Fisheries Research Report Series - NSW Department of ... · Fisheries Research Report Series: ... Culture of the Australian Flat Oyster ... SWOT ANALYSIS FOR DEVELOPMENT OF FLAT OYSTER

Fisheries ResearchReport Series:

Proceedings of the Workshop held on 3 March 2000at the Sydney Fish Markets: Problems

of Producing and Marketing the Flat OysterOstrea angasi in NSW

edited by

Mike Heasman and Ian Lyall

June 2000

ISSN 1442-0147

6

Fisheries Research Report SeriesThis series presents scientific and technical information on general fisheries research andthe documents in the series are intended to be progress reports on ongoing investigations.Titles in this series may be cited as publications, with the correct citation on the frontcover and the page following the cover.

Fisheries Research in New South WalesResearch at NSW Fisheries is based at a number of locations, including Cronulla, PortStephens, Narrandera and Grafton.

Studies cover Commercial fisheries, Recreational fisheries and Aquaculture. Research isalso completed for conservation issues in coastal and riverine areas.

The major role of research conducted by NSW Fisheries is to provide information uponwhich relevant Fisheries Management policies and strategies are developed, monitored andassessed in terms of the Department’s obligations under the NSW Fisheries ManagementAct, 1994.

Published by:NSW Fisheries Research InstituteJune 2000ISSN: 1442-0147

Enquiries:NSW Fisheries Research InstitutePO Box 21, Cronulla NSW 2230

Telephone (02) 9527 8411 Facsimile (02) 9527 8576

Fisheries ResearchReport Series:

Proceedings of the Workshop held on 3 March2000 at the Sydney Fish Markets: Problemsof Producing and Marketing the Flat Oyster

Ostrea angasi in NSW

edited by


Plate of farmed flat oysters (photo courtesy Neil Hickman)

June 2000

ISSN 1442-0147

6

Flat Oyster Workshop, by Heasman & Lyall

Fisheries Research Report Series: No. 6 i

TABLE OF CONTENTS

1. EXECUTIVE SUMMARY AND RECOMMENDATIONS .............................................................. 1

2. AIMS OF THE WORKSHOP .............................................................................................................. 4

3. OPENING ADDRESS

BILL RUTLEDGE .................................................................................................................................... 5

4. GENERAL INTRODUCTION AND BACKGROUND ON FLAT OYSTERS AND THEIRCULTURE

NEIL HICKMAN, ROB ADLARD, MIKE HEASMAN* AND IAN LYALL................................................... 7

5. PILOT COMMERCIAL HATCHERY AND NURSERY REARING OF FLAT OYSTERS INNSW 1996-1999

MIKE HEASMAN AND LINDSAY GOARD................................................................................................ 8

6. PRACTICAL EXPERIENCE GAINED FROM TRIAL COMMERCIAL FARMING OF FLATOYSTERS IN NSW

MIKE HEASMAN AND IAN LYALL ....................................................................................................... 16

7. NOVEL TECHNOLOGIES FOR THE REDUCTION OF BIOFOULING IN SHELLFISHAQUACULTURE

SOPHIA MCCLOY AND ROCKY DE NYS .............................................................................................. 19

8. BONAMIA SPP DISEASE OF FLAT OYSTERS

ROBERT ADLARD................................................................................................................................. 24

9. REVIEW OF FLAT OYSTER AQUACULTURE RESEARCH IN VICTORIA

NEIL HICKMAN.................................................................................................................................... 28

9.1. Culture of the Australian Flat Oyster (Ostrea angasi) in Victoria (Hickman N.J. and O’MeleyC.M. 1988a)................................................................................................................................. 28

9.2. Hatchery and Nursery Production. (Hickman N.J. and O’Meley C.M. 1988b)............................. 299.3. Development of Commercial Field and On-growing Systems for Production of the Flat Oyster

(Ostrea angasi) in Open Waters. (Reilly, D. and Hickman, N.J. 1994)....................................... 309.4. Storage and Shelf life of the Australian Native Flat Oyster (Ostrea angasi) (Mantzaris, L.,

Hickman N.J., and Grossel, G.W., 1991)..................................................................................... 34

10. MARKETING SCOPE FOR FLAT OYSTERS IN NSW, INTERSTATE AND OVERSEAS

NICK RUELLO, (RUELLO AND ASSOCIATES), MARTIN PALMER (MARTIN PALMER SEAFOODS),MARK EATHER (JOLLY ROGER EXPORTS) ........................................................................................ 48

11. SWOT ANALYSIS FOR DEVELOPMENT OF FLAT OYSTER OSTREA ANGASI FARMINGIN NSW

MIKE HEASMAN AND IAN LYALL ....................................................................................................... 51

12. DELEGATES AND ABSENTEE CONTRIBUTORS......................................................................... 55


ii Fisheries Research Report Series: No. 6

ACKNOWLEDGEMENTS

We wish to make special mention of David Maidment for his dogged determination infostering diversification of the NSW oyster industry into flat oysters. We are especiallyindebted to Neil Hickman. The value of Neil’s entertaining and informative summation ofinnovative flat oyster nursery, farming and post-harvest handling protocols developed byMAFRI in Victoria between 1986 and 1992, cannot be overstated. We applaud the courageand financial commitment of all eleven oyster farmers who over the past 3 years havepioneered the farming of flat oysters in this state. We also thank the other guest speakers,Robert Adlard, Sophia McCloy, Ray Tynan and Laurie Lardner. We gratefullyacknowledge Lindsay Goard, John Smith, Nick Ruello, Martin Palmer, Mark Eather, ChrisBoyton, Geoff Allan, John Nell and Helena Heasman for their individual contributions tothe workshop and to preparation of these proceedings. We also commend other workshopparticipants all of whom contributed to a very lively and useful discussion of practicalexperience gained from the past three years of pragmatic trial farming and marketing of flatoysters in NSW.


Fisheries Research Report Series: No. 6 1

1. EXECUTIVE SUMMARY AND RECOMMENDATIONS

Hatchery, nursery, farming and post-harvest handling techniques used to produce flatoysters in central and southern NSW over the past three years and in Port Phillip Bay,Victoria between 1986 and 1992, were reviewed in some detail.

Practical experience to date is that there are few if any serious technical barriers to reliableproduction of seed juveniles. Flat oysters can be grown to optimum domestic andEuropean export market size of 70 mm (80 g) in one and a half to two years in inter-tidaltray culture, and perhaps less in floating trays as demonstrated at Bermagui or suspendeddeep water culture as demonstrated in Port Philip Bay. Optimum growing height for inter-tidal tray culture on existing leases is indicatively 25 to 30 cm below that of Sydney rockoysters. Flat oysters grown this way have shown low susceptibility to mud worm and bio-fouling especially if air dried in the shade for two to three days each month during the highbio-fouling season from late Spring (November) to late Autumn (May).

By far the greatest difficulties encountered to date by the eleven NSW oyster growersinvolved in trial farming of flat oysters has been post harvest and marketing problems.Foremost of these has been very short (two to three days) shelf life when handled the sameway as Sydney rock oysters, highly variable meat quality between consignments andpresence of gravid black-sick and grey-sick brooders among consignments as far apart asJune and February. Major factors known to reduce flesh quality are farming protocols,especially; growing height, excessive stocking densities and bio-fouling occlusion of mesh,in tray and basket reared oysters and seasonal factors especially spawning and lowtemperatures.

Bonamiasis was clearly exposed as the greatest potential risk to the long-term sustainabilityof flat oyster farming and to the export potential of this species. However off-bottomculture and harvesting of flat oysters prior to first spawning were identified as possibleways to minimise these risks. Likewise, surveys to identify disease-free production areas,certification of these areas and adoption of farming techniques involving quality assuranceprograms to safeguard the health of consumers were identified as possible ways ofovercoming barriers to export.

Although flat oysters will need to compete against locally produced and imported rockoysters they do have a competitive edge in appearance and greater apparent potential forexport. The most important marketing message was the need for growers (not marketers)to collectively develop and ensure orderly marketing of flat oysters that are safe forconsumers, are of a standard size and uniform good flesh quality and go by a singleuniversally recognised and attractive name such as Angasi or Belon. The next mostimportant factor is the adoption of long shelf life packing and chilled storage methodsalready developed and documented by the Marine and Freshwater Research Institute(MAFRI) in Victoria.


2 Fisheries Research Report Series: No. 6

Recommendations

The following recommendations are based on those provided by individual speakers. Theyalso embrace issues raised in the SWOT analysis and opinions expressed in an opendiscussion at the workshop on the following industry development issues:

! Need of a simple farming guide and development of extension services.! Continuing supply of hatchery produced seed oysters.! Product development especially extended shelf-life for export.! Marketing R&D; QAP’s and export certification.! Initiation of a grower’s network.! Liaison with the NSW Oyster Management Advisory Committee

A) Recommendations for improving reliability of supply, quality and cost of flatoyster spat

1. NSW Fisheries provide continuing technical support to new and existing commercialoyster hatcheries.

2. NSW Fisheries assure supply of seed flat oysters in the absence or failure ofcommercial hatcheries.

3. NSW Fisheries assist the earliest establishment of regional field nurseries by interestedfarmers to receive and on-grow small ex-hatchery spat.

4. NSW Fisheries to produce triploid spat and evaluate costs and benefits of triploidy.

B) Recommendations for improving the efficiency, reliability and versatility offarming flat oysters

1. Compile and regularly update a best practice production and post-harvest manualinitially incorporating recommended low cost and efficient practices provided on page34.

2. Evaluate floating tray, culture successfully demonstrated by John Smith at Bermagui, ata range of alternative sites on the far south, south, central and northern coasts of NSW.

3. Evaluate the effects of alternative inter-tidal and sub-tidal farming practices (especiallyeffects on growing height), farm location and seasonal survival, growth rate, fleshcondition and breeding status of flat oysters. (Include an assessment of whether theoptimum growing height for flat-oysters on inter-tidal leases is 25 to 30 cm belowcorresponding optimum heights for Sydney rock oysters (SRO) as recommended byRay Tynan for Pambula Lake).

4. Evaluate the efficacy of hatchery rearing and farming and of marketing advantages oftriploid flat oysters.

5. Identify and evaluate prospective deep water farming sites e.g. Sections of Jervis BayBatemans Bay and Twofold Bay and offshore areas.

6. Evaluate the utility of anti-foulant coatings (especially Oyster Clear) over a wider arrayof inter-tidal and sub-tidal farming techniques on existing SRO oyster leases andpotential deep water suspended and floating culture sites.

7. Encourage extension of pilot farming trials onto SRO farms on the northern and centralcoasts and into suitable bays such as Twofold Bay, Botany Bay and Jervis Bay.



8. Encourage earliest formation of flat oyster farming association(s) / collective(s) /network.

9. Encourage risk reducing farming practices such as off bottom culture crop mixing andcrop rotations. Conduct regular product testing that minimize the incidence and impactof Bonamia.

10. Undertake a survey for presence of Bonania in wild stock in estuaries in which flatoyster culture is intended. If international export is intended, then regulatoryrequirements for ensuring disease-free status defined by the OIE would need to befulfilled. As two successive years of negative testing results are required forrecognition of disease free zones, systematic collection and appropriate methods ofpreserving and archiving of samples is recommended. This strategy would facilitaterapid development of export markets if and when opportunities arises.

N.B. As two successive years of negative testing results are required for recognition ofdisease free zones, systematic collection and appropriate methods of preserving andarchiving of samples is recommended.

C) Recommendations for improving market volume and price of flat oysters

1. Develop and adopt a universal QAP relating to consumer safety (including sanitarysurveys of sites bacterial/viral testing of oysters and depuration protocols).

2. Develop and adopt a universal system for classing flat oysters according to size andeating qualities.

3. Develop and adopt best practice systems for packing, storing and transporting live andprocessed flat oysters.

4. Avoid marketing oysters during periods of poor flesh quality or when presence ofbrooders exceeds say 5%.

5. Educate the trade that unsightly black-sick or grey-sick brooders can be renderedacceptable by simply flushing them clean of larvae with clean running water.Compensate the trade for this inconvenience by discounting consignments with lowlevels (<5%) of brooders by say 5 to 10%. Also, inform the trade that unlike rockoysters, healthy flat oysters will gape.

6. Encourage establishment of centralised systems for the promotion and orderlymarketing of flat oysters locally, interstate and overseas.

7. Facilitate access to export markets through recommendation B10, C1 and by routinelytesting flat oysters grown in high salinity bays or offshore for algal bio-toxins inaccordance with current protocols being applied to commercially harvested surf clamsin NSW.

8. Promote the adoption of comprehensive recommendations for extending the shelf-lifeof flat oysters during transportation and storage produced on pp. 51-53.



2. AIMS OF THE WORKSHOP

The central aim of the workshop was to assess the intermediate to long term prospects forflat oyster farming in NSW. Issues addressed included the following:

! An evaluation of results from pilot hatchery, farming and market trials of this species inNSW and Victoria.

! Scope for use of anti-foulant coatings to combat bio-fouling problems in raft suspendedlongline and bottom tray culture.

! An evaluation of the likely impact of disease especially risks posed by Bonamiasis toproduction and export of farmed flat oysters and scope for reducing these risks.

! Scope for marketing flat oysters in NSW, interstate and overseas.! Industry development issues namely, the identification and discussion of key problems

and constraints to large-scale reliable and profitable production.! Initiation (if appropriate) of a joint government/private sector industry development

plan for large-scale production of flat oysters in NSW.

Assessing the potential for diversified production into new species was considered animportant initiative to assist the NSW oyster industry that has suffered a progressivedecline of approximately 40% in output since its peak in the mid 1970’s. The workshopmay also be considered timely in view of recent concerns over the spread of QX disease ofSydney rock oysters to the Georges River south of Sydney in 1996 and its detection in 1999in yet another estuary, the Brunswick River, previously thought free of this catastrophicdisease.



3. OPENING ADDRESS

Bill Rutledge

Director of AquacultureNSW Fisheries, Port Stephens Fisheries Centre

" 02 4982 1232; Email: [email protected]

On behalf of the Minister, who sends his apologies for not being able to attend today due toparliamentary commitments, I extend a warm welcome to all participants in this workshopon problems of producing and marketing flat oysters in New South Wales. I especiallywelcome oyster farmers who have travelled here to Sydney from points as far south as theVictorian border and as far north as Port Macquarie in their own time and at their ownexpense. I also extend a special welcome to interstate guests, Dr Rob Adlard and NeilHickman. Dr Rob Adlard, Curator of Protozoans at the Queensland Museum, is one ofAustralia’s leading experts in oyster diseases including Bonamia in flat oysters. Mr NeilHickman, Senior Scientific Reseacher from the Victorian Marine and FreshwaterResources Institute (MAFRI) will be sharing with us valuable lessons learned from fiveyears of flat oyster aquaculture research conducted in Victoria between 1986 and 1992.

NSW Fisheries is currently reviewing its role in the development of aquaculture in NSWand is seeking a much closer partnership with the private sector. The Minister isdetermined that departmental resources committed to aquaculture over the next decade willresult in substantial expansion and diversification of economically and environmentallysustainable aquaculture industries in this state.

Sydney rock oyster farming is still NSW’s dominant aquaculture industry with gross annualsales of about $28M and a labour force of around 2200. Nevertheless, the industry is undersiege having sustained a cumulative decline of about 40% in the volume and value ofproduction over the past two decades. Principal causes of this decline have been high andrising costs of producing a good quality safe-to-eat oyster that suffers the twin liabilities ofa slow growth rate (three to four years to market) and a susceptibility to two majorprotozoan diseases (winter mortality and QX). These problems have been compounded byacid sulphate soil run-off and other forms of environmental degradation of catchments andpollution of many of the major producing estuaries in NSW. Ultimately, progressivelyhigher costs of conforming to ever more arduous QAPs to safeguard consumers andincreasingly restrictive translocation regulations to counter the spread of QX disease andPacific oysters from contaminated to clean estuaries have had to be borne by farmers. Allof this has occurred over a period of rapidly increasing market competition fromTasmanian, South Australian and New Zealand grown Pacific oysters.

A continuing feature of research undertaken by NSW Fisheries in support of the ailingoyster industry, has been the development by Dr John Nell of genetically improved (fastergrowing and more disease resistant) breeding lines of Sydney rock oysters. A supportingelement to this strategy has been to provide the industry with hatchery produced seed ofother high value but faster growing species of estuarine bivalves. Foremost, amongst the



latter, over the past three years has been the hatchery production and supply of more than1.3 million seed flat oysters.

NSW Fisheries will undertake to continue to provide flat oyster spat and associatedextension and research and development services but only under the following conditions:

! that hatchery production of flat oyster spat will only continue in the absence of (or as abackup to) private sector hatchery production;

! that industry representatives at today’s workshop endorse continued effort to establish asignificant flat oyster industry and the supporting role of NSW Fisheries; and

! that consensus is reached on the identity and relative importance of constraints toexpand long term profitable and sustainable production of flat oysters and that thisinformation is used to set industry research and development priorities.



4. GENERAL INTRODUCTION AND BACKGROUND ONFLAT OYSTERS AND THEIR CULTURE

Neil Hickman, Rob Adlard, Mike Heasman* and Ian Lyall

*NSW Fisheries, Port Stephens Fisheries Centre" 02 4982 1232; Email: [email protected]

The Australian flat oyster, Ostrea angasi is a marine dwelling oyster which is very similarto the European flat oyster, Ostrea edulis, which the French refer to as “Belon Oysters”.The European oyster has been cultured since Roman times, and until relatively recently wasthe basis of a thriving European aquaculture industry. Flat oysters are different fromestuarine rock oysters such as the Sydney rock oyster (Saccostrea glomerata) and thewidely cultured Pacific oyster (Crassostrea gigas). In rock oysters, the sexes are separateand fertilisation is external, whereas Ostrea species can change sex, fertilisation occurswithin the shell and the oyster broods larvae in the gill chamber before releasing them at asize of approximately 180 microns. Rock oysters are usually found attached to rocksintertidally in estuaries, whereas flat oysters generally occur in deeper waters of marinebays and inlets and even offshore where they can often form dense beds.

In recent times, the disease Bonamiasis has devastated flat oyster culture through Europe,North America, New Zealand, and Australia. In Australia the disease has caused majorlosses of natural beds of oysters in Port Phillip Bay and along the coast in Victoria, insouthern and eastern Tasmania, and in southwest Western Australia. The disease isparticularly lethal to large reproductively active flat oysters but does not affect rock oystersor indeed any other type of bivalves tested. The French have engaged in a long program todevelop disease resistant stock. While this research is ongoing, to date there is nocommercial availability of resistant stock.

Methods for hatchery production of both flat and rock oysters are well developed andhatchery production supports many major oyster culture industries throughout the world.Traditionally oysters have been cultured on the sea bottom by spreading juveniles (spat)which have been caught in the wild on collectors such as shells (cultch). In order toimprove growth and offer protection from predators, many oyster industries now rely onbottom racks. Bottom rack culture may entail growing oysters on sticks or within a varietyof bags, baskets, cylinders or trays.

Overseas, flat oysters are readily accepted in the market place and enjoy a high reputationas a quality product.



5. PILOT COMMERCIAL HATCHERY AND NURSERYREARING OF FLAT OYSTERS IN NSW 1996-1999

Mike Heasman and Lindsay Goard

NSW Fisheries, Port Stephens Fisheries Centre" 02 4982 1232; Email: [email protected]

Introduction and Aims

The aim of pilot hatchery production of flat oysters was to enable NSW oyster farmers toevaluate this species as an alternative to Sydney rock oysters (SRO). Trial commercialfarming of flat oysters in NSW commenced in early 1998 when NSW Fisheries producedthe state’s first hatchery generated batch of seed. This initiative followed in the wake of anunsuccessful research and development funding application to help the Sydney rock oyster(SRO) farmers diversify production into flat oysters. The application submitted in 1995 toOLMA (a division of the Department of Employment, Education, Training and YouthAffairs) was prepared by NSW Fisheries in collaboration with the Tuross Lakes OysterFarmers Association and the NSW Fishing Industry Training Council. Other significantfactors prompting hatchery production and trial farming were: the very encouraging resultsof farming trials in Port Phillip conducted between 1986 and 1991; and of an evaluation ofmarkets for farmed flat oysters in Western Europe especially France and Spain by southcoast oyster farmer David Maidment in 1994.

Materials and Methods

Brooder acquisition and stripping

Four batches of seed flat oysters were produced using larvae stripped from gravid captivebrooders. These were held in suspended cages on SRO farming leases in Pambula Lake orTuross Lake in October and November 1996, December 1997 and December 1999. Theoysters were layer packed in damp absorbent paper within sealed styrene foam boxes androad freighted chilled to the bivalve hatchery at the Port Stephens Fisheries Centre (PSFC)within 24 hours. On arrival, the oysters were immediately opened and the mantle cavityand gills inspected for the presence of larval broods. Larval broods were recognised aseither: white-sick condition, indicative of the presence of early (trochophore) stage larvae;grey-sick condition, indicative of intermediate stage larvae; or black-sick condition,indicative of advanced ready-to-release larvae.

Brooders were stripped of larvae by vigorously flushing the gills and mantle cavity withseawater. The larvae were then thoroughly rinsed in seawater and stocked at the rate of 1to 2 per mL into a 20 000 L cylindical fibre-glass rearing tank at 25°C. As with flushingand rinsing of the larvae, seawater used to rear the larvae was trucked from local oceanicbeaches, aged and settled for a week or so then passed through 1 micron nominal cartridgefilter immediately prior to use.



Aerial view of Port Stephens Fisheries Centre Taylors Beach, NSW

Hatchery and nursery rearing

Standard regimes for feeding and all other elements of husbandry identical to thosedeveloped for hatchery rearing of SRO oysters (Frankish et al., 1991) were then applieduntil pedi-veliger larvae had attained competence to undergo settlement andmetamorphosis. Competence was attained at a mean larval shell height of 320-340 µm, 16to 20 days after stripping. Competent larvae were treated with epinephrine using standardtechniques (Nosho and Chew, 1991) to prompt cultchless settlement and metamorphosisbefore being transferred to 450 mm diameter oyster down-weller screens fitted with 220µm nylon mesh.

Developing juveniles were stocked onto down-weller screens at the rate of 100 000 to 200000 per screen in the hatchery. They were maintained at 25°C on a mixed diet of micro-algae until large enough to be retained on a 350 µm screen 7 to 10 days later. The dietcomprised at least one of the diatom species, Chaetoceros muelleri, C. calcitrans andSkeletonema costatum plus one or both of the prymnesiophyte species Pavlova lutheri andTahitian Isochrysis sp. Juveniles were then transferred to up-weller screens of pond fed orfield nurseries for on-rearing at ambient temperature on mixed phytoplankton blooms.Outdoor nursery rearing and associated grading onto successively larger mesh size screenswas continued until the spat had attained a minimum shell height of 8 to 10 mm suitablefor sale to commercial oyster farmers.



Results

A summary of results for flat oyster hatchery and nursery production operations in 1996,1997 and 1999 is provided in Table 1. As indicated in Fig. 1, development rates ofstripped flat oyster larvae are very similar to those of SRO larvae with the hatchery cyclefor both species most commonly spanning 18 to 22 days.

Brooder flat oyster commonly yield from 1 to 3 million larvae. This is an order ofmagnitude lower than SROs that commonly yield 10 to 30 million eggs and thence 5 to 20million “D” veliger larvae per spawner. The lower fecundity of flat oysters is howeveroffset by mean ± s.d. larval survival rates of 44 ±10% (range 37 -58%; n=4). Thesesurvival rates are more than three times rates of 15.7 ± 4.8% (range 9 to 23%; n=10)attained with SRO reared at PSFC. More importantly, no batch of flat oysters reared atPSFC to date has suffered mass mortality such as that consistently experienced over thepast 15 years with Sydney rock oysters. Diseases causing mass mortality of SROsinvariably manifests either in early (3 to 9 day old) larvae or in small juveniles below 2 mmshell height.

As indicated in Table 2, more than half a million 8 to 10 mm spat from the first twobatches were supplied to a total of six initial clients between December 1996 and March1997. More than a million spat from the third batch were supplied to a total of elevenclients including five of the six initial clients between March 1998 and February 1999. Allorders were in fact fully filled and a number of spat excess to demand discarded. Morethan two thirds (1.06 million) of spat supplied were purchased by a total of six oysterfarmers between Bermagui and Merimbula on the State’s far south coast. Three oysterfarmers at Batemans Bay and Browlee on the State’s mid south coast accounted for afurther quarter of sales (390,000). The balance of 6% of sales (93,000) were purchased bythree metropolitan or central coast farmers based at Newport, Woy Woy near Gosford andKaruah (Port Stephens).

Discussion

Since the first successful hatchery production in Tasmania (Dix, 1976), O. angasi spat havebeen produced by commercial and public sector hatcheries in Tasmania, Victoria, SouthAustralia and Western Australia. Reported hatchery production difficulties are largelyconfined to reports of heavy mortality of early juveniles from Victoria (Hickman andO’Meley, 1988) and more advanced juveniles from Bonamiasis in Western Australia(Bilton, pers. com.). The heavy losses of larvae and early juveniles reported by Hickman(1998) were ascribed to adverse effects of the disease Bonamia on larval vigor. Asrecommended by Hickman (pers.com., 2000 and this publication) routine screening ofbroodstock for Bonamia by hatcheries should be imposed as the first line of defense fromthis potentially devastating disease (also see Adlard this publication).

From the NSW Fisheries experience, the reliable supply of seed appears to bestraightforward. The breeding season of O. angasi in Port Phillip Bay, as indicated by thepresence of brooding females, begins in mid Spring and extends to mid Summer(September/October to January/February) with peak brooder abundance from October toDecember (Hickman and O’Meley, 1986). In South Australia (O’Sullivan, 1980) the flat



oyster breeding season extends longer (October to March) while in Tasmania it is thoughtto occur a little later (Dix, 1976). All hatchery production of flat oysters at PSFC to datehas been conducted between October and December. However, high abundance ofbrooders reported to occur as early as June in far southern NSW (Tynan, pers. comm.,2000) is indicative of a considerably longer (June to December) spawning season.Accordingly, it is likely that hatchery and nursery operations in NSW could, if required, bemore protracted and timed to generate a supply of seed to farmers in mid to late Springthereby enabling maximum utilization of the late Spring (November) to late Autumn (May)period of high growth rates.

Acknowledgements

The authors wish to acknowledge the contributions of John Diemar, Melissa Walker, IanDiemar and Lynne Foulkes in the hatchery and nursery production of flat oyster at the PortStephens Fisheries Centre between 1996 and 2000. We also thank David Maidment forproviding the original impetus for these activities and Ray Tynan for the supply ofbroodstock flat oysters.

References

Dix, T., 1976. Laboratory rearing of larval Ostrea angasi in Tasmania, Australia. J.Malac. Soc. Aust. 3, 209-214.

Frankish, K.R., Goard, L.J., O’Connor, W.A., 1991. The Development of HatcheryRearing Techniques of the Sydney Rock Oyster (Saccostrea commercialis)Department of Agriculture New South Wales at the Brackish Water Fish CultureResearch Station, Salamander Bay, NSW, 2301. 27pp.

Hickman, N., 1998. Flat Oyster Aquaculture. A summary of past research in Victoria.Report prepared for The Aquaculture Section, Fisheries Victoria, Dept. Nat.Resources and Envir. 14pp.

Hickman, N.J., O’Meley, C. M., 1988. Culture of the Australian Flat Oyster (Ostreaangasi) in Victoria. Final Report FIRTA 84/77. Internal Report No. 172.Department of Conservation Forests and Lands, Fisheries Division.

Nosho , T. Y., K. K.Chew, 1991. Remote setting and nursery culture for shellfish growers.Workshop Record. Feb, 19 Olympia, Washington. Publ. Washington Sea GrantProgram, University of Washington. Seattle 98195. 69pp.

O’Sullivan, B. W., 1980. The fertility of the Port Lincoln oyster (Ostrea angasi Sowerby)from West Lakes South Australia. Aquaculture 19, 1-11.



Fig 1. Hatchery growth of Sydney rock oyster and flat oyster larvae

0

100

200

300

400

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Days

Larv

al S

hell

Hei

ght(m

icro

ns)

Flat Oyster Sydney Rock Oyster

Table 1. Summary of hatchery rearing data for Ostrea angasi at PSRC

Date 25/10/1996 19/11/1996 23/12/1997 16/12/1999

Source of broodstock Pambula Pambula/Tuross Pambula PambulaTotal number of broodstock examined 6 ? ? 140Number of Brooders 1 8 6 grey/black 2 black / 3 white-sickNumber larvae stripped (million) 2.28 12.1 14 3.62 / 4.44 (1.28'D')Mean fecundity (million) 2.28 1.51 2.33 1.81 / 1.48Hatchery Tank volume (litres) 2 x 1000 10,000 20,000 20,000Number of larvae to set (million) 0.85 4.22 8.18 2.885 (combined)Larval survival % 37.3 34.8 58 46.8Number of spat (million) 0.443 3 3.78 1.4Set rate % 66 71 46 48.5

General: Black-sick larvae have been stripped from oysters 75 mm to 150 mm shell height.Fecundity of individually stripped black sick oysters ranges from 0.475 to 2.28 million.



Table 2. Flat oyster spat supplied by NSW Fisheries to clients since December 1996

First & second batch supplied December 1996 to May 1997SIZE 8-10 mm spat

Location Region Number of FO'ssupplied

Pambula Lake Far South Coast 200 000Dalmeny Far South Coast 16 500Batemans Bay South Coast 50 000Batemans Bay South Coast 150 000Bermagui Far South Coast 50 000Pambula Far South Coast 100 000

Total: 566 500

Third batch supplied March 1998 to February 1999SIZE 6-8 mm spat

Woy Woy Central Coast 10 000Pambula Lake Far South Coast 10 000Karuah Central Coast 33 000Narooma South Coast 50 000Pambula Lake Far South Coast 100 000Merimbula Far South Coast 33 300Dalmeny Far South Coast 250 000Pambula Far South Coast 200 000Bermagui Far South Coast 100 000Browlee South Coast 100 000Batemans Bay South Coast 90 000

Total: 876 300

Fourth Batch - Supply pending April 2000



Bivalve hatchery at PSFC

Lynne Foulkes, Fisheries Technician, Algal Production Unit, PSFC.



Nursery upweller unit, Wanda Head, Port Stephens

Close-up of 5 mm juvenile flat oysters on upweller screen



6. PRACTICAL EXPERIENCE GAINED FROM TRIALCOMMERCIAL FARMING OF FLAT OYSTERS INNSW



The following account of practical experience gained from trial commercial farming of flatoysters in NSW since 1997, is based primarily on notes compiled from a non-scripted talkat the workshop given by Pambula Lake oyster farmer Mr Ray Tynan. It also incorporatesa brief talk given by Port Macquarie oyster farmer Mr Laurie Lardner and commentsprovided by several other oyster farmers involved in pilot flat oyster farming over the pastthree years. The latter includes very useful information provided before, during and overthree weeks immediately following the workshop. Those south coast farmers providingadditional comments included Chris and Shelley Boyton from Pambula, Stephen Pascaladisfrom Bateman’s Bay, John Smith from Bermagui and David Maidment from Dalmey.

In 1997, a total of 100,000 flat oyster spat in the range 8 to 10 mm were supplied to RayTynan by NSW Fisheries as two consignments in early January and February 1997. Thefollowing year (1998) another 100,000 spat in the range 6 to 8 mm were supplied as asingle consignment in late March. In all cases, spat arrived in apparent good health afterbeing packed in damp absorbent paper inside styrene foam eskies. Spat were kept chilledduring 24 to 36 hours road transportation from Port Stephens to Pambula Lake by theinclusion of soft gel freezer packs. On arrival, the spat were immediately stocked into 35litre capacity “Stanway cylinders” (“tumblers”) at the rate of 1-1.5 litres of spat percylinder. Tumblers were slung from rails of existing Sydney rock oyster racks on a lowmudworm incidence lease located at Pambula Lake. Effective growing heightapproximated 0.5 m above zero datum. This height reduced protracted exposure of theoysters to drying or extremes of temperature. During their final phase of nursery rearing inthe cylinders spat were grown from initial shell height of 6 to 10 mm to final size above 20mm suitable for final grow-out in 14 or 17 mm mesh plastic oyster baskets or trays. Thisphase ranged from three months, in the case of spat stocked in early January that benefitedfrom high growth promoting temperatures from mid Summer and early Autumn, to 6-9months for spat stocked in late March that required over-wintering in cylinders.

In spite of infrequent inspections, grading and thinning, the tumbling action of thecylinders ensured that the spat acquired a good circular cup shape. The tumbling andwashing action of cylinders kept the spat free of significant over-catch and other bio-fouling. The spat also remained free of mud-worm and invertebrate predators such asoyster drills, flatworms, crabs and starfish that could enter the cylinders as planktoniclarvae.

The spat were next stocked either into shallow fully enclosed mesh trays mounted on racksat the same height as the tumblers or into baskets. There they were maintained until



attaining a minimum shell height of 70 to 80 mm, suitable for marketing. Lack of regulargrading and thinning of oysters in partitioned trays and baskets resulted in variable sizes.Accordingly, time to reach marketable size of 70 to 90 mm ranged from 15 to 24 monthsfrom receipt of spat. As with rearing in cylinders, tray and basket reared flat oysterssuffered little mortality through predation, mudworm infestation or disease (no wintermortality). Significant stock losses occurred as a consequence of starvation andsuffocation associated with overcrowding and lack of cleaning or though inadvertentexposure to heat stress during handling operations. Some serious losses were alsosustained as a consequence of inattention to trays or baskets that had dropped into the mudbelow or adjacent to the racks. Recent (Autumn 2000) losses of trays on racks are a littlehigher than usual leading Ray Tynan to recommend that racks for flats should be 25 to 30cm lower than normal SRO racks but still well clear of the mud.

Ray Tynan’s experience however contrasted with attempts by Laurie Lardner to farm flatoysters in trays suspended beneath rafts in the Hastings River at Port Macquarie. Seed flatoysters received in September 1998 at 7 mm exhibited exceptional growth reaching a meansize of 50 mm during the following three months (October to December 1998). Howeverheavy and uncontrolled bio-fouling by sea squirts (conjevoy), barnacles and spongescurtailed subsequent growth and development and marketing of the product. It isnevertheless likely that bio-fouling of these raft cultured flat oysters could have beencontrolled if a simple bio-fouling control technique used by other farmers had beenadopted. The latter comprised air exposure of flat oysters within mesh oyster trays for upto three days. This practice according to both Ray Tynan and Chris Boyton was quite safefor juvenile flat oysters above about 30 mm shell height, provided they were stored in acool shady place.

In response to a question from Steve McOrrie (NSW Fisheries), Chris Boyton corroboratedRay Tynan’s experience that flat oysters could be safely grown at least for short periods atnormal growing height on his Sydney rock oyster racks at Pambula Lake and that he hadpersonally used this practice to harden them prior to harvesting and transportation.Questioned about mud worm and other problems usually encountered with subtidal culture,Ray Tynan responded that no serious mud-worm or bio-fouling problems have beenencountered on his leases at Pambula Lake provided that the oysters were kept above themud.

Ray Tynan also said that juvenile flat oysters successfully endured protracted falls insalinity generated by record rainfall during 1998. Much the same experience was reportedby Bermagui oyster farmer John Smith for an initial batch of flat oysters received in May1997. However an entire batch of 100 000, 6 to 8 mm spat received by John Smith inMarch 1999 died after being exposed to near fresh conditions within a fortnight of theirarrival.

Another very encouraging report from John Smith was that his first consignment of flatoyster spat had attained jumbo sizes (shell heights in the range 15 to 20 cm) after being on-grown for only two years in sub-surface oyster trays slung below moored floats constructedfrom 100 mm diameter PVC storm-water pipe.

Major problems were experienced by all pilot-farming operations in packaging,transportation and marketing of flat oysters. The most significant of these was high



variability in the size and condition of the oysters, especially the presence of unsightlyblack-sick and grey-sick brooders amongst market consignments. These problems havebeen exacerbated by very adverse reaction of buyers to gaping of flat oysters which isexhibited within a few hours of their removal from sea-water. In contrast to flat oysters,gaping in rock oysters only occurs after a week or more of their removal from inter-tidalleases and is indicative of actual or impending death.

All of the above quality problems encountered were attributed by Ray Tynan to a poorunderstanding of seasonal variability in the general and breeding condition of flat oysters incombination with inadequate frequency and intensity of thinning, grading, and cleaningoperations. The latter arose mainly from staff shortages created by competing demands ofhis “bread and butter” Sydney rock oyster production activities. Lack of time and labour todevote to product quality control and to marketing and promotion were also cited as criticalproblems by several other workshop participants engaged in pilot flat oyster farmingoperations on the south and far south coast of NSW.

An almost total absence of communication or collaboration between the 11 oyster farmersinvolved in trial production of flat oysters over the past three years was generallyacknowledged by workshop participants as a major and continuing impediment to theemergence of a significant flat oyster sector within the NSW oyster industry. Indeedconsensus was reached that ignorance of appropriate post-harvest protocols (packaging,transportation and storage) and ad hoc supply, together with lack of cohesive marketingand promotional strategies, have collectively undermined development of strong consistentdemand for farmed flat oysters by the local (Sydney and Canberra) restaurant trade (seecompanion comments by Martin Palmer and Nick Ruello in the next section).



7. NOVEL TECHNOLOGIES FOR THE REDUCTION OFBIOFOULING IN SHELLFISH AQUACULTURE

Sophia McCloy and Rocky de Nys

Centre for Marine Biofouling and Bio-Innovation,University of New South Wales


Shellfish culture represents a large portion of the Australian aquaculture industry, withpearl and edible rock oysters the most important sectors. As with other areas of theindustry, bio-fouling - the settlement and growth of unwanted marine organisms - reducesprofitability by increasing the costs associated with cleaning and maintaining shell andequipment.

The current methods for the control of bio-fouling on pearl oysters (Fig. 1), involvesindividual cleaning of shell every 7-14 days. The frequent cleaning rate required is due tothe high level of settlement and growth of barnacles, mussels, and infection by boringsponges. This regime increases all associated costs such as labour and equipment andcontributes to a reduction in growth and nacre production of pearls from increasedhandling. In terms of value, the industry loses an estimated $25 million/year in direct andindirect cost of biofouling and its control.

As with pearl oysters, a major problem for farming of edible oysters, including flat oysters,is the control of fouling, especially barnacles and oyster over-catch. The latter are majorcontributors to increased labour associated with cleaning of shells and racks, loss of oystergrowth and increased mortality. The control of bio-fouling would greatly improve thefeasibility of sub-tidal culture of bivalves, including flat oysters, which can enhance growthand also increase marketability and export value.

These concerns initiated an investigation into the prevention of bio-fouling on shellfish andassociated equipment. For the last three years, the Centre for Marine Bio-fouling and Bio-Innovation, at the UNSW and the CRC for aquaculture in collaboration with industry(Tasmanian Salmon Growers Association, Oyster Research and Advisory Committee, PearlProducers Association), government (NSW Fisheries, CSIRO) and a commercial partner(Wattyl Australia) have established a research and development program to provideindustry with a cost effective solution to fouling.

The two main programs of research are:

1) the development of environmentally friendly anti-fouling coatings that can be appliedto shellfish, oyster racks, mesh and netting; and

2) the development of extruded anti-fouling polymers for the manufacture of mesh, netsand trays.



The project goal is to provide industry with a cost-effective solution to fouling. Thisinvolves the use of an anti-fouling for coating the shells of pearl and edible oysters andassociated farm equipment. By combining knowledge gained from both the edible oysterand pearl oyster research, this had resulted in considerable success in producing coatingsthat as well as being non-toxic to the oysters and the environment, are cost-effective andeasy to apply.

The pearl oyster program has developed a treatment for the infection of pearl shell by theboring sponge, Cliona. Approximately 10% of farmed shell are infected by this spongewith almost all infected shell dying. Results from trials, conducted in Broome WA, showthat two weeks after the treatment by PearlSafe, a product developed within the program,90% of the heavily infected shell were free of the sponge and after four weeks none of theshell were re-infected.

Trials have been undertaken in the edible oyster industry we have undertaken trials for thelast two years at three locations along the coast of NSW, Sydney, Port Stephens and PortMacquarie. These trials were instrumental in the step-by-step refinement of initial coatingformulations with the aim to improving the efficacy, adhesion and integrity of each coatingat each trial.

The work conducted in Sydney involves both laboratory and initial field trials to evaluatethe integrity and adhesion of new and improved coatings, alternative cost effectiveapplication methods and the general efficacy of the coatings against the settlement of arange of fouling organisms. The laboratory assays test new coatings against the settlementof oysters (Figs. 2 & 3) and barnacles. The best of these coatings are then further tested infield trials. In the latest Sydney based trial, at Walsh Bay, the best coatings have beenfound to inhibit the settlement of barnacles and other fouling organisms for up to 12 weekswhile maintaining excellent adhesion and integrity (Fig. 2).

Once trials have been completed in Sydney, the best coatings are tested on site at PortStephens and Port Macquarie under commercial farming conditions. Trials completed atthese sites showed that coatings inhibited oyster over-catch for up to 21 weeks at six out ofeight sites and 15 weeks at the remaining two sites.

At this time (March, 2000) latest coatings are being tested at Port Macquarie and arewaiting for oyster spat-fall to occur. Although these coatings need improvement againstthe settlement of barnacles, their integrity and adhesion to both the oysters and racks isexcellent. Furthermore, the surface characteristics of the coatings allows for easy removalof any organisms that do successfully settle on oysters. Significant progress has been madein improving overall performance of current coatings. Approval to use the coatings onedible oysters has also been applied for under a “minor use permit” with the NationalRegistration Authority. An industrial partner, Wattyl Australia Ltd, will be able to providea commercial product to be called “Oyster Clear” (Fig. 4) to the NSW oyster industry foruse on both rock oysters and flat oysters within the next one to two years.



Control

Coating

Figure 1. Pearl oysters with and without anti-foul coating



0

10

20

30

40

Num

ber

of b

arna

cles

Control 13 14 15 17 16 18

Treatments (after 12 weeks)

Figure 2. Comparison of different types of anti-foul coatings and untreated control forSydney rock oysters



Figure 3. Sydney rock oyster with over-catch

Figure 4. Sydney rock oysters protected from bio-fouling with Oyster Clear coating



8. BONAMIA SPP DISEASE OF FLAT OYSTERS

Robert Adlard

Curator of ProtozoaQueensland Museum, Brisbane


Introduction and Background

Bonamia spp. are protozoan parasites found within the blood cells of flat oysters. They aretiny cells, generally 2-3 micrometres (0.002 to 0.003 mm) in diameter, and can occur singlyor in numbers as great as 10-20 within an individual blood cell. The onset of infection isoften associated with inflammation in the oyster tissues. Affected blood cells accumulatein vascular sinuses but may be seen in all tissues in heavy infections (Balouet, Poder &Cahour, 1983; Elston, Farley & Kent, 1986). As the disease progresses, infected cellsaggregate and form lesions in the tissues, particularly within the gills, but later in thedigestive gland and at the edges of the mantle. The blood cells become necrotic and die,with death of the oyster probably related to its ability to replace infected blood cells at atime when energy reserves are depleted though spawning. The infection can cause anassociated inflammatory response in the host which is shown by an increase in the numberof granulocytic amoebocytes, however, inflammatory responses of unknown origin occurfrequently in oysters and cannot be used as an indication of the presence of Bonamia (seeElston et al., 1986).

Bonamia can be transmitted experimentally through injection of infected oyster tissue intoan uninfected oyster; by immersion in water containing macerated infected tissue; and byassociation with infected oysters in the same aquarium (Bucke, 1988). In naturalpopulations transmission appears to be direct i.e. there is no evidence that an alternate hostis required for the life cycle, and the organism can spread rapidly in densely cultivatedpopulations of oysters. For example, Bonamia ostreae was associated with mortalities ofup to 80% within about 6 months of introduction into a population of oysters in France(Balouet et al., 1983).

Europe

The first recorded instance of a species of Bonamia was from flat oysters in France in 1979(Comps, Tige & Grizel, 1980). Significant mortalities of the cultured flat oyster, Ostreaedulis, have since been attributed to the disease in France, Spain, England, Ireland,Denmark, Netherlands, and in North America (Balouet et al., 1983; Bucke & Feist, 1985;Elston et al., 1986; Van Banning, 1985). The disease is thought to have originated inNorth America and spread via oyster spat imported to France and from there to otherEuropean countries (Elston et al., 1986). Large amounts of oyster seed (Ostrea edulis)were transferred from California to France prior to 1979. Concern by government agenciesfor the containment of infectious shellfish diseases, was apparently not sufficient to preventthe introduction of such a serious pathogen into Europe in the late 1970's.



New Zealand and Australia

From late 1985 until the present, large scale mortalities have occurred among dredged bluffoysters (Tiostrea chilensis) in Foveaux Strait, south of the South Island of New Zealand,reducing the population of commercial sized oysters from 1974 levels (1,600 x 106), to justbelow 20% of that in 1992. Mortalities were associated with an outbreak of ahaplosporidian parasite which occurred in haemocytes, apparently lacked a spore stage,resembled Bonamia ostreae in the European flat oyster, Ostrea edulis, in Europe butshowed specific differences to it, and was therefore called Bonamia sp. (Hine, 1991a).Indications are that Bonamia sp. spreads slowly in currents in the wild (Foveaux Strait, 70Km in six years), while in contrast, human intervention has spread the parasite over largedistances. In the summer of 1991, an ultrastructurally identical and genetically similarparasite to that found in New Zealand, was found in the haemocytes of Ostrea angasi inPort Phillip Bay and along the coast in Victoria, in southern and eastern Tasmania, and insouthwest Western Australia, and has been associated with large scale mortalities of thehost oyster. Thus, two distinct species of Bonamia are currently known, Bonamia ostreaein Europe and Bonamia sp. in Australasia.

Susceptibility of Bivalve Species

The question of susceptibility of other species of bivalves to Bonamia sp. has implicationsfor the movement of bivalves between areas. In a recent study in the UK (Culloty et al.,1999), the Pacific oyster (Crassostrea gigas), two species of mussels (Mytilus edulis, M.galloprovincialis) and two species of clams (Ruditapes decussatus, R. philippinarum) weretested for their susceptibility to the European parasite Bonamia ostreae. None of thesespecies could be infected with the parasite either naturally by association with infectedoysters or experimentally through inoculation or association. Earlier studies (Bucke et al.,1984) have shown that Tiostrea chilensis, the New Zealand dredge oyster, could beinfected with the parasite Bonamia ostreae, normally found in Ostrea edulis the Europeanflat oyster. Furthermore, in 1984 (Bougrier et al.) the Australian flat oyster, Ostrea angasi,was tested for susceptibility to pathogens in France and became infected not only with theEuropean parasite, Bonamia ostreae, but also with Marteilia refringens, and was found tobe highly susceptible to another haplosporidian parasite which occurred in France.

Thus, Bonamia sp. have been transmitted between species of flat oysters but not betweenother bivalves. As an addendum to that, in 1998 there was a report from France of aBonamia-like parasite found in Crassostrea rivularis held in aquarium quarantine(Cochennec, 1998). In the OIE (Office Internationale des Epizooties) diagnostic manual'all species of Ostrea and Tiostrea and all ostreids should be considered susceptible'.

Seasonality

Mike Hine's (Hine, 1991b) work in New Zealand has identified a seasonal cycle ofinfection in Bonamia sp. The first phase is referred to as incubation (September toNovember) when oysters become infected by dense swarms of the parasite taken in whenfeeding. This phase is difficult to diagnose and the disease is subclinical. The secondphase, or proliferation phase (December to May) occurs after spawning in the oyster,during which time the parasites divide by binary fission and proliferate. It is during thisphase in which the greatest mortalities occur. The third phase is termed plasmodial (June



to August) and shows a decreased necrosis of blood cells in the oyster and most parasitesbecome dense and necrotic.

Taking into account this seasonal cycle, any attempt to detect the presence of Bonamia ineither wild or cultured oyster stock for risk assessment or as part of a surveillance programshould be undertaken between January and April when the probability of detecting apositive oyster is highest.

Breeding for Disease Resistance

In France research showed some success in breeding resistant lines of the European flatoyster. Protocols were first developed for purifying Bonamia ostreae and inoculating theparasite into test strains of oysters (Mialhe et al., 1988). Then a combination of massselection, parasite inoculation and natural infections were used, to produce at least onestrain (a 3rd generation cross) which showed four times the survival of a control groupwhile also tending towards higher growth rates than that shown by the control group(NaciriGraven et al., 1998). However, this research is ongoing and resistant stock are notyet commercially available.

Regulations on Movement

Bonamia is a notifiable pathogen to the OIE and there are restrictions on movement fromBonamiosis-infected zones to disease-free zones and as well as requirements forestablishing the status of oyster stock from each zone. OIE regulations require that stockbe tested to a level of 2% prevalence at 95% confidence i.e. from each defined population,a minimum of 150 specimens should be sampled for diagnosis and all must be founddisease free. Wherever possible one sample (of ≥150) should be taken from naturallyoccurring oysters to establish endemicity in an area. At least three sites should be sampledfrom each designated 'zone' i.e. a minimum of 150 oysters from each of three representativesites within the zone. Disease free status needs to be established over two successive yearsfor a designated zone to be formally recognized as disease free and annual testing isrequired to maintain disease free recognition.

Diagnosis can be either from histology (tissue sections) or from tissue imprints of the heart(see OIE diagnostic manual). However, in the Australian species there is evidence that theparasite does not produce systemic infections so imprints of other (epithelial) tissues and oflesions in the mantle or gills should be made for routine diagnosis.

Recommendation

There is no doubt that Bonamiasis poses a threat to farming flat oysters. As such, it wouldbe advised to at least undertake a survey for its presence in wild stock in estuaries in whichflat oyster culture is intended. If international export is intended, then regulatoryrequirements for ensuring disease-free status defined by the OIE would need to be fulfilled.As two successive years of negative testing results are required for recognition of diseasefree zones, systematic collection and appropriate methods of preserving and archiving ofsamples is recommended. This strategy would facilitate rapid development of exportmarkets if and when opportunities arises.

References



Balouet, G., Poder, M., Cahour, A., 1983. Haemocytic parasitosis: morphology andpathology of lesions in the French flat oyster, Ostrea edulis L. Aquaculture 34, 1-14.

Bougrier, S., Tige, G, Bachere, E., Grizel, H., 1986. Ostrea angasi acclimitization toFrench coasts. Aquaculture 58, 151-154.

Bucke, D., 1988. Pathology of Bonamiasis. Parasitology Today 4, 174-176.

Bucke, D. et al., 1984. A report of Bonamia ostreae in Ostrea edulis in the UK. ICES CM1984/K:9, 7pp. (cited in Bucke, 1988).

Bucke, D., Feist, S., 1985. Bonamiasis in the flat oyster, Ostrea edulis, with comments onhistological techniques. In: Ellis et al. (eds.) Fish and Shellfish Pathology,Academic Press, London. pp 387-392.

Cochennec, N., Renault, T., Boudry, P., Chollet, B. A., Gerard, A., 1998. Bonamia-likeparasite found in the Suminoe oyster Crassostrea rivularis, reared in France.Diseases of Aquatic Organisms 34, 193-197.

Comps, M., Tige, G., Grizel, H., 1980. Etude ultrastructural d'un protiste parasite del'huitre plate Ostrea edulis L. Compte Rendu de l'Academie Science, Paris 290, 383-384.

Culloty, S.C., Novoa, B., Pernas, M., Longshaw, M. Mulcahy, M.F., Feist, S.W., Figueras,A., 1999. Susceptibility of a number of bivalve species to the protozoan parasiteBonamia ostreae and their ability to act as vectors for this parasite. Diseases ofAquatic Organisms 37, 73-80.

Elston, R.A., Farley, C.A., Kent, M.L., 1986. Occurrence and significance of bonamiasisin European flat oysters Ostrea edulis in North America. Diseases of AquaticOrganisms 2, 49-54.

Hine, P.M., 1991a. The annual pattern of infection by Bonamia sp. in New Zealand flatoysters, Tiostrea chilensis. Aquaculture 93, 241-251.

Hine, P.M., 1991b. Ultrastructural observations on the annual infection pattern ofBonamia sp. in flat oysters Tiostrea chilensis. Diseases of Aquatic Organisms 11,163-171.

Mialhe, E., Bachere, E, Chagot, D., Grizel, H., 1988. Isolation and purification of theprotozoan Bonamia ostreae (Pichot et al. 1980), a parasite affecting the flat oysterOstrea edulis L. Aquaculture 71, 293-299.

Naciri-Graven, Y, Martin, A.G., Baud, J.P., Renault, T., Gerard, A., 1998. Selecting theflat oyster Ostrea edulis (L.) for survival when infected with the parasite Bonamiaostreae. Journal of Experimental Marine Biology and Ecology 224, 91-107.

Van Banning, P., 1985. Control of Bonamia in Dutch oyster culture. In: Ellis et al. (eds.)Fish and Shellfish Pathology, Academic Press, London. pp 393-396.



9. REVIEW OF FLAT OYSTER AQUACULTURERESEARCH IN VICTORIA

Neil Hickman

Victorian Department of Natural Resources and Environment ProgramMarine and Freshwater Resources Institute, Queenscliff" 03 5258 0336; Email: [email protected]

During the late 1980’s and early ‘90’s several research programs were conducted byMAFRI with a view to establishing a culture industry for the Flat Oyster. The processfollowed was that which led to establishing the Port Phillip Bay mussel culture industry inthe early 1980’s. Brief summaries of the main programs are presented below.

N.B. Copies of the four reports from which these summaries are drawn together with anassociated video of nursery and farm experiments shown during the workshop have beenmade available to NSW Fisheries for distribution to NSW oyster farmers, processors andother interested parties.

9.1. Culture of the Australian Flat Oyster (Ostrea angasi) in Victoria (Hickman N.J.and O’Meley C.M. 1988a)

This initial Victorian research program aimed to develop a culture industry for the nativeflat oyster (Ostrea angasi) in Victoria. The two broad objectives of this program were todetermine the best method of obtaining a regular supply of oyster spat, and to determine thebest methods and areas for on-growing native oysters for human consumption.

Initially studies of the natural reproductive cycle and larval settlement of O. angasi in PortPhillip Bay were conducted. Gonad development occurred from May to July andoverlapped with maturation which extended from May to February. O. angasi broodedlarvae from October to December and were spent during summer (December to February)when the main larval settlement occurred. The larvae settled on hard substrates not alreadycolonised by other organisms. Attempts to catch commercial quantities of oysters in thewild were unsuccessful because the oysters became too overgrown with marine foulingorganisms. A trial to settle oysters in a marine “spatting pond” was also unsuccessfulbecause important variables such as temperature, salinity and phytoplankton species couldnot be controlled adequately. However, a pilot-scale hatchery was developed (see Hickmanand O’Meley 1988b) which ensured that sufficient O. angasi seed was available forresearch and growth trials by prospective oyster farmers who held experimentalaquaculture permits.

The growth patterns of O. angasi were typical of the Ostrea species, namely, growth rateshigh in summer and low in winter. The explanation for this seasonal pattern is that shellgrowth is controlled by temperature rather than by food availability. In Port Phillip Bay,the oysters’ condition was good during April - October, but was best during the fourmonths May - August. These months make up exactly the same season that O. edulis is inbest condition in the Northern Hemisphere. However, studies of oyster meat yields has



shown considerable annual variability in the levels of particulate food for oysters; themonths when oysters are fat; and the fatness of oysters at different sites. This variability islikely to have a marked effect on the number of months during which top quality oysterscan be produced each year. The method used to grow oysters will also have a big impacton meat yields depending on whether water flow past the growing oysters is retarded orenhanced by the growing method used.

In Port Phillip Bay, O. angasi grew equally well in mid-water and bottom racks when sub-surface floatation was used, but were stunted when grown in bags suspended on surfacelong-lines in exposed waters. A preliminary study showed that location had a markedeffect on growth rate. The husbandry technique for bag-grown oysters which mostimproved the oysters’ growth rate was density reduction. Density was found to be moreimportant than grading of oysters by size in promoting faster growth. Holding oyster seedin land-based nursery upwellers for several months did not affect the oysters’ subsequentgrowth at sea, whereas planting out oyster seed in early summer shortened their time tomaturity to less than two years at the latitude of Port Phillip Bay (38°S 145°E). When weselected the fastest growing siblings in the nursery, the growth rate of the resulting adultoysters was no better than that of the slowest growing siblings in the nursery.

This program has demonstrated that hatchery production which produces seed early in thegrowing season and simple animal husbandry are capable of dramatically improving thegrowth performance of O. angasi. In our opinion, in the medium term these procedureswill be much more useful to oyster farmers than any advances likely to result fromselective breeding programs designed to enhance growth rates. This is because the factorsreported here have a compounding effect which together can shorten the grow-out periodby several years. It is not likely that any genetic manipulation will generate such greatimprovements in growth performance.

During the course of growth trials throughout the State to identify the best growing areas,massive summer mortality was caused by Bonamiasis. This also coincided with a programto investigate larger scale commercial production (see Reilly and Hickman, 1994).

9.2. Hatchery and Nursery Production. (Hickman N.J. and O’Meley C.M. 1988b)

This report described the design and operation of a pilot scale hatchery and nursery for theAustralian Flat Oyster. The facility was located at Queenscliff (38o16’S, 144o39’E) whichis near the entrance to Port Phillip Bay, Victoria. A description was given of the six basicsystems which made up the hatchery, namely: algal culture; heating and temperaturecontrol; broodstock conditioning; larval rearing; larval settlement; and spat rearing.Procedures for operating each system were reported. Innovative features which improvedproduction were: feeding larvae and young spat only with actively growing (log phase)algal cells; accurate measurement of feeding rates by measuring fluorescence of the watercontaining the micro-algal food; using automation to routinely measure growth rates; andincluding the diatom Chaetoceros gracilis in the diet of spat.

The hatchery was operated for five seasons from 1987 to 1991 and produced experimentalquantities of seed for research and on-growing by prospective oyster farmers. An attemptto produce commercial quantities of seed for industry in the last two years wasunsuccessful, due to unexplained high mortalities of larvae and spat in these years. Given



that these were the years which preceded the discovery of Bonamia in 1991 it is possiblethat the broodstock oysters obtained from the wild were already suffering from Bonamiasiswhich could have resulted in poor quality larvae being produced.

9.3. Development of Commercial Field and On-growing Systems for Production ofthe Flat Oyster (Ostrea angasi) in Open Waters. (Reilly, D. and Hickman, N.J.1994)

This study was conducted by the Victorian Fisheries Research Institute (now MAFRI) inconjunction with the Australian Flat Oyster Company. The main conclusions from twoareas of investigations are as follows:

Nursery Production of O angasi:

1. A field nursery tumbler has great potential to increase the profitability of an oyster farmby:

a) Allowing the grower to purchase hatchery produced seed at a much smaller sizeand hence cheaper cost.b) Potentially saving a whole year on the grow-out by producing 10 mm seed earlyin the growing season.c) Allowing the over-wintering of large quantities of seed with minimalmaintenance costs.d) Satisfying what the hatchery wants to sell [small sized seed] and what thegrower wants to purchase [large sized seed].e) Converting 2 mm sized seed to 10 mm sized seed with minimum labour costs(This represents a saving of approximately $20,000 for every million seedpurchased).

2. Nursery 'corfs' used in shallow warm water have the capacity to produce large numbersof juvenile oysters if 10 mm sized seed can be made available prior to the main summergrowing season. This early season 10 mm seed production will now be possible byusing the field tumbler.

Grow-out of O angasi:

1. Traditional bottom growing and bottom rack methods would not produce oystersquickly enough to minimise losses due to Bonamiasis which is a disease which killsmature oysters.

2. Development of a new suspended culture method produced exceptionally fastgrowth rates with low mortalities.

3. The use of husbandry techniques to grow flat oysters quickly is proposed as amanagement tool to control the disease Bonamiasis which has devastated flat oysterproduction throughout the world.

The longline dropper growing method which produced exceptionally fast growth rates andthe results from this trial are shown in the following figures which are taken from Reillyand Hickman (1994).



1 2 3Seed oyster Place

glueAttach mesh

Tag gun

Packing tape

detail

Oysters 1cm apart

"droppers"

frame

long-line

sea surface

sea bed

Figure 1. Method of gluing mesh to individual seed oysters, and attaching them topolypropylene packing tape with plastic tag pins. Tapes are suspended from long-lines asvertically hanging 'droppers'.



Figure 2. Exceptional annual growth of the whole population of O. angasi grown bysuspended culture.

OCTOBER 1989 APRIL 1990Length[mm] Bags Droppers Bags Droppers

27

37

47

57

67

77

87

97

27

37

47

57

67

77

87

97

Relative frequency Relative frequency

Figure. 3. The growth of O. angasi on long-line droppers for six months shows that thewhole population attain commercial size (> 70 mm), in marked contrast to oysters grown inbags.



The whole population grown on dropper tapes became commercial size in just one growingseason. The shells were of an excellent uniform shape and not impacted by mud worm.The meat yield was also high. This presents a challenge for hatcheries and nurseries toproduce seed oysters early in the first summer. This would allow grow-out to occur withintwo years.

The grow-out principles demonstrated by this work would need to be automated in order togrow commercial quantities of oysters. The method also offers potentially large capital andlabour saving costs, which are associated with bottom rack culture. This is because of thenecessity to continually grade oysters and reduce densities in order to improve growthrates. More and more racks and containers are required as the oysters mature, and in manyestuaries the density of oysters in bags and the density of racks in the farm can severelyimpact meat yields if the carrying capacity of the estuary is exceeded. This will not be asdamaging a factor if oysters are individually suspended in mid water with much betteraccess to their phytoplankton food. By growing them in midwater individually attached togrowing lines, they are never subjected to over-crowding or having water flow reduced bycontainers which provide an attractive surface for marine fouling organisms.

Recommendations for further development on Flat Oyster aquaculture technology

Flat oysters have been the basis of several large marine aquaculture industries throughoutthe world. However, the disease Bonamia has been a major constraint to worldwideculturing of Ostrea species in recent years and will need to be addressed before industriesfor flat oyster cultivation can be established or re-established.

There have been two broad approaches suggested to manage the impacts of the diseaseBonamiasis:

1) Selective breeding for disease resistance strains of O. angasi and the identificationand certification of disease free stocks

The French have spent many tens of millions of dollars on research to develop a Bonamiaresistant flat oyster. The large cost of developing a disease resistant Australian Flat Oystercould not be justified. However, if the Europeans are successful in producing a diseaseresistant strain of Ostrea edulis, the feasibility of technology transfer to the AustralianOstrea angasi should be explored. Likewise a molecular probe developed in France byIFREMER for Bonamia ostreae should be evaluated for use in Australia, especially as atool for screening local populations of O. angasi and associated areas for presence orabsence of the disease. Populations and associated areas found to be disease free couldthen be used to source hatchery broodstock and registered as Bonamia free therebycircumventing EU export barriers.

2) Adoption of animal husbandry procedures to promote extremely fast growth. Thisallows oysters to be marketed as large maturing juveniles before the disease candevastate fully sexually mature individuals

Industry needs to evaluate if research results summarized above can be applied on acommercial scale. The essence of the past research indicated that early production of



oyster seed in a hatchery and nursery together with mid-water growing of oysters withoutcontainers can yield marketable Flat Oysters within two years. This offers the potential to“manage around” the Bonamia problem by harvesting large juvenile oysters as theyapproach sexual maturity for the first time. It also needs to be determined if Bonamia willnow kill mature oysters every year or will be subject to periodic outbreaks.

References

Hine, P.M., 1966. New Zealand Journal of Ecology 20, 109 - 116.

Hine, P.M., 1997. Health status of commercially important molluscs in New Zealand.Surveillance 24, 25-28.

Naciri-Graven,Y., Martin, A.G., Baud, J.P., Renault, T., Gerard, A., 1998. Selecting theflat oyster Ostrea edulis (L.) for survival when infected with the parasite Bonamiaostreae. J. Exp. Mar. Biol. and Ecol 224, 1-107.

Books on the early history of oyster farming

Korringa, P., 1976a. Farming the Flat Oysters of the Genus Ostrea. Elsevier Scientificpublishing. ISBN 0-444-41334-0.

Korringa, P., 1976b. Farming the Cupped Oysters of the Genus Crassostrea. ElsevierScientific publishing ISBN 0-444-41333-2

Full titles of Reports

Hickman, N.J., O’Meley, C.M., 1988a. Culture of the Australian Flat Oyster (Ostreaangasi) in Victoria. Final Report FIRTA 84/77. Internal Report No 172.Department of Conservation Forests and Lands, Fisheries Division.

Hickman, N.J., O’Meley, C.M., 1988b. Culture of the Australian Flat Oyster (Ostreaangasi) in Victoria: Hatchery and Nursery Production. Technical Report No 68.Department of Conservation Forests and Lands, Fisheries Division.

Mantzaris, L., Hickman, N.J., Grossel, G.W., 1991. Storage and Shelf Life of theAustralian Native Flat Oyster (Ostrea angasi). Technical Report No 79. Departmentof Conservation Forests and Lands, Fisheries Division.

Reilly, D., Hickman, N.J., 1994. Development of Commercial Field Nursery and On-growing Systems for Production of the Flat Oyster (Ostrea angasi) in Open waters.Final Report to FRDC on Project DCL5Z. December 1994.

9.4. Storage and Shelf life of the Australian Native Flat Oyster (Ostrea angasi)(Mantzaris, L., Hickman N.J., and Grossel, G.W., 1991)



Abstract

The shelf life of flat oysters (Ostrea angasi) depended on storage temperature, humidityand the extent to which the oysters gaped during storage. Oysters chilled to 1.5°C bymeans of ice meltwater and weighed down by a load of 1.5 kg had a shelf life of 23 days.By contrast, oysters stored at 20°C under dry conditions and without being weighed downhad a shelf life of only 2 days. When oysters prechilled to 3°C were kept moist and tightlypacked in polystyrene boxes stored at 4.5°C, they remained fresh for 14 days but their shelflife was not prolonged by the presence of 600 g of coolant (Thermosorb or Ice-bricks).Mortality and odour were the most reliable indicators of spoilage; standard plate counts, E.coli counts, and analysis of total reducing substances were no use as indicators of spoilage.

Introduction

Because the Australian flat oyster lives subtidally, its tolerance of storage andtransportation stresses was not expected to be as high as that of intertidal rack oysters.Therefore the question of whether flat oysters could be transported long distances withoutspoilage needed to be answered. Overseas marketing of flat oysters will requiremaintenance of a high quality product for at lease one week after harvesting. Hence, inVictoria and elsewhere in Australia, there is a need to determine the best possible handlingand storage procedures which would ensure that flat oysters remained alive and of highquality during distribution and storage.

Unlike most fresh chilled seafood, oysters are distributed live because of an assumptionthat if an oyster is alive it must be good enough to eat. This assumption is dangerouslymisleading because the palatability of shellfish (detected by sensory analysis) maydeteriorate to below acceptable levels while the shellfish are still alive (Brooks and Harvey1981; Warwick 1985).

Organoleptic scores (based on odour and flavour) for mussels have been found tocorrespond with total bacteriological counts (Brooks and Harvey 1981). This suggestedthat the sensory perception of spoilage is a response to the metabolic breakdown productsformed during bacterial decomposition. Furthermore, published results from total bacterialcounts or Standard Plate Counts (SPCs) exhibited uniform, sigmoidal growth of bacteriawith storage time. Such results have led to the use of SPCs as the standard test for qualitycontrol of shellfish marketed by Australian producers.

This report describes a study in which we examined how the quality of live oysters changedin relation to the temperature and the methods used to store them. The first of three trialsconducted was designed to monitor the effects of the oysters’ orientation and storagetemperature on the oysters’ survival during dry storage. The second was designed toinvestigate the effectiveness of weighing down the oysters and the “curtain of ice” methodof chilling oysters (Boyd et al. 1978) during moist storage. In the third trial, theeffectiveness of two commercially available coolants in maintaining chilled temperatureswithin a typical shellfish packaging unit were compared. The effect of storage temperatureon oyster quality was also determined and different methods of assessing oyster qualitywere compared.



DRY STORAGE


Twelve groups of 20 oysters selected at random were cleaned of biofouling, exposed to airdry conditions at three different temperatures and four different orientations (Table 1).Storage facilities which provided the three temperatures included; a refrigerator (6±1°C), alaboratory bench at ambient temperature (20±2°C) and an oven (28±1°C). Oysters werestored on metal racks so that any shell liquor would drain away. Temperatures around theoysters were recorded at 1 hour intervals throughout the experiment using probes linked toa data logger.

Table 1. Orientation of oysters

Results and Discussion

Survival time can be regarded as an index of shelf life although useful shelf life endsbefore death. As expected, survival time increased significantly (P<0.001) with decreasingtemperature (Fig 1). Oysters survived for 11-15 days in a refrigerator at 6°C, for 6-7 dayson the laboratory bench at an ambient temperature of 20°C and for 2-4 days in an oven at28°C. Therefore at 6°C, shelf life was at least 4 days longer than that at 20°C and at least 7days longer than that at 28°C. The extent to which shelf life is reduced by continuousexposure to high temperatures emphasises the importance of keeping oysters cool at alltimes after harvesting.

An oyster closes when its adductor muscle contracts. At the same time, the hinge ligamentis compressed. Gaping follows relaxation of the adductor muscle and the elasticity of the



hinge ligament then allows the valves to separate. When gaping, the oyster loses moisturefrom its tissues and will die. When the oyster’s heavier cupped valve is upper most, gapingmay be more difficult than when the lighter flat valve is on top; hence, oysters may find itmore difficult to gape when oriented “cup up”.

Figure 1. Duration of survival (median) during dry storage of live oysters at 6°, 20° and28°C. Note: N=20 in all cases except for treatments a-d where N=16, 17, 14 and 18respectively due to the omission of individuals which failed to gape.

MOIST STORAGE

In this section we examined the effect of cooling in conjunction with weighing downoysters with a weight of about 1.5 kg.


Oysters were divided into four groups of 50 and each group was kept under differentconditions (Fig 2):

A. kept moist with tap water at ambient temperature (control);B. kept moist and weighed down with 1.5 kg at ambient temperature (pressured);C. kept under a “curtain of ice” in a cool room (chilled);D. held under a “curtain of ice” and weighed down with 1.5 kg in a cool room (pressuredand chilled).



Figure 2. Experimental treatments for moist storage of live oysters

The “curtain of ice” technique (Boyd and Wilson 1978) is a simple way of chilling oystersand keeping them damp at the same time. Ice is placed above the oysters so that the meltwater can run down around them and drain away from the bottom of the storage container.Some type of porous material is needed to separate the ice from the top layer of oysters toprevent them from freezing.

For each treatment, the oysters were oriented “cup up” and layered between pieces of jutein a bucket with a perforated base. The “cup up” orientation was used in an attempt tominimise the oysters’ tendency to gape. The buckets were placed on gratings above driptrays that collected excess water. Treatments C and D were carried out in a cool room at amean temperature of 5°C to conserve ice and to prevent it from melting completelyovernight. The unchilled treatments (A and B) were carried out at ambient temperature andthe oysters were kept moist by potable water dripping from a tap. Pressure applied withweights (treatments B and D) was a method of minimising the oysters’ gaping.


For the duration of the experiment, the ambient temperature in the laboratory varied from16.5 to 20°C with an average of 18°C. Within buckets A and B, the dampened layers ofjute brought the temperature down to 15.5°C (range 14.5-16.5°C). Under a “curtain of ice”(treatments C and D), the temperature averaged 1.5°C (range 1.0-2.5°C).

Mortality

As expected, the mortality rate of chilled oysters was lower than that of oysters at ambienttemperature (compare A with C and B with D in Fig 3). Figure 3 also shows a decrease inmortality rate associated with the application of pressure (compare A with B and C withD). This result supports our suggestion that gaping affects survival; preventing the oystersfrom gaping increases survival and could be used to advantage when oysters are beingstored.



Figure 3. Changes in mortality during moist storage of live oysters at (A) 15.5°C, (B)15.5°C and under pressure, (C) 1.5°C (D) 1.5°C under pressure. E and F are derived fromdata in the first section and represent dry storage of “cup up”- oriented oysters at 20°C andat 6°C respectively.

The tolerance of the flat oyster to very low temperatures is useful to handlers who knowthat they can safely chill oysters to near freezing temperatures to maximise shelf life.

The time taken for mortality to reach 10% was taken as a measure of useful shelf life and isreferred to here as Ts. Ten percent mortality could conceivably occur as a result of weakeroysters dying from physiological stress. At mortalities higher than 10%, bacterialdecomposition of oyster tissue becomes a more likely cause of death.

For treatments A, B, C and D, the Ts values were 6, 7, 11 and 23 days respectively(estimated from Fig 3). Therefore Ts was extended 1 day by application of pressure, 5 daysby chilling and 17 days by combining pressure and chilling. The effect of the chilling andpressure combined was therefore greater than the sum of the two effects. Weighing downthe oysters is a simple and inexpensive method for longer term storage of oysters and isapplicable to commercial operations.

Results from the dry storage treatments (Fig 3, E and F) showed that Ts was 2 days atambient temperature and 8 days in the refrigerator. Under moist conditions Ts was 6 daysat ambient temperature and 11 days when oysters were chilled. Therefore, moisture isanother factor which contributes to increased shelf life.

Boyd et al., (1980) found that Sydney rock oysters survival for no longer than 1 week at10°C in dry conditions. Pacific oysters (Crassostrea gigas) in dry storage survived for only8 days at 11°C but for 13 days under a “curtain of ice”. These results suggest that Sydneyrock oysters and Pacific oysters, although they are intertidal species, have a shelf lifesimilar to that of the subtidal flat oyster.

Bacterial Counts

Trends in the results from bacterial counts (Fig 4) differed from those of the mortality data.There was no distinct difference between bacterial counts in oysters exposed to the variousstorage conditions and the SPC limit (1 x 105 microorganisms per gram according to statepublic health legislation) was reached within about 10 days for each treatment. Because nodifferences in bacterial counts could be detected in oysters exposed to different conditionsand because bacterial growth was irregular, the SPC could not be relied on as an indicatorof quality.



Figure 4. Changes in standard plate count during moist storage of live oysters at (A)15.5°C, (B) 15.5°C and under pressure, (C) 1.5°C, and (D) 1.5°C under pressure



PACKAGED OYSTERS

Live Oyster Packaging Study

This experiment was carried out during August and September when local oysters are inbest condition (Hickman and O’Meley 1988). Clean live oysters (30 per box) prechilled to3°C were layered between dampened jute in a polystyrene box lined with a thick plasticbag at the bottom of which was placed a pad of dry Thermosorb to absorb excess liquid. Abag of water (approximately 10 L) which had also been prechilled to 3°C was placed on topof the oysters. Frozen coolant (600 g) was placed on top of the bag. Each of the boxes wassealed and the lid taped down firmly. Each box was labelled with the treatment, storagetime and date to be sampled. Temperatures within the boxes were recorded by a probeinside the bag of water. The packaging technique is shown diagrammatically in Figure 5.

Figure 5. Diagram of experimental packaging unit

Mortality

Dead oysters in each box were counted and removed so that only live oysters were used forquality assessment. The time taken for mortality to reach 10% was taken as a measure ofuseful shelf life (Ts).

Sensory Analysis

Seven people (volunteers from staff as MSL) assessed the appearance, odour, texture andflavour of the test oysters using the seven-point Smiley scale (Street and Carroll 1972). Ateach sampling, each volunteer was given eight oysters (two from each of four boxes)placed at random in eight cells labelled 1-8, on a tray.

A score of seven indicated that the characteristic being assessed was excellent. A score offour was an indication that the characteristic being assessed was beginning to go “off”. Ascore of one meant that the oyster was totally unacceptable. A mean from fourteen scoresper treatment was calculated for each characteristic. Ts was taken as the last recordingbefore the score fell below four.

If mortality was more than 10% on any sampling day the panellists would score the oysters



for appearance and odour only. As a further precaution against food poisoning, if any ofthe oysters being assessed were suspected by either the shucker or the panellist of beingspoiled, the oysters would again be scored for appearance and odour only. Thesesafeguards were strictly enforced because one oyster can cause serious illness.


Results from the various analyses showed that the presence of coolant did not increaseshelf life. Only the mortality rate data showed a slight distinction between coolants at15.5°C (Fig 6) although Ts for each treatment was similar (between 5-6 days). Therefore,the capacity for 600 g of coolant to temporarily maintain chilled temperatures was of noclear advantage to oyster shelf life. However, the use of more coolant might have produceddetectable differences between coolant treatments. Changes in mortality of packagedoysters at different storage temperatures is depicted in Figure 7.

Figure 6. Changes in mortality of packaged oysters stored at 15.5°C with differentcoolants

Figure 7. Changes in mortality of packaged oysters at different storage temperatures



Ts was calculated from the mortality and sensory data only (Table 2) because no other datashowed any spoilage pattern. An analysis of variance (Table 2) revealed a significantdifference in Ts at different temperatures. The level of significance was greater for odour(P<0.001) than for appearance or mortality (P<0.01), consequently odour was the mostsensitive indicator of oyster quality. Results from assessments of texture and flavour,although being the same as for odour, are less reliable because spoilage was assumed andnot recorded.

According to the odour index, oysters can be safely kept in the described package for 2weeks at 4.5°C before spoiling. Ts was reduced to 5 days at 15.5°C and 3 days at 24.5°Cwhich highlights the importance of maintaining a cold chain from the time oysters areharvested until they reach the consumer.

Table 2. Useful shelf life (Ts) of packaged live oysters stored under various conditions.Ts was determined by mortality and sensory analysis

Bacterial Counts

SPC (Fig 8) of bacteria in live oysters did not respond uniformly to storage temperature ortime. There was no indication of significant spoilage except at the very end of thetreatments when the counts were often very high. By this time only a few oysters hadsurvived and they would have been moribund. There was also a possibility that survivorshad been contaminated by the dead oysters decomposing around them. The SPC datatended to follow a bimodal trend which may have been due to population succession withinthe bacterial flora of the oysters. Because of this irregular growth Ts figures could not bedetermined.



Figure 8. Changes in standard plate count of packaged live oysters at different storagetemperatures

Export regulations also require the number of Escherichia coli to be determined in oystersdestined for overseas markets; the health limit for E. coli is 2.3 microorganisms per gramof tissue. In our study, the E. Coli counts never exceeded 0.2 per gram and there was noindication that the number of E. coli varied in response to storage conditions. Our resultstherefore support the view that E. coli determinations are useful only as indicators of oysterquality at the time of harvest and imply that the oysters we examined were free fromcontamination when harvested.

None of the samples tested positive for Salmonella spp.

CONCLUSIONS

These storage trials have revealed that flat oysters can be kept for three weeks under pre-packaged conditions and for two weeks in a package without spoiling. To achieve thisdegree of shelf life three key factors have been identified as being essential: continuouschilling; a moist storage environment; applying pressure to prevent oysters from gaping.All three factors influence the oysters’ useful shelf life but the main emphasis should be oncontinuous chilling. A period of unchilled storage or transport will hasten spoilage andtherefore reduce the amount of time available for the planning of product dispatch byfarmers, processors and distributors.

Our results suggest that sensory analysis (especially odour) can be used as an index of thequality of flat oysters. The main disadvantage of sensory evaluation is its subjectivity;therefore, it should be used in conjunction with an objective index. Mortality is the mostsuitable objective index; neither the microbiological nor the chemical analyses had merit asindicators of quality. Justification for the use of mortality data in conjunction with sensoryanalysis is that Ts figures for both analyses were closely correlated.



The current acceptance of bacterial counts as the standard index of oyster quality needs tobe questioned. Our results showed that bacterial counts did not increase uniformed withstorage time or respond to temperature. This inconsistent growth, along with theinconvenience of waiting for results (approximately 3 days), detracts from the importanceof describing spoilage of live oysters in terms of bacterial numbers.

RECOMMENDATIONS

Our recommendations are based on results and observations from this study and aredesigned to promote the highest possible standards to extend the shelf life of live flatoysters. If these standards are compromised, so is the time available for storage andtransport.

General Storage Conditions

The most important factor to consider when storing flat oysters is the use of effectivechilling to minimize the growth of decomposing and food poisoning bacteria.

! Oysters should be chilled to just above 0°C (0.5-2.0°C) immediately after harvest bymeans of either a high humidity chiller or a “curtain of ice”.

! During storage or transportation chilling should be continued until the product reachesthe consumer.

! Oysters should also be kept moist and weighed down to prevent gaping. This practiceextends the shelf life of the oysters to at least 2 weeks.

! Potable water should be used in all cleaning, dampening or ice making.

! During handling, mechanical shock should be kept to a minimum.

Pre-packaged Storage

Deterioration of oyster quality begins at the time of harvest. Therefore it is important toprovide chilling facilities on board the harvest vessel if shelf life is to be maximised.

! The “curtain of ice” should be used for chilling on board as it is the most cost-effectivemethod. Crushed ice should be held on board the harvest vessel for this purpose.

! Harvested oysters should be placed into drainable containers and covered with a porousmaterial which prevents the oysters from coming into direct contact with the ice butallows sufficient meltwater to run over them.

! A thick layer of ice should then be placed on top of the covering and topped up whennecessary. The ice layer should never be allowed to melt completely.

! The oysters should be weighed down in some way to minimize gaping.

! Meltwater should be allowed to drain through and away from the base of the container.



! Oysters should be cleaned thoroughly and any fouling organisms removed.

! Onshore, oysters should be stored in a high-humidity chiller or under a “curtain of ice”.

Packaging

Oysters should be packaged and dispatched as soon as possible after harvesting becausealthough chilling slows down spoilage it does not stop it altogether.

! Oysters should be packed at a temperature not exceeding 3°C and so may requireprechilling by dipping the oysters in an ice slurry for 2-3 seconds.

! Oysters should be packed quickly so that they remain chilled.

! Refrigeration should not be relied on to bring the temperature of packaged oystersdown to chilled temperatures. The insulating effects of the packaging will retardcooling.

! Polystyrene boxes are extremely effective containers for maintaining chilled conditions.Alternative containers which could be used include lined and wax-impregnatedcardboard boxes or stackable double-walled plastic boxes which could be returnedrelatively cheaply to the processors.

! More “high tech” packaging systems specifically developed for heat-sensitive seafoodproducts are also available (Anon. 1989, 1990). Whatever the choice, the containermust be sturdy, leakproof and thermally insulated.

! An absorbant pad (Thermosorb is recommended) should be placed beneath the oystersto absorb excess liquid.

! Oysters should be layered into the container. The material used to separate layersshould be dampened to maintain high humidity within the package and should alsoprovide cushioning to prevent shell damage.

! The container should be filled to a point where the lid has to be forced down to shut thecontainer. This will ensure that the oysters are packed under pressure. The lid shouldbe lined with some type of compressible material (e.g. “bubble wrap”) to stop thecontents from moving.

! The package should be thoroughly sealed and bound to prevent leakage and to maintainpressure.

! Packaged containers awaiting despatch should be kept in cool storage.

Transport

Temperature histories during the distribution of live oysters will vary depending on theseason and destination of the consignment.



! The handling of containers should be scheduled so that the packages are not exposed toambient temperatures for longer than is absolutely necessary.

! For road transport, a refrigerated vehicle is necessary to maintain chilled temperatureswithin the packages.

! During air freighting, temperatures down to 8°C can be maintained in the cargo holdwhile the plane is in flight but during loading, unloading and stop-overs, packages maybe left unrefrigerated for long periods of time. Maintaining a cold chain is mostdifficult during air-freighting.

! The addition of a coolant is recommended for packages that are to be air freighted. Acoolant will slow down the rate at which the oysters warm up but the duration of thecoolant’s effectiveness will depend on the amount of coolant used and the externaltemperature.



10. MARKETING SCOPE FOR FLAT OYSTERS IN NSW,INTERSTATE AND OVERSEAS

Nick Ruello, (Ruello and Associates), Martin Palmer (Martin Palmer Seafoods), MarkEather (Jolly Roger Exports)

compiled by

Mike HeasmanNSW Fisheries, Port Stephens Fisheries Centre


The following is an account of practical experience gained from marketing of farmed flatoysters in NSW since 1999. It is based primarily on notes compiled from non-scriptedtalks at the workshop given by local seafood processing and marketing experts Mr NickRuello (Ruello and Associates) and Mr Martin Palmer (Martin Palmer Seafoods). It alsoincludes comments provided by a third seafood marketer, processor and exporter Mr MarkEather (Jolly Roger Seafood Exports) following his return from Asia in mid March 1999and by several oyster farmers involved in pilot flat oyster farming over the past three years.Those south coast farmers providing additional marketing comments included Chris andShelley Boyton from Pambula, John Smith from Bermagui and David Maidment fromDalmey.

Both Nick Ruello and Martin Palmer stressed the need by the NSW oyster growersinvolved in pilot production of flat oysters industry to abandon the assumption that theirjob ended at the farm gate i.e. that seafood marketers would assume all responsibilities andcosts of developing local interstate and export markets for new products and also promotethe product.

To the contrary, producers must be prepared to invest their time and hard earned cash intomarket research development if they are genuinely serious about diversifying productionaway from Sydney rock oysters into distinctly different products such as flat oysters thatwere both new and unfamiliar to local and interstate consumers. Likewise they must alsobe prepared in the longer term to bear the major cost and responsibility of developingexport markets if and when volume and consistency of production reached levels that couldto justify costs of overcoming some serious hurdles to profitable export.

Critical elements of market research and development identified by outlined by NickRuello and Martin Palmer were as follows:

1. A need to define flat oysters relative to other sea-foods in general and to other bivalvesspecifically (especially other species oysters including Sydney rock and Pacificoysters). On this point Nick Ruello stated that results of a very large survey he hadconducted on Australia consumers had revealed that raw oysters were highly esteemed,recognised at the top end of the seeafood range and were considered (along withAtlantic salmon), trendy. Of consumers interviewed, 99% had heard of oysters and of



these were found to either adore (about 52% of the population) or detest (about 23%)raw oysters. The remaining 25% of consumers had not tried raw oysters nor could bepersuaded to do so. Mr Ruello also remarked that the `urban myth’ that oysters are anaphrodisiac is a beneficial marketing tool.

2. There is a need to have flat oysters recognised as distinctly different and a moreexotic/sophisticated product than Sydney rock oysters. There is a strong loyalty inNSW to the Sydney rock oyster which are traditionally sold a dozen to a plate. MartinPalmer and Nick Ruello concurred that the natural advantages of flat oysters over rockoysters such as a more attractive rich green colour, more rounded and uniform cupshape, a higher suitability for cooking and the flat oyster’s glamorous French (Belon)connection, favoured a small price margin of around $1/dozen over rock oysters. Theyalso agreed that young, generally more adventurous clientele should be the primarytarget of market promotion and that an attractive and trendy name such as Angasi,Belon or Australian Flat oyster be universally adopted. Another potential marketattribute discussed was the possible use of a 25 to 30 mm white medallion on the uppershell of flat oysters to carry a quality brand or sticker. Grading standards and protocolsfor packing need to be adopted with a focus on shelf life.

3. Serious concern was expressed by Martin Palmer and Nick Ruello at the ad hoc natureof market supply to date and of flesh quality that has varied from excellent to very poor.These concerns highlight the need of strict monitoring of seasonal variations in fleshquality. There is a need to develop and apply minimum flesh quality standards and toset harvest size at an optimum shell height of 70 to 80 mm (80g). Both marketersraised the issue of flat oysters being harder to open than Sydney rock oysters. It wasidentified there was a need to educate chefs and shuckers who are used to closedoysters (50% of restaurants now buy closed oysters).

4. Problems of variable flesh quality have been exacerbated by the common presence ofgrey-sick and black-sick brooders and by the gaping behavior of healthy flat-oystersmistakenly taken as evidence of actual or impending death. Neil Hickman drewattention to the need to apply optimum wet and dry handling, packing and chilledstorage protocols developed by MAFRI in Victoria that prevent gaping and extend shelflife of live flat oyster from 2 to 3 days to 7 to 10 days (see Section 9.4 of Hickman, thispublication).

5. Another very important issue of quality raised by David Maidment, was that the need tominimise risks to consumers from infectious bacterial and viral diseases and algae bio-toxins . The take home message was that the current overhaul of the NSW ShellfishQuality Assurance Program be extended and adapted to cater for flat oysters.

6. Critical additional issues associated with export of flat oysters was the need toestablish:

! a marketing strategy to identify the flat oyster as a premium quality Australian nativeoyster, grown in clean-green environment;

! an accredited Quality Assurance Programs to meet various minimum specifications setby the United States Food and Drug Authority, the European Union and equivalentgovernmental agencies in Hongkong, Singapore and China;



! specific pathogen free status for live exports in relation to Bonamia.



11. SWOT ANALYSIS FOR DEVELOPMENT OF FLATOYSTER OSTREA ANGASI FARMING IN NSW



This analysis incorporates important issues raised prior to, during and subsequent to theworkshop.

STRENGTHS

Production attributes

! Relatively short turn-off time (18 to 24 months) especially when compared to Sydneyrock oysters (36 to 48 months).

! Potential to capitalize on the large and diverse array of expertise, infrastructure andequipment, associated with production, distribution and marketing of rock oysters inNSW.

! A relatively high tolerance to major short to medium term falls in salinity as exhibitedby all but the smallest spat during pilot farming operations. (Accordingly the scope forSydney rock oysters (SRO’s) farmers to diversify into flat oyster production is widerthan previously projected on the basis of experimental investigation of salinitytolerance).

! Some (albeit limited) existing commercial production experience flowing from three yearsof trial farming by SRO farmers in Southern and central coast estuaries.

! Successful commercial scale hatchery and nursery production demonstrated over the pastthree years. This is in stark contrast to SRO that have proven a highly problematic speciesfor hatchery/nursery production over the past 15 years.

! Protracted seasonal availability of brooders (natural breeding season now known toextend from at least June to December on the far south coast of NSW.)

! Higher apparent natural resistance of flat oysters than rock oysters to over-catch andother forms of bio-fouling and mud worm infestation.

! Opportunities for sub-tidal culture (longlines, rafts/pontoons).

Marketing attributes

! A substantially higher local market price expectation ($6.50 /doz.) for flat oysters thanfor SRO’s ($4 to 5/doz.)

! More popular than rock oysters for Asian style cooking (banquet jumbos) and inbreaded form.

! Very attractive appearance (superior shell shape, texture and color than rock oysters).This attribute will aid development and promotion of new and expanded local andinterstate “angasi” markets.

! Presence of a smooth 2 to 3 cm diameter medallion of off-white shell on the upper(right ) flat valve that could carry a promotional logo or brand.



! Flat oysters, unlike rock oysters, do not attract a 17.5% tariff loading into the EuropeanUnion (EU) countries.

WEAKNESSES

Production difficulties

! Uncertainty surrounding continuity and reliability of seed supply. Apart from thebivalve hatchery at PSFC, only one very recently established private commercialhatchery (Pisces P/L) at Brooms Head in northern NSW has the capacity and intentionto produce seed oysters.

! Most estuaries and bays in NSW untested in the production of Flat oysters.! Limited availability of suitable farming sites (higher salinity subtidal areas within

sheltered bays and estuaries) in NSW than for SRO’s.! Greater exposure of subtidally farmed oysters to predation by fish, gastropods

flatworms, crabs etc. and to biofouling and mud worm infestation.! Relative ignorance of market quality factors for flat oysters and seasonal/site

fluctuations thereof.! Potential difficulties in complying with minimum safe food standards being applied by

the European Union countries the USA and China.! Potential difficulties in complying with Bonamia disease free certification standards

being applied by the European Union countries and the USA under internationalstandards set by the Office Internationales Epizooies (OIE).

! Apparent short seasonal availability of flat oysters in “fat” (pre-spawning) condition.! Impact of acid sulphate soil run-off in some northern estuaries.! Lack of venture capital available to SRO oyster farms to diversify into new products

and productions techniques. This is due to the continuing 25 year decline in theindustry.

Marketing Difficulties

! Very unattractive appearance and texture of flat oysters in grey-sick and black-sickbrooding condition.

! Significantly different (flintier) taste and coarser texture of Flat oysters relative to rockoysters.

! In NSW there is an entrenched loyalty of many consumers for the “traditional SRO”reinforced by general lack of local consumer awareness of this alternative native oyster.

! Normal gaping behaviour of unrestrained flat oysters is usually mistaken as evidence ofactual or impending death.

! Probable shorter market season than SRO.! The NSW oyster industry’s lack of a centralized marketing and promotional arm to

establish and enforce universal quality standards.! Continuing pollution and associated public health risk issues associated with estuarine

production of oysters in NSW, e.g. recent Wallis Lake hepatitis B and toxic algaeincidents.

! Flat oysters are considerably more difficult and hence costly to open than rock oysters.



OPPORTUNITIES

Production

! Production of faster growing (up to 60%) triploid flat oysters utilizing expertise that hasbeen developed for routine hatchery production of triploid SRO’s at PSFC.

! Bonamia has not yet recorded in NSW O. angasi and may be able to be avoided usingrack and suspended farming methods as already demonstrated by Marine andFreshwater Research Institute in Port Phillip Bay, Victoria.

! Increased incorporation of flat oysters into current anti-fouling research anddevelopment being developed primarily for SROs and pearl oysters.

Marketing

! There is a major global shortfall in supply of flat oysters due primarily to Bonamiadevastation of natural and seeded beds. This will ensure continuing high price exportmarkets for good quality flat oysters.

! Development and implementation of Specific Pathogen Free certification programsmeeting all requisite specifications set by the OIE. Growing areas and the oystersthemselves will need to be surveyed for a minimum of two years and found to beBonamia free in accordance with OIE guidelines. Export flat oysters will also need tocomply with health safeguards for consumers through compliance with QualityAssurance Programs set b the Australian Shellfish Safety Control Program, the EU, andthe United States Food and Drug Authority.

! Major extension of the shelf-life of live flat oysters from periods of 2 to 3 days up toperiods of at least 2 weeks can be achieved if optimal packaging and chill storagetechniques originally developed by MAFRI, in Victoria are implemented.

! Scope exists for 2 to 3 year old “jumbo flat oysters” to be exported into a traditionalhigh price ($10-15/doz.) markets in China and Western Europe or to cater for touristsfrom these countries.

! Salvaging of brooder flat oysters in otherwise non-marketable grey-sick and black-sickcondition can be achieved by simply flushing away of larvae prior to serving raw orcooking.

! Use of natural gaping behavior of flat oysters as an aid to opening them.! Marketing production into “out-of-season” markets in the northern hemisphere or other

traditional flat oyster markets (e.g. French Polynesia and New Zealand).



THREATS

! Inability to achieve Bonamia-free certification of flat oysters.! Lack of continuity of supply of seed if hatchery output at PSFC is curtailed or

downgraded or if commercial hatcheries do not come on-line.! Possible genetic inbreeding unless large numbers of brooders (50 to 100) originally

collected from the wild are periodically acquired and used as a source of hatchery seed.! Current moratorium on new oyster farming leases that may be well suited to O. angasi

production including optimal sites in Jervis Bay and Twofold Bay.! Threats to consumer health posed by bacteria (including endemic species of Vibrio and

human enteric bacteria) viruses (especially hepatitis A and Norwalk), and toxic algaeblooms (especially oceanic blooms impacting on deeper higher salinity farming sites).

Fisheries Research Report Series: No. 6, Page 55

12. DELEGATES AND ABSENTEE CONTRIBUTORS

Address 1 Address 2 Telephone Fax Email addressAboriginal Community RepresentativesAndrew Harvey Jerringja Aboriginal

CommunityHawken Rd Tomerong NSW 2540 02 4443 4985 02 4443 4985

Guest Researchers/AdvisorsDr Rob Adlard Queensland Museum Brisbane 07 38407723 [email protected] Rocky De Nys Centre for Marine Biofouling

and Bio-Innovation,University of New South Wales 02 9385 1584 [email protected]

Sophie McCloy Centre for Marine Biofoulingand Bio-Innovation,

University of New South Wales 02 9385 1584 [email protected]

Neil Hickman Victorian Dept of NaturalResources & Environment

Marine and Freshwater ResourcesInstitute, Queenscliff, Victoria.

03 5258 0336 [email protected]

NSW Fisheries StaffLaurie Derwent Fisheries Research Institute Nicholson Pde., 202 Cronulla, NSW 2230 02 95278411 02 95278576 [email protected] Diemar Port Stephens Fisheries

CentrePvte Bag 1 Nelson Bay, NSW 2315 02 4982 1232 02 4982 1107

Dr Rick Fletcher Fisheries Research Institute Nicholson Pde., 202 Cronulla, NSW 2230 02 95278411 02 95278513 [email protected] Goard Port Stephens Fisheries

CentrePvte Bag 1 Nelson Bay, NSW 2315 02 4982 1232 02 4982 1107

Dr Mike Heasman Port Stephens FisheriesCentre

Pvte Bag 1 Nelson Bay, NSW 2315 02 4982 1232 02 4982 1107 [email protected]

Ian Lyall Port Stephens FisheriesCentre


Steve McOrrie Port Stephens FisheriesCentre


Dr John Nell Port Stephens FisheriesCentre


Damian Ogburn Port Stephens FisheriesCentre


Bill Rutledge Port Stephens FisheriesCentre


Melissa Walker Port Stephens FisheriesCentre

Pvte Bag 1 Nelson Bay, NSW 2315 02 4982 1232 02 4982 1107

Fisheries Research Report Series: No. 6, Page 56

Delegates and Absentee Contributors cont’d

MarketersNicola McConnell Sydney Fish Markets Pyrmont, Sydney NSW [email protected] Eather Jolly Roger Exports 15 Manna Ave Figtree Heights 2525 02 4268 1115 02 4268 1104 Jolly [email protected] Ruello Ruello and Associates,

Seafood Consultants4 Sherwin St. Henley, NSW 2111 02 9817 4652 02 9879 6501 [email protected]

Martin Palmer Martin Palmer Seafoods PO Box 94, Edgecliff, NSW 2027 02 9818 6998 02 9818 6960Stefin Pascalidis 19 Wallaringa Street Batemans Bay NSW 2536 044 726 403

NSW Dept.State and Regional DevelopmentPaul Clancy DSRD p.o. Box N808, Grosvenor Place

NSW 122002 9338 6664 02 9338 6676

NSW Oyster Farmers Association RepresentativesRoger Clarke President , NSW Oyster

Farmers AssociationPO Box 244, Turramurra, NSW2074

029487 3566 02 9487 1849 [email protected]

NSW Oyster FarmersRay Tynan Shed 5, Landing Road Pambula Lake 02 6495 6398 02 6495 6395Laurie Lardner Holiday Coast Oysters PO Box 456, Port Macquarie, NSW,

244402 6584 2220 02 6584 2464 [email protected]

Jim Croucher Po Box 252 Narooma, NSW 2546 4476 2655Ross Wiggins 7 Lincoln Cres Batemans Bay NSW 2536 044 727 565Stefin Pascalidis 19 Wallaringa Street Batemans Bay NSW 2536 044 726 403Chris and ShelleyBoyton

P.O. Box 365 Pambula NSW 2549 064 956 988

Frank van Eden P.O. Box 407 Woy Woy NSW 2256 043 423 796 02 64 95 6605Richard Roberts Talinga Pty Ltd, 13

Harbour DrBroulee NSW 2537 044 716 004 02 44 76 3322

Mick Horton 3 Munje Street Pambula NSW 2549 064 956 440 02 44 71 6857Peter Bachelor 91 Hanlan St Narara, NSW 2250David Maidment 11 Maculata Circuit Dalmeny NSW 2546 044 738 017(w)

John Smith 6 River Road Bermagui NSW 2546 064 934 000 02 6493 4000Stephen Feletti 3 Garagarang St Malua Bay, NSW 2536 02 4471 1018

OthersJohn Hedison Silver Beach

Aquaculture88 Wyralla Rd, Yowie Bay 2228 02 9525 1115 02 9524 1727

Other titles in this series:

ISSN 1442-0147

No. 1 Otway, N.M. and Parker, P.C., 1999. A review of the biology and ecology of thegrey nurse shark (Carcharias taurus) Rafinesque 1810.

No. 2 Graham, K.J., 1999. Trawl fish length-weight relationships from data collectedduring FRV Kapala surveys.

No. 3 Steffe, A.S., Chapman, D.J. and Murphy, J.J., 1999. A description of the charterfishing boat industry operating in the coastal and estuarine waters of New SouthWales during 1997-98.

No. 4 Reid, D.D. and Smith, I.R., 1998. The 1998 Pacific oyster survey.

No. 5 Walford, T. and Pease, B., 2000. Strategies and techniques for sampling adultanguillid eels. Proceedings of a workshop held at FRI, Cronulla, Australia,August 1999.

No. 6 Heasman, M. and Lyall, I., 2000. Proceedings of the workshop held on 3 March2000 at the Sydney Fish Markets: Problems of producing and marketing the flatoyster Ostrea angasi in NSW.

Documents

Fisheries Research Report Series - NSW Department of ... · Fisheries Research Report Series: ... Culture of the Australian Flat Oyster ... SWOT ANALYSIS FOR DEVELOPMENT OF FLAT OYSTER