and for each breeding episode. This has made the work a lot easier for the team by greatly simplifying the calculations. When asked why has it taken so long for bloodlines in prawns to be investigated? Wayne replies “Logistics and the lack of current DNA technology would have to be the reason. Without the new DNA tags (microsatellites) and genetic sampling, each generation of broodstock would have to be kept in separate aquaria to be sure of their pedigree. This would involve a huge infrastructure investment on the part of the farmer. “We are coming from a different perspective,” says Wayne. “Let’s not move the mountain to us; we’ll go to the mountain. We’ll bring a kit that allows us to deal with genetic issues in a serious and responsible way without having to set up an expensive dedicated facility with lots of staff. Technology has developed in such a way that we can deploy genetic capacity onsite.” The work was supported by Seafarm, The Australian Seafood Cooperative Research Centre, The Fisheries Research and Development Corporation, The University of the Sunshine Coast and the Australian Prawn Farmers Association. By Tracey McKean All images adapted from Dr. Wayne Knibb’s PowerPoint lecture, except where indicated. For more information contact Associate Professor Wayne Knibb, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD, 4558. Tel: 07 5430-2831, email:


Purging effects on yabbies (Cherax albidus):

does purging produce a superior product?

Summary Since the 1980s growers have promoted ‘purged’ yabbies (Cherax albidus) as superior to ‘wildcatch’ (unpurged) yabbies. Purging is a process where yabbies are starved before sale. Although most yabby consumers are familiar with ‘hindgut content’ in the tail meat, studies overseas have identified content removal may make yabbies more appealing. Victorian yabby growers commissioned this research to determine purging effects on yabbies using different methods over time. This is in response to the economic burden involved in purging and anecdotal reports that purging may not be effective at removing hindgut content. NSW producers sell 42 tonnes of unpurged yabbies annually, with 29 tonnes grown in South Australia. In Western Australia purging in the 44 tonne industry is voluntary for between 0.5 – 2hrs. The 1.6 tonne Victoria, industry, in contrast, must purge for 48hrs, in clean, solid water, in a shed, under the PrimeSafe food safety licencing system. The question is whether Victorian regulations lead to superior yabbies. The experiment compared the baseline ‘control’ yabby hindgut content (without purging) to that retained under three purging systems a: ‘bath’ (solid water system, in a shed in clean, clear bore water at 19.2°C); b: ‘mist’ (yabby shower in a shed in clean, clear bore water at 19.2°C) and c: ‘sock’ (in clean, turbid solid water, in a dam at 21.2°C). Observations included physical condition, hindgut content and activity. Many of the yabbies purged for 12 hours or greater in shed treatments had shell discolouration (pink), unlike sock purged yabbies. Discolouration is associated with lower market prices. Yabbies removed from the mist system demon-

Figure 1: Solid water ‘bath’ purging in shed. Bore water flow rate 10L/minute

Figure 2: Shower ‘mist’ purging in shed. Bore water flow rate 5L/minute

Autumn 2013 | Austasia Aquaculture 41


Background Yabbies for human consumption Yabbies (Cherax albidus) are a native, endemic species to south western Victorian waterways and were translocated to WA in 1930 (C. Lawrence, 1998). Yabbies have been harvested for consumption for thousands of years. They are drought tolerant and live on aquatic plants, macro-invertebrates, detritus and material washed into the waterway (C. S. Lawrence & Jones, 2002). Yabbies are a popular food and, like other seafood, domestic consumption peaks in December with prices peaking the week prior to Christmas. Yabbies, which are typically cooked (a critical control point for food safety) soon after catching, are a low risk food product (Fabris, 2004; Food Standards Australia and New Zealand, 2005 p225). Yabbies have performed exemplary in national residue studies and have low chemical accumulation results (Fabris, 2004; State Chemistry Laboratory, 2003). This makes yabby growing appealing to many farmers wishing to diversify. In 1990 there were 100 yabby farms in Victoria, with 24 in commercial production (Commonwealth of Australia 1993). The industry rapidly grew after this time, with wives and children using yabby sales as supplementary farm income, In Victoria an industry high production was achieved in 2001 of 31 tonnes (Department of Primary Industries, 2003).

Figure 3: Solid water ‘sock’ purging (in dam)

Figure 4: Hindguts ready for analysis after being weighted.

strated heightened aggression compared to the solid water systems, with aggression linked to claw and yabby losses. Unpurged yabbies contained, on average, 69% hindgut content. The greatest purging effect was found in 48hrs mist with 32% hindgut content remaining. The PrimeSafe approved purging method of 48hr bath (shed) reduced hindgut content on average to 45%, a 38% net result. A large natural variation was observed, with some yabbies still retaining up to 100% hindgut content after 48hrs. Equivalence to the 42 Austasia Aquaculture | Autumn 2013

48hr bath was achieved at 6hrs in the mist system and 24hrs in the bath and sock. Based on effects to physical appearance, mortality, stress and aggression, purging was not found to be an effective method for removing hindgut content, in any system. An equal result can be achieved by removing the central tail fin and hindgut, within 15 seconds per yabby. If desired by customers, purging for a minimum time was supported by these findings, being 6 hours in a mist system or 24 hours in a solid water system.

Purging yabbies In the 1980s a marketing campaign began to promote yabbies harvested in aquaculture as superior to ‘wildcatch’ yabbies. The main differentiation point was ‘purging’. Purging is the process where yabbies are starved prior to sale, with the aim of reducing hindgut content. This is based on research in the United States which encouraged growers to reduce hindgut content (‘poo’) in tails, which was thought to be unappealing to new customers not used to eating freshwater crayfish, including restaurant patrons (Lawson


& Drapcho, 1989; Lawson, Lalla, & Romarie, 1990; McClain, 2000). No Australian research has been found which supports this view. The United States (USA) research was conducted on the related red swamp crawfish (Procambarus clarkia). Purging was introduced in many American operations due to the added benefit of providing cheaper storage than cool rooms typically used (Lawson & Drapcho, 1989). The USA studies stated that purging crawfish is not the same as ‘depuration’ of shellfish which improves food safety outcomes in high risk foods which are consumed raw (Lawson & Drapcho, 1989; Lawson, Lalla, & Romarie, 1990). Two studies found purging to be effective in removing 100% of hindgut contents on visual inspection within 30-40 hours (Lawson & Drapcho, 1989; Lawson et al., 1990); a subsequent much larger study, which included dissection, showed that only approximately 80% of hindgut content was removed after 48hrs (McClain, 2000). Significant crawfish losses were found as time increased, and this main study concluded that purging should be limited to 12 hours (McClain, 2000). While a voluntary practice, yabby purging, has been used throughout the industry since the 1990s. Many farmers use holding cages or ‘socks’ in dams, while other farmers have invested in shed based purging systems. In sheds, a ‘mist’ system is preferred by growers over solid ‘bath’ water due to greater shed capacity and reduced risks from power failure (Mosig, 1998; Department of Fisheries; C. Lawrence, 1998). There are no reported food safety incidents resulting from consuming purged, or unpurged yabbies in Australia (Fabris, 2004; Food Standards Australia and New Zealand, 2005 Victorian Regulations A major change in yabby farming regulation occurred in Victoria in 2004 with live yabbies intended for human consumption becoming subject to PrimeSafe regulation and mandatory purging. PrimeSafe require a minimum of 48hrs

purging to remove hindgut contents and

Australia voluntary purging for 0.5 – 2hrs

muddy flavours (PrimeSafe, 2011).

sustains a 44 tonne industry (Department

Yabbies must be purged in clean water in

of Primary Industries). The annual com-

a dedicated shed and mist purging is not

mercial yabby catch in Victoria has now

an approved method. PrimeSafe require

dramatically dropped to around 1.6

the water source to be different from that

tonnes per annum (including non-human

the yabbies are grown in. Although the

consumption), with fewer than three pro-

Victorian Yabby Growers Manual

ducers remaining. This is in contrast to

(Victorian Yabby Growers Association of

the 1500 tonnes of unpurged ‘wildcatch’

Victoria, 2001) states yabbies must be

yabbies consumed in the state. Victorian

purged in clean water, there is no science

producers have an added pressure

available showing any food safety or food

whereby many of the yabbies from other

quality effects of purged versus unpurged

states are being transported to Victoria


for human consumption, without food safety licences required. Thus it remains

Industry status

that most Victorian customers eat

The NSW commercial yabby catch cur-

unpurged yabbies.

rently sits at 42 tonnes per annum and

The requirement imposed by PrimeSafe

South Australia at 29 tonnes, both states

is reported by Victorian growers as a major

do not require purging. In Western





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(Domaschenz, Trevor 2012). This is due to the length of time (48hrs) the location (in a shed) the method (solid water) of purging required with no known science to support this minimum standard. Impetus for research Anecdotal evidence suggests that full hindgut removal in cherax albidus is not achieved within 48hrs. There are no scientific studies that suggest that yabby hindguts are carriers of pathogenic bacteria, and thus there is no specific benefit of purging on food safety. Further, pathogenic bacteria would be killed through the normal practice of cooking (Fabris, 2004; Food Standards Australia and New Zealand, 2005 p225). The industry finds itself in a position where there is no scientific evidence to prove or disprove the need for purging, let alone the length or technique that would have an effect on either for food safety or food quality. This has led to this self-funded research. The Victorian yabby industry supported study to determine the effect of purging on yabby hindgut content and to explore comparable methods and times for purging yabbies to that required by PrimeSafe. This includes using a: ‘bath’ (solid water system, in a shed, in clean water); b: ‘mist’ (yabby shower in a shed in clean water) and c: ‘sock’ (in solid water, in a dam).

Observations were made of physical condition, hindgut content and activity. Hindguts were visually analysed for ‘percentage length content’, and ‘average batch percentage length content ’. The study is exploratory as there is no current Australian standard methodology. Method Australian Research There is no Australian standard methodology that identifies a method of assessing yabby hindgut content, nor a study into effects of different purging methods. PrimeSafe anecdotally indicated that a visual inspection of 10 yabbies trialled in different batches could be an appropriate methodology for establishing purging effects and parity, based on their review of a 1989 study in America on purging effects on red swamp crawfish. International Research Research in USA indicated different methods were used in assessing purging effects on red swamp crawfish. As these species are related to the Australian yabby, these methods could provide some insight. Lawson and Drapcho (1989) completed a study to compare solid water and mist system purging systems. A visual inspection was used to estimate if the gut was completely, nearly completely, or partially

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evacuated in 20 yabbies from each treatment, high flow through solid water, low flow through solid water and a spray treatment, purged for 48hrs. The water flow rates were 7.6L/m, 3.8 and 7.66l/m. All crawfish were caught from a single pond with a (small) average size of 16.7g. Lawson et al. (1990) conducted further research on mist purging. Four flow rates were used with four repeats of each condition up to 40hrs. A spray rate of 3.6L/ minute was effective with stocking density below 24.4kg/m3 and bore water 19°C- and 20°C. Crawfish were completely purged after 30-40hrs. Ten randomly selected crawfish were analysed. McClain (2000) analysed purging effects in mist and solid water systems after 12, 24, 36 and 48 hours using dry weight analysis as a percentage of overall tail weight on crawfish. McClain conducted 17 trials and found up to 80% hindgut evacuation. His detailed investigation revealed limitations in purging effectiveness that was not identified in earlier research. Technique adopted A rapid assessment methodology, based on the three USA studies was adopted. This incorporated visual assessments with linear analysis of the hindgut performed using a ruler. Yabbies were collected from a dam currently approved by PrimeSafe for food production. Traps were baited on 30th November and yabbies collected on the morning of 1st December. Yabbies may have fed during capture. Ten yabbies were randomly selected for each trial, sized between 48-80g, individually weighed, sexed and coded. The tray of yabbies was then photographed, and placed into the purging treatment with time on entry recorded. Two control samples were used to establish baseline hindgut contents. These were compared against three purging systems a: ‘bath’ (solid water system, in a shed, in clean bore water at 19.6°C – figure 1); b: ‘mist’ (yabby shower in a shed in clean bore water at 19.6°C – figure 2) and c: ‘sock’ (in solid water, in a dam at 21.2°C


Natural variation between the randomly

The average results at 24hrs achieved

selected unpurged samples was high (fig-

parity with the 48hr bath effect of 43%

ure 5). Yabbies were found to contain

hindgut content in both the mist and sock

between 100% hindgut content and 8%.

purging systems (both 42%). Bath purg-

The average result for the two samples

ing at 24hrs retained 45% hindgut con-

was 69% hindgut content. This result was

tent which, accepting the level of individ-

used as the control figure in further

ual variation from the control point,


remains comparable to the 48hr bath purging result. Mist purging at 12hrs

Analysis of purging effectiveness by

(50%) and 6hrs (51%) were slightly

technique over time

higher content rates than 24hrs or 48hrs.

Twelve trials were completed using the three purging methods over time. The

48hr solid water purging – minimum

results are shown in Figure 6.

Victorian PrimeSafe standard.

Across all purging methods there was

PrimeSafe require Victorian yabby

a general decline in hindgut content over

growers to use a 48hr solid water (bath)

time, the only exception being 2hr (bath)

shed based purging system. For this rea-

or 2.5hrs (mist and sock) treatments (fig-

son the 48hr results were explored in

ure 6). The greatest purging result was

more detail and other results compared

found for mist purging 48hrs which

for parity. PrimeSafe have indicated they

recorded 32% hindgut content. Purging

would only consider alternate purging systems, where their provide an equiva-

water systems - the bath and in the sock.

lent result to the 48hr bath.

Time 0 (n1) 100 50 0 1










% Hindgut Content

was comparable over time in both solid

% Hindgut Content

– figure3). In total 15 trays were analysed. As trial densities (650grams) were well below typical commercial loading (5000g) one tray was filled at commercial stocking rate to monitor mortality in the mist system after 48 hrs. On removal, yabbies were photographed, and their physical appearance and activity noted, prior to being frozen. The yabbies were frozen for 2.5hrs then photographed and analysed. The hindgut was accessed by separating the raw yabby tail from the body (twisting action), then holding the central tail fin and pulling. This process took between 10-15 seconds per yabby (2 minutes per batch). The tailfin was retained with the hindgut for analysis, to reduce potential losses through dissection. The hindguts were labelled, photographed then re-frozen (figure 4). Analysis was completed through visual inspection and measurement of hindguts for each yabby. One millimetre measurement intervals were used in establishing hindgut content. This allowed for the percentage of hindgut content to be calculated on an individual and batch basis. The total length of hindgut per batch was assessed and relative hindgut content for each trial batch compared. Weight was initially recorded, but found to be an unreliable predictor of hindgut content. Due to the high level of variation in hindgut evacuation between individuals statistical analysis was kept to a minimum.

Time 0 (n2) 100 50 0 1

Yabby Number










Yabby Number

Figure 5: Baseline individual yabby percentage hindgut with poo. 100 90

Purging method used bath mist


% Hindgut Content

Results The ‘control’ sample hindgut contents (two samples n1 and n2) were compared to the three purging systems over time. Times selected for analysis were 2hrs, 2.5hrs, 24hrs and 48hrs for all three systems. The mist system included two additional trials at 6hrs and 12hrs.


sock 60 50 40 30 20

Control sample hindgut content – no purging Two control trials were conducted with no purging. The average results of these were used to determine the baseline (‘control’) hindgut content percentage.

10 0 0






Purging time (hours) Figure 6: Purging effects over time by treatment

Autumn 2013 | Austasia Aquaculture 45

50 0 1








9 10

Mist 6hrs 100 50 0 1


Yabby Number







9 10

Yabby Number

% Hindgut Content

Bath 48hrs 100

% Hindgut Content

% Hindgut Content


Mist 12hrs 100 50 0 1








9 10

Yabby Number

Figure 7: Bath purging results after 48hrs

Figure 8: Mist purging individual yabby hindgut content retention results by percentage for 6hrs and 12hrs.

Although figure 6 revealed an average purge result of 43% retained hindgut content for the 48hr bath, figure 7 shows that results for individual yabbies remained highly variable. After 48hrs purging one yabby retained 100% hindgut content and another 0%. Equivalent results based on average hindgut content to the bath system was achieved in all systems by 24hrs (figure 6).


Mist purging compared to the benchmark. Mist purging is the most common shed based system used by industry, therefore further analysis of the mist purging results at 6hrs and 12hrs purging were undertaken to compare individual variability as well as the average result. The mist system 6hrs had three yabbies with 0% hindgut content, comparable with the 48hr bath purging (figure 7) which had two yabbies with no content. In the 12hrs trial, six yabbies had less than 43% hindgut content, while the bath purging system had only five yabbies below this result (figure 7). These results show that while the average result was slightly higher in the 6hr and 12hr mist purged yabbies, the effect on individual yabbies was highly comparable to the 48hr bath purging system. Yabby condition and activity Assessment of yabby activity found that the mist purged yabbies were more aggressive on removal than either the sock or bath systems (Figure 9). Many yabbies had claws open and were moving actively around the trays, some with claws clamped on other yabbies. 46 Austasia Aquaculture | Autumn 2013

Many yabbies in the 24hr and 48hr mist

Hindgut removal The results indicated that purging does

and bath systems were discoloured with

not remove 100% hindgut content within

pink highlights on their underbellies, tail

48 hours. The greatest effect was found

fins, back of head and sides (Figure 10).

in mist purging for 48hrs where 32%

The discolouration was still obvious in

remained, representing 46% change from

tails after even after dissection.

the baseline of 69%. In the bath system

Mortality and other losses

representing a 38% effective change. Less

the process has changed content to 43%, The commercial density stocked tray in

effect from purging has been found in

the mist system recorded two yabby fatal-

cherax albidus yabbies than for previous

ities. No claw loss in any system was

studies on red claw crawfish in which


found between 80% removal (McClain, 2000), to 100% removal (Lawson &


Drapcho, 1989; Lawson et al., 1990).

Natural Variability

Cherax albidus may be more resistant to

A significant finding in this research

purging effects than crawfish.

was the variability in purging effects

As full evacuation is not achieved dur-

between yabbies. There was not a pro-

ing purging, this potentially unappealing

duction like movement of hindgut con-

aspect of yabbies is not addressed. A far

tent over time between samples. In the

more efficient and effective way to remove

48hr bath purging system one yabby

hindgut content was used during this

retained the full hindgut contents

experiment, whereby the hindgut is man-

throughout the hindgut length, whereas

ually removed from the tail, including the

another had no content remaining.

contents within. This process took less

Although the individual hindgut content

than 15 seconds per yabby or two min-

could be highly variable, over time there

utes per batch.

was an increase in the number of yabbies which showed a cleared hindgut across

Other purging effects

all purging methods. The increase in


hindgut content over time, evident in

The negative effects of purging were

some samples may be due to either nat-

found from 12hrs onward with discolour-

ural variation or the movement of diges-

ation of yabbies in both shed based purg-

tive products through the animal. McClain

ing systems. Yabbies were found to be

(2000) also found variability within tri-

tinged pink on the underbelly, back of

als. Of 11 trials conducted, on one occa-

head and sides. Yabby shell discoloura-

sion peak purging occurred at 12hrs and

tion is known to affect marketability. This

on four occasions at 36hrs rather than

effect was not reported in USA studies on

48hrs as would have expected, had hind-

crawfish (Lawson & Drapcho, 1989;

gut evacuation been linear over time.

Lawson et al., 1990; McClain, 2000).


Aggression A negative effect of mist purging was increased aggression in all samples, this was not reported in the USA on crawfish, although reference to cannibalism was made ( McClain, 2000). Yabbies were found with claws open and in some instances the claws were clamped onto other yabbies, potentially causing shell damage. Increased aggression is known to contribute to claw loss or shell damage, resulting in an undesirable product for the restaurant trade. Mortality A ‘commercial’ density prawn tray was kept under the mist system for 48hours (this was not undertaken in the bath due to volume restrictions) and found that there were two yabby losses. Yabby losses and condition loss in purged yabbies is consistent with findings internationally (Lawson & Drapcho, 1989; Lawson et al., 1990; McClain, 2000). Yabby death represents a unrealised commercial product as dead are yabbies unfit for human consumption. Other effects summary These results show that there are a number of negative effects due to purging that reduce yabby condition, yabby numbers and marketability. Growers need to maintain maximum financial outcomes for their business and are encouraged to calculate the positive outcomes of marketing purged yabbies against these other effects. The USA studies recommend a minimum purging time of 12hrs based on similar negative effects (Lawson & Drapcho, 1989; Lawson et al., 1990; McClain, 2000). Preferred options for growers The greatest purging effect was found with 48hrs mist purging, although almost 1/3 of the hindgut still contained content. As purging changed hindgut content from 69% to 42%, it would not be appropriate to market the yabbies as ’fully purged’. The results indicate that a mist system will

Figure 9: Aggressive mist purged yabbies (claws open)

Figure 10: Yabby showing clear signs of ‘pinking’ behaviour

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achieve comparable results within 6hrs (50% and 3 clean hindguts) and solid water within 24hrs (42%), to the results found from 48hr purging. Consistent with USA studies which indicated a preference for a 12 hour maximum purging time due to potential losses and yabby effects (McClain, 2000), this study supports using least input method of achieving an equivalent result for purging effect. For those wishing to purge for marketing purposes, sock purging in dams is the lowest input method of purging, where regulatory burden does not exclude this option. Sock purging achieved comparable results to those found in the shed purging systems from 24hrs. Growers should calculate individual production costs and review negative purging effects when making a marketing decision for their operation. As 100% hindgut evacuation was not achieved in this study, there remains no evidence that demonstrates that purged yabbies are superior to unpurged yabbies being sold across Australia. Implications for Victorian Growers Benchmark condition for PrimeSafe compliance PrimeSafe require a stricter regime for purging than the rest of Australia. The benchmark condition of purged yabbies is defined by PrimeSafe as the condition the yabbies were observed after 48hrs purging in a bath (in a shed, in clean water). In this study the average hindgut content after 48hrs was 43%. The visual (and linear) analysis of individual yabbies revealed four of the ten yabbies had close to complete evacuation at this time. Parity with the benchmark condition The 6hr mist purging system achieved comparable hindgut content based on individual yabby results with the PrimeSafe benchmark condition. The 24hr bath and mist purging system also produced a comparable result to the 48hr bath purging. Due to the risks of purging 48 Austasia Aquaculture | Autumn 2013

including death, cannibalism, claw loss or colour change identified in this and previous trials (McClain, 2000) growers should use a cautious approach to purging and where possible use these shortened, parity times. Both mist and solid water systems can be used with confidence and meet current PrimeSafe Licencing Requirements for an equivalent result to a 48hr shed, solid water, purge. Moving forward Solid water purging for 48hrs reduces hindgut content by 38%, and was shown to have no effect on some animals. Purging for 48hrs does not achieve 100% hindgut evacuation, thus this process does not achieve the desired outcome of full clearance. These results indicate that the regulatory regime in Victoria is more onerous on growers than is necessary. Future options and research Further investigation is needed to determine whether or not the partial evacuation of hindgut through purging increases the marketability of yabbies. Research is also needed to clarify the role of each step in yabby processing to remove potential contaminants and maximise yabby health and survivability, to determine less onerous options for growers. A review of growers guides and regulatory regimes is encouraged in light of full hindgut evacuation not being achieved when purging yabbies for up to 48hrs. This may assist with increasing Victoria’s commercial yabby production in line with other states. By Toni Domaschenz and Jeremy Draper Toni Domaschenz: (BSc Aquatic Science, Grad Dip. Sci. Comm.), Principal Consultant, Streets & Creeks Consulting. Contact: Jeremy Draper: (BApp.Sc. (Environmental Health), Grad.Cert. Environmental Health Risk Assessment, Diploma Quality Auditing, Food Safety Auditor (NFSA 4)), Principal Consultant, JCBD Consulting. Contact:

BIBLIOGRAPHY Australian Freshwater Yabby Growers of Victoria (2001) Victorian Yabby Producers Manual (2001) (pp.33). Austrlian Freshwater Yabby Growers of Victoria. Commonwealth of Australia (1993). Australian Fisheries Resources. eds. Kailola, Williams, Steward, Reichelt, Mc.Nee, Grieve (pp. 422): Commonwealth of Australia. Department of Fisheries. Farming yabbies (pp. 7): Government of Western Australia. Department of Primary Industries. Table 1 Comparison of Regulatory Requirements for yabby producers supplying for human consumption (pp. 1). Department of Primary Industries. (2003). Aquaculture Information Bulletin: Department of Primary Industries. Domaschenz, Trevor (2012). re: the Inquiry into the Impact of food safety regulation on farm and other businesses: Please find following a submission by myself on behalf of Victoria’s Yabby Industry. (pp. 43). Fabris, G. (2004). Aquaculture Notes: New tool to assist the clean green production of yabbies (pp. 2): Department of Primary Industries. Food Standards Australia and New Zealand. (2005). Final assessment report: Proposal P265: Production & processing standard for seafood (pp. 334). Lawrence, C. (1998). Yabbies. In K. W. Hyde (Ed.), The new rural industries : a handbook for farmers and investors (pp. 147-152). Canberra, Australia: Rural Industries Research & Development Corporation. Lawrence, C. S., & Jones, C. (2002). Cherax. In D. M. Holdich (Ed.), Biology of freshwater crayfish (pp. 635 - 669). Oxford ; Carlton, Vic.: Blackwell Science. Lawson, T. B., & Drapcho, C. M. (1989). A comparison of three crawfish purging treatments. Aquacultural Engineering, 8(5), 339-347. doi: http://dx.doi. org/10.1016/0144-8609(89)90040-X Lawson, T. B., Lalla, H., & Romarie, R. P. (1990). Purging crawfish in a water spray system. Journal of Shellfish Research, 9(2), 383-387. McClain, W. R. (2000). Assessment of depuration system and duration on gut evacuation rate and mortality of red swamp crawfish. Aquaculture, 186 (3–4), 267-278. doi: http:// Mosig, J. (1998). The Australian yabby farmer (2nd ed.). Collingwood, Vic.: Landlinks Press. PrimeSafe. (2011). Licencing requirements applicable to seafood businesses harbesting yabbies for human consumption (pp. 1-4). State Chemistry Laboratory. (2003). Yabby Risk Assessment: Appendix 5 Results of chemical analysis for pesticides in yabby samples from selected dams.


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