56433604 Redclaw Crayfish Aquaculture

8/18/2019 56433604 Redclaw Crayfish Aquaculture

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Redclaw Crayfish

Aquaculture

Edited by CM Jones


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C.M. Jones (editor)

Recommended Practices for Redclaw CrayfishAquaculture based on Research andDevelopment Activities, 1988 through 2000.

Northern Fisheries Centre,Department of Primary Industries and FisheriesCairns Q 4870, Australia

[email protected]

mailto:[email protected]:[email protected]


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PREFACE

Interest in the aquaculture of redclaw crayfish has continued to be strong since initialassessments of this species were made in the late 1980's, through both Industry trials

and Department of Primary Industries and Fisheries research. Considerable Industrydevelopment has occurred since that time, although with limited success. Unlike thedevelopment of most other Australian aquaculture industries for which existingtechnologies established elsewhere have been transferred, redclaw aquaculture hasdeveloped independently. This is primarily because existing crayfish aquaculturetechnologies are not suitable for redclaw. In virtually every aspect of the productiontechnology for redclaw, there have been no established procedures or standards. It isthe development and definition of these procedures and standards which constitutedthe broad goal of redclaw research activities at the Freshwater Fisheries andAquaculture Centre, Walkamin, through to 2000.

This work has been financially supported by the Fisheries Research and DevelopmentCorporation (FRDC), the Australian Centre for International Agricultural Research(ACIAR), and Queensland Department of Primary Industries and Fisheries who haveall contributed to the research program. An integral part of this program is the transferof information and technology to industry. This has been achieved through a varietyof means, the most direct being the presentation of seminars. This publicationrepresents background notes for these seminars as they were presented through thelate 1990’s.

I would like to acknowledge all those who made contributions which led to the

preparation of this publication. Jo Grady (DPI&F Walkamin) and Greg Love (crayfishfarmer) provided presentations at the seminar. Thanks also to Peter Long, MillinCurtis, Ian Ross, Colin Bendall, Andrew Hinton and Maurice Downing (all of theDPI&F&F) who provided information and /or assistance with the preparation of thenotes.

Clive Jones


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CONTENTS

PREFACE ............................................................. .................................................................. ................ III CONTENTS ............................................................. ............................................................... ................IV

FIGURES .............................................................. .................................................................. ................VI TABLES................................................................................... ............................................................... VI A SITE ASSESSMENT FOR SUITABILITY OF FARMING REDCLAW ............................................ 1

Summary ....................................................... ................................................................ ....................... 1 Location and Services...................... ...................................................................... .............................. 1 Climate and Water Quality ............................................................... ................................................... 1 Soil Types............................................... ..................................................................... ......................... 2

Alternative Crops................................... ..................................................................... ......................... 3 Water Resources Comment..................... ..................................................................... ........................ 3 Charleville Redclaw Farm................... ..................................................................... ........................... 3

Local Issues ................................................................................ ......................................................... 4 INTRODUCTION TO REDCLAW ................................................................. ........................................ 6

Introduction ................................................................... ................................................................ ...... 6 Historical Perspective ........................................................................................................ ................. 6 Biological Characteristics ............................................................... .................................................... 7 Feeding Characteristics....................................................................................... ................................ 8 Growth Rate.............................. ..................................................................... ...................................... 8

Reproduction ............................................................................ ........................................................... 9 Life Cycle..................................................................... .................................................................. ...... 9 Disease and Parasites .............................................................................. ......................................... 10 Farming Technology...................................................... .............................................................. ...... 10 Summary ....................................................... ................................................................ ..................... 10

SITE REQUIREMENTS .................................................................... .................................................... 12 Site Requirements ..................................................................... ......................................................... 12 Site Suitability Criteria ................................................................................................. ..................... 12

POND AND CONSTRUCTION ENGINEERING ISSUES ............................................................. ..... 15 Water Supply................................................................. ................................................................ ..... 15 Construction Materials ................................................................. ..................................................... 15 Pond Design ................................................................ ................................................................ ...... 15 Pond Details ................................................................. ................................................................ ..... 16

Lining Materials ............................................................. ................................................................... 16 Basic steps in Pond Construction .................................................................... .................................. 17

PRODUCTION TECHNIQUES FOR REDCLAW .............................................................. ................. 18 Introduction ................................................................... .............................................................. ...... 18 Farm Layout Considerations.................................................................... ......................................... 19

Juvenile Supply .................................................................... .............................................................. 19 Stock Management................................ ................................................................ ............................. 21

Harvesting ......................................................................................... ................................................ 22

Feeding ............................................................... ............................................................... ................ 22 Pond Management....................................................... ................................................................. ..... 23 Outcome.................. ................................................................ ........................................................... 24

FARM MANAGEMENT .............................................................. ......................................................... 26 1. Your Objective ................................................................ ............................................................... 26 2. Recognising the Processes........................................................ ..................................................... 26 3. Developing the Strategy............................................. .................................................................... 26 4. Allocating Resources ....................................................... .............................................................. 28 5. Setting Timetables................................................... .................................................................. ..... 28 6. Identifying Assessment Criteria and Standards.......... ................................................................... 29 7. Assessing Performance........................................................................ .......................................... 29 Conclusion .................................................................... ............................................................... ...... 30

WATER QUALITY ............................................................ ............................................................... .... 31

Pond Preparation ................................................................ .............................................................. 31 Managing plankton....................................................... ............................................................... ...... 34


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Pond dynamics.......................................... ............................................................... .......................... 35 Record K eeping .................................................................. ............................................................... 38

REDCLAW ECONOMICS.................................................................... ................................................ 39 Summary ....................................................... ................................................................ ..................... 39

Introduction ................................................................... .............................................................. ...... 40 Results...................................... ..................................................................... ..................................... 40

Sensitivity analysis...................... ..................................................................... .................................. 48 Provision of Initial Stock ......................................................... .......................................................... 50

INDUSTRY OVERVIEW (1994) .................................................. ........................................................ 54 REDCLAW MARKETING .............................................................. ..................................................... 56

Introduction ................................................................... .............................................................. ...... 56 Overseas Markets ........................................................... ................................................................... 56

Domestic Market................................................... ....................................................................... ...... 58 Product Issues.......................................................................... .......................................................... 58 Pricing & Its Implications ................................................................ ................................................. 60 Promotion ....................................................... .................................................................... ............... 60 Summary ....................................................... ................................................................ ..................... 60


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FIGURES

FIGURE 1. DIAGRAM OF REDCLAW LIFE CYCLE. ............................................................. ............................ 9 FIGURE 2. LAYOUT OF A HYPOTHETICAL REDCLAW FARM CONSISTING OF FORTY 1,000M2 PRODUCTION

PONDS......................................................................................................................... ...................19 FIGURE 3. ESTIMATING AGRICULTURAL LIME APPLICATION RATE. (MODIFIED FROM BOYD, 1990). ........ 33 FIGURE 4. TYPICAL CHANGES IN PLANKTON DENSITY AFTER POND FILLING IN WELL MANAGED PONDS. . 3 4 FIGURE 5. TYPICAL WATER TEMPERATURES OVER 24 HOURS IN A REDCLAW POND IN NORTH

QUEENSLAND DURING SUMMER . ................................................................ .................................... 35 FIGURE 6. TYPICAL PH LEVELS OVER 24 HOURS IN A REDCLAW POND IN NORTH QUEENSLAND. LEVELS

ARE GIVEN FOR LOW ALKALINITY (50PPM) WATER .................. 36 FIGURE 7. TYPICAL DISSOLVED OXYGEN LEVELS OVER 24 HOURS IN A REDCLAW POND IN NORTH

QUEENSLAND. ........................................................... ................................................................ .... 37 FIGURE 8. ACCUMULATIVE CASH FLOW OVER TIME FOR A MODEL REDCLAW FARM WITH 53 X 750M2

PONDS....................................................................................................................................... ..... 51 FIGURE 9. PERCENTAGE BREAKDOWN ON OVERHEADS FOR MODEL REDCLAW FARM WITH 53 X 750M2

PONDS. ............................................................ ................................................................ ............... 52 FIGURE 10. PRICE AND RETURN TO CAPITAL AND MANAGEMENT FOR A MODEL REDCLAW FARM WITH 53 X

750M2 PONDS. ............................................................ ............................................................... ..... 52 FIGURE 11. TOTAL POND AREA VERSUS RETURN TO CAPITAL AND MANAGEMENT FOR A MODEL REDCLAW

FARM WITH 53 X 750M2 PONDS. ....................................................... .............................................. 53

TABLES

TABLE 1. ESTIMATED WATER TEMPERATURES FOR AQUACULTURE PONDS AT CUNNAMULLA. .................. 2 TABLE 2. PREFERRED RANGE OF SELECTED WATER QUALITY PARAMETERS OF SOURCE WATER , FOR

REDCLAW AQUACULTURE. .............................................................. ............................................... 13 TABLE 3. WATER QUALITY PARAMETERS, THEIR PREFERRED RANGE AND MEASUREMENT FOR REDCLAW

AQUACULTURE.............................................................................................. ................................. 24 TABLE 4. LIMING AND NON-LIMING COMPOUNDS USED FOR AQUACULTURE PONDS. ...............................31 TABLE 5. ESTIMATED FEED COSTS FOR A MODEL REDCLAW FARM WITH 53 X 750M2 PONDS................... 41 TABLE 6. ALLOCATION AND COSTS OF HIRED LABOUR FOR REDCLAW FARMS OF VARYING SIZE.............. 42 TABLE 7. TOTAL CAPITAL COSTS FOR A MODEL REDCLAW FARM WITH 53 X 750M2 PONDS...................... 43 TABLE 8. DISCOUNTED CASH FLOW FOR MODEL REDCLAW FARM WITH 53 X 750M2 PONDS WITH POND

LINERS. ........................................................... ................................................................ ............... 45 TABLE 9. DISCOUNTED CASH FLOW FOR MODEL REDCLAW FARM WITH 53 X 750M2 PONDS WITHOUT POND

LINERS. ........................................................... ................................................................ ............... 46 TABLE 10. SUMMARY OF ECONOMIC ANALYSIS FOR A MODEL REDCLAW FARM WITH 53 X 750M2 PONDS,

USING A FARM-GATE PRICE OF $10.00/KG. ........................................................... .......................... 47 TABLE 11. VARIATIONS IN FARM-GATE PRICE ON RETURN TO MANAGEMENT FOR A MODEL REDCLAW

FARM WITH 53 X 750M2

PONDS. ....................................................... .............................................. 48 TABLE 12. VARIATIONS IN REDCLAW YIELDS ON RETURN TO MANAGEMENT FOR A MODEL REDCLAWFARM WITH 53 X 750M2 PONDS. ....................................................... .............................................. 49

TABLE 13. COST OF PRODUCTION AND RETURN TO MANAGEMENT FOR REDCLAW AQUACULTURE WITH

VARIOUS TOTAL POND AREA. .......................................................... ............................................... 50 TABLE 14. COST AND POND ALLOCATION FOR STOCKING A MODEL REDCLAW FARM WITH 53 X 750M2

PONDS. ............................................................ ................................................................ ............... 51


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REDCLAW CRAYFISH AQUACULTURE 1

A SITE ASSESSMENT FOR SUITABILITY OF FARMINGREDCLAW

Peter Long

Summary

In July 1994, a preliminary assessment of redclaw production in South-WestQueensland was undertaken.

Information was gathered on environmental conditions, soil characteristics, localservices available, land-holder interest, government agency comments, Paroo Shiresupport and existing redclaw production experiences. Five interested land-holders

were interviewed at length, which provided a fruitful exchange of ideas and concepts.The Paroo Shire Council representatives certainly provided a positive hearing and one producer of 18 months experience (Charleville) provided some insights into his local production experiences.

Location and Services

Cunnamulla (population 1700) is located some 807km from Brisbane and 197kmfrom Charleville (population 3500), the closest major town. The community isserviced by aircraft twice a week, rail twice a week and bus three times a week.

The office of the Paroo Shire is headquartered in Cunnamulla and ongoing support forthe project has been provided by both Suzette Beresford, Shire Chief ExecutiveOfficer and Paroo Shire Chairman, Darby Land.

Cunnamulla is located on the Warrego River (Murray-Darling Catchment). TheCunnamulla Weir, adjacent to the town was completed in 1992 and provides anannual yield of in excess of 3000Ml with a 92% reliability factor.

Climate and Water Quality

The annual rainfall of the district ranges from 300 to 350mm (November-March) andCunnamulla's altitude is 189 metres. The net evaporation rate (Cunnamulla Post

Office) is 2.55m a year. Mean maximum daily temperatures range from 18.9°C in

July to 35.6°C in January with minimums of 5.5°C in July to 25.4°C in January.Using the pond temperature model (Australian Fisheries, November 1990), based on

ponds at Walkamin Research Station, the following pond water temperatures could be predicted at Cunnamulla.


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2 REDCLAW CRAYFISH AQUACULTURE

Table 1. Estimated water temperatures for aquaculture ponds at Cunnamulla.

Month Pond temp. (°C) Max. Pond Bottom Temp.

(°C)

JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctober

NovemberDecember

31.529.526.820.614.311.310.213.117.022.0

25.527.5

34.532.528.824.619.316.315.217.121.025.5

29.530.5

As quoted previously, 2600Ml is available for allocation from the Cunnamulla Weir.Water Resources are at present finalising allocations. Several land holders adjacent tothe weir hold 30-100Ml annual allocations, some of which is used to irrigate pasturecrops. The bulk of the water allocation is in one parcel, and will be used to irrigateeither cotton or table grape production, depending on the successful applicant. TheCouncil has requested an E.I.A., if cotton production is to proceed, and there is a

degree of unease with this crop's production in the district. Water Resources havewithheld 300Ml of allocation for future Council use and additions to presentallocations of small licence holders.

Both artesian and sub-artesian waters are available in the region, the quality of whichvaries. The majority of South-West Queensland sits over the Great Artesian Basin(G.A.B.), this water supply has traditionally provided stock and domestic suppliesthroughout the region.

Three conductivity reports sighted ranged from 700 to 4000 uS/cm with a pH in therange of 7.8 to 8.5. In general most artesian water around Cunnamulla is regarded as

drinkable and of good quality, (unscientific, but some measure of quality is reflected).Volumes from bores were quoted up to 1.3Ml per day and the water pressure does notvary.

Soil Types

A preliminary assessment of the soil types divides the district into 3 "simple"categories - black (heavy clays), red (light clays) and river loams. Drawing on the

property dam construction experience, there appears to be few problems with blackand red soils, but comments about the river loams would suggest potential difficulties.Sand and gravel run through the soil profile in some of the flood plain areas.


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Alternative Crops

South-West Queensland by and large is considered to have a depressed rural incomedue, to a greater part, to depressed wool prices. Both the state and Commonwealth

Governments are supporting a "Mulga Land Strategy" to underpin the region withincome support, property rationalisation and investigations of alternative productionsystems. As discussed previously, cotton and table grape production are seriouscandidates along with garlic and native plant production. The first three requireirrigation, and would, in the case of Cunnamulla, be limited by water allocations fromthe weir. Artesian water is unsuitable for sustained irrigation usage. There was also asuggestion of limited expansion of pasture crop production, again based on the weirwater allocations.

Water Resources Comment

Mr Lachlan Hanley, Water Resources Engineer, Charleville, was consulted and provided the following observations. There are three water sources in this region -surface (Cunnamulla Weir), sub-artesian and artesian (G.A.B.) As previouslydiscussed the allocation of water from the weir is at present in the final stages ofnegotiation and is committed, with flood harvesting of the Warrego committed for atleast 2 years. Possible flood harvesting requires off-stream storage and can beunreliable in this region. The present weir allocations have a 92% reliability.

Water of the G.A.B. flows at different rates depending on the bore and vary in qualitythrough the region. (A Water Resources survey of G.A.B. water quality of the

Warrego region is available). Bores presently provide for domestic and stock purposes. If the water was to be used for aquaculture a permit would need to beapplied for along with a $55.00 application charge. Water usage from the G.A.B. is

becoming increasingly sensitive, a bore capping program is under way andGovernment support for pipe replacement of bore drains is under way. There is anational program to reduce usage of these waters. Historically a lot of artesian waterhas run to waste, down bore drains. Lachlan advised to apply for a reasonable G.B.A.allocation for aquaculture as allocations are made with the "bigger picture" of thewhole basin in mind.

Sub-artesian water is available in areas and is not subject to the same process of

approval, a decision can be made at the district office based on the local water tableand demand levels.

Charleville Redclaw Farm

Mr Roy Bignell is at present experimenting with seven ponds on the outskirts ofCharleville. He is using both artesian and sub-artesian waters. The sub-artesian waterhas a conductivity of 3000-4000 with the artesian water around 1000-1200. He hasdeveloped the technique of blending the waters. Reasonable "blooms" were observedin several on the ponds and he claimed the crayfish, first stocked in February 1993

were doing very well and reproducing at a good rate.


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No pond bottom drains were installed and I would suggest he had some pond bottom problems. Crayfish were observed with tail blisters and tail sections missing in some ponds. Chook pellets were used and small juveniles were noted at the time of visit.

This redclaw farm illustrated to me the possibility of redclaw production in G.A.B.waters. Pond management may need to be modified to produce good blooms and thus

provide a good pond environment.

Local Issues

The Cunnamulla district is within the "channel country" and as such is relatively flat,floods spread out from the major streams/Warrego and Paroo Rivers and cover largetracts of country. Both from economic loss and permit requirement considerations, all

ponds need to be above flood height. This issue would need to be addressed in any presentation.

Future marketing opportunities will be limited by the lack of seafood marketinglicence holders in the South-West. This could be overcome if a number of producersestablished and agreed to cooperate in marketing their crayfish, with possibilities of aunique South-West Queensland identity for such a product being marketed through asingle market (and licence) group. The possibility of a good local market was raised

by several people, with a regular flow of tourists, but this market would only takesmall quantities in my opinion.

Artesian water has a temperature of 45-55°C at the bore head, and it was suggested

that this quality could be used to warm ponds in winter. It was explained that flow-through ponds don't provide the optimum conditions in crayfish ponds, butconsiderations could be given to heat exchange methods (e.g. piping in ponds). Thecost may be questionable, but the warm water is available and an experiment may beworthwhile.

It is reported that the local crayfish population is well distributed and in goodnumbers. It should be highlighted to intending producers that the local yabbies andredclaw don't mix and ponds will need to be kept free of this species if successful

production levels are to be achieved. Fencing and netting of ponds also needs to behighlighted, as there was some what of a local sceptical reaction to the suggested

destruction by predators, both land-based and birds.

In the short time on the ground, and Graham's comments a local "industry" of 4-6 producers with upwards of 20 ponds may be possible in the next 2 years. The pondswill be based on both surface and bore water and as well as normal redclaw

production skills. Bore water pond management may require a slightly differentapproach.

Cunnamulla is a long way from the coast and some planning needs to be undertakento service an "established" redclaw industry in the South-West. The Department has areal role and this needs to be addressed. I believe Agribusiness (both QDPI&F andDPI&FE) could and should be involved in the marketing stage of the industry of it


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gets off the ground. A "volume" of redclaw from a unique location could be wellsuited to a niche marketing exercise.

A third stage of any industry development would be the visiting and exposure of

potential producers to established redclaw enterprises. This could take the form of avisit to a region of several redclaw enterprises to allow exposure to different

production methods and farm sizes, the QDPI&F could facilitate such a trip inarranging existing producer contacts. Several interested producers have alreadyvisited one or more enterprises.

Another impression that needs to be addressed is that it is a low-cost industry toestablish, again the typical approach of many about redclaw - dig a hole - throw themin - and harvest at the end of twelve months. The message about costs and systemmanagement needs to be highlighted and reinforced at the proposed seminar.However, a couple of individuals impressed me with the seriousness of their

approach.

The issue of aquaculture permits would need to be covered and some suggestion ofwhere to turn to for assistance and for explanations, again QDPI&F.


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INTRODUCTION TO REDCLAW

Clive Jones

Introduction

Freshwater crayfish are relatively common throughout the world, and several speciesin the northern hemisphere are utilised for food by way of either wild fisheries orfarming. In the southern hemisphere, there is a single family of freshwater crayfish,which in Australia represents over 100 species. Most Australians have somerecollection of catching yabbies in the local creek, however, commercial exploitationof our native crayfish has been quite limited and interest in farming crayfish hasarisen in only the past 10 to 15 years.

The most dramatic introduction to Australia's crayfish is by way of the giantTasmanian crayfish ( Astacopsis gouldi) which can reach in excess of 4 kilograms,although such specimens are likely to be very old. Two other relatively familiarspecies are the Marron from Western Australia and the true Yabbie from severalstates in southern and central Australia. The yabbie, Cherax destructor , is the specieslocal to the Southwest of Queensland. Considerable quantities of yabbies are takenfrom the wild each year, much of which is sold into fish markets in NSW andVictoria. Farming of both these species is undertaken in various parts of southernAustralia, although total production is relatively small, particularly for marron.

Redclaw (Cherax quadricarinatus), is a warmwater species distributed throughout theriver systems of northern Queensland and the Northern Territory flowing to the Gulfof Carpentaria. It also occurs in southern parts of New Guinea.

Within this distribution, redclaw inhabits turbid, slow-moving waters usually in clay-lined billabongs with over-hanging vegetation. Because of the remote distribution,there was very little interest in redclaw until the early 1980's. Recreational fishing waslimited to isolated areas adjacent to towns and of very little significance. Interest froman aquaculture perspective has only arisen in recent years.

Historical Perspective

Farming of freshwater crayfish in Queensland began as a carry-over from marron(Cherax tenuimanus) farming in Western Australia. Despite the involvement of manyfarmers over a considerable period, marron farming had achieved little commercialsuccess. Enterprising farmers from south-east Queensland felt that marron would

perform better in the sub-tropical climate of Queensland. Juvenile marron wereshipped across in 1979, and over several years, a small industry began to emerge

primarily producing juveniles, but in some instances involving several growout ponds. In 1986, the short-lived success was suddenly terminated as higher thanaverage summer temperatures killed off the bulk of marron held.

Just prior to the demise of marron in Queensland, several farmers had begun trialswith redclaw which, being a native of the State, they though would be better suited to


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the south-east Queensland climate. In an effort to protect their capital investment, allthe surviving marron farmers switched to redclaw. In 1987, the QueenslandDepartment of Primary Industries Fisheries Branch proposed a two-year research

program to assess the aquaculture potential of redclaw. This research was conducted

at the Fisheries Research Station at Walkamin, adjacent to natural redclaw populations. The results of this work indicated that redclaw was indeed an idealcandidate for aquaculture.

With the losses incurred by the Queensland marron farmers, and the generalscepticism concerning aquaculture, development of the redclaw farming industry has

been slow. Nevertheless, those involved are optimistic primarily because this species possesses so many advantageous characteristics in regard to its biology, the farmingtechnology required and its marketing. That optimism is now translating intoconsiderable production and substantial industry growth.

Biological Characteristics

The considerable biological advantages of this species are primarily attributable to itsnatural habitat which necessitates broad tolerance of physical extremes. The stillwaters of a billabong in north-western Queensland will often display characteristicswhich many freshwater species would find lethal. Redclaw thrives in thisenvironment.Specific experimentation of growth in relation to temperature indicated tolerance to a

broad range of temperatures. Optimal growth was achieved over the range 23 to 31°C

and lethal levels were estimated to be 10 and 35°C. By way of comparison, the

temperature/growth relationship of the giant freshwater prawn (or Mitchell RiverPrawn), Macrobrachium rosenbergii, indicated a much narrower tolerance totemperature. The range over which redclaw will grow well represents temperatureswhich prevail throughout much of Queensland.

Similar experimentation of salinity tolerance indicated that redclaw will toleratereasonably high salinities (up to 12 parts per thousand) for extended periods. Thistolerance has two advantages. Firstly, farming in brackish water may be feasible, andsecondly the physiological impact of saline treatment brings about a significantimprovement in flavour.

Redclaw also display an extraordinary tolerance of low dissolved oxygenconcentrations. Naturally, as with all aquatic species, production is optimal whendissolved oxygen is close to 100% saturation. However, when dissolved oxygen falls,redclaw remain active and healthy at concentrations as low as 1 ppm (parts permillion). The physiological mechanism involved is similar to that which operates invertebrates, and will sustain the animal for some hours, until oxygen levels areincreased.

Although this characteristic should not preclude good pond management practices, itis comforting to know that if oxygen levels do drop suddenly, redclaw are likely tosurvive. Under similar circumstances, most fish and other crustaceans would suffermass mortalities.


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Although specific assessment of redclaw's tolerance to other physical parameters hasnot been made, it is clear from general experience amongst farmers and researchers,that this species is broadly physiologically robust and will tolerate extremes that manyother species would find lethal.

Feeding Characteristics

The feeding characteristics of redclaw are also advantageous. Under naturalcircumstances redclaw have a broad diet ranging from the simplest organic materialsassociated with decaying plant and animal material, the detritus, through to freshanimal and plant material, when available. The microbial organisms associated withdecaying organic material, primarily fungi and bacteria, are highly nutritious.Consequently, simple organic materials added to a normal earthen pond environmentwhere natural microbial populations are present can provide adequate nutrition. To

provide optimal nutrition, a specific feed formulation is necessary. The development

of such a feed for redclaw is one of the primary research activities at present.

Growth Rate

Growth of crayfish is dependant on a process known as moulting. This involves asequence of stages including; shedding of the external shell; swelling of the body withwater while the new shell hardens; expelling the water; tissue growth until the newshell is full; and so the process continues. Newly hatched crayfish moult every fewdays, but the frequency slowly diminishes to once every few months in large crayfish.

Newly moulted crayfish which are soft are particularly vulnerable to predation by

other crayfish. For this reason, ample shelter, particularly for juveniles, is essential.

Growth of redclaw is dependant on the prevailing physical conditions (primarilytemperature) and the type of nutrition. In addition, there is considerable variability ingrowth rate between individuals. In general terms however, redclaw will achieve asize of between 50 and 100 grams within twelve months. Although a maximum size inexcess of 400 grams is possible, growth rate slows appreciably after the first 12 to 18months and commercial production of crayfish larger than 150 grams is currently notcommercially viable.

Increasing growth rate and the uniformity of growth are also primary objectives of

research. Significant gains are likely to be achieved through nutritional research andselective breeding programs.


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Reproduction

The reproductive characteristics of redclaw are well suited to aquaculture. Both males

and females mature at 6 to 9 months of age and will mate and spawn continuouslywhile suitable temperature conditions prevail. In north Queensland, egg-bearingfemales are found year round although there is a considerable decline in reproductiveactivity from May through July. For the other nine months, females may havesuccessive broods.

After mating, the fertilised eggs are carried beneath the tail of the female whocarefully maintains and nurtures them during the incubation. Incubatory period is alsotemperature dependent, and may range from 6 to 10 weeks. The number of eggscarried is dependant on the size of the female and will vary from around 300 to 1,000

per brood.

Life Cycle

The Redclaw life cycle is very simple. From a farming perspective, the technologyinvolved in accommodating and managing this life cycle can therefore also be simple.Figure 1 below provides a summary of this cycle. After mating the fertilised eggs arecarefully nurtured for about 6 to 10 weeks at which time they hatch to produce a smallcrayfish (about 12mm long) of adult-form, i.e. there is no free-living larval stage.

Figure 1. Diagram of redclaw life cycle.

MATING

HATCHLINGS

JUVENILES

MATURE ADULTS

incubation6 to 10 weeks

adult form0.02g300-1000/fem

rapid growth3 months

5 to 15g50 -100/female

rapid growth6-12 monthssimple food

adults may growto over 400gin 4-5 years

The hatchlings grow rapidly when provided with an adequate diet (preferablyzooplankton) and within 3 months will achieve a size of 5 to 15 grams. They are now

past their most vulnerable stage and will feed on detritus and grow to an average ofapproximately 70 grams (ranging from 50 to 100g) over the next 6 to 12 months.During this period they mature and continue the cycle.


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Disease and Parasites

Several potentially serious disease causing organisms have been identified in redclawincluding a couple of viruses, which could potentially cause major mortalities. This

has been the case with prawn aquaculture, where viruses have caused severe lossesand the demise of large industries. It is clear that the influence of the disease causingorganisms is directly related to crayfish condition. That is, stress-free crayfish, held ingood water quality conditions are unlikely to be affected by disease. Maintenance ofoptimal conditions is therefore crucial.

The only other significant health issues are in regard to organisms fouling the shell.There are a variety of species which will attach themselves to the outer shell or insidethe gill chambers, but most will not cause direct damage. Those occurring mostcommonly include species of flat-worms (Temnocephalans), eggs of water bugs andvarious protozoans. They can be controlled through pond management or if need bewith a saline bath.

Farming Technology

The biological characteristics of redclaw provide technical advantages in regard to itscultivation, particularly when considered in comparison with aquaculture of otherspecies. A significant advantage is conferred simply because the species is physicallyrobust. It can be handled out of water with little adverse affect and without arequirement for specialised handling procedures as are often necessary for fishspecies. This is particularly advantageous for sampling and moving crayfish around

the farm.

Redclaw breed so readily in normal pond conditions, there is no requirement forspecialised hatcheries with environmental control and intensive management. Thelarval phase of the crayfish is entirely contained in the egg, precluding therequirement for sophisticated larval rearing facilities as are required for prawns andother species. The entire breeding, hatching and nursery phases can be managedwithin an earthern pond system. This permits large scale juvenile production with aminimum of capital expenditure and minimum of technical expertise.

A specific and highly advantageous characteristic of redclaw in regard to harvesting is

its response to water current. Like many freshwater species, redclaw respond tomoving water by migrating upstream. This response is particularly strong and has

been harnessed by the development of flow traps. These traps are of various designs, but all work on the principle of attracting crayfish into a trap by way of a watercurrent.

Summary

It is clear that redclaw is an ideal aquaculture species. It will achieve substantial size,is attractive in colour and form, has a good flesh recovery rate and compares well in

flavour and texture with the most sought after crustaceans.


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Its physiological tolerance to extremes of environment is great, particularly in regardto temperature, dissolved oxygen and salinity. Growth is rapid and sufficient toachieve a commercially acceptable size within twelve months. Feeding requirementsare such that a relatively cheap diet will enable significant production in the order of

1.5 to 3 tonnes per hectare. The species is relatively non-aggressive and will performwell at densities of 5 to 10 per square metre. It displays behavioural characteristicswhich lend themselves to efficient harvesting practices.

Redclaw can be induced to spawn with relative ease. Handling of broodstock andincubation of eggs requires no specialised facilities. The larval stage is entirelycontained in the egg which is carefully nurtured by the maternal parent. Thereproductive capacity of the species is relatively high. Juvenile crayfish, althoughfragile, are resilient and respond well to intensive pond production with appropriatefood and shelter.

Throughout all stages of the production cycle, crayfish can be handled easily and witha minimum of specialised procedures and facilities. At this stage, disease and healthare not major issues.

The physical (including climatic) requirements for cultivation of redclaw are broadand reasonably non-restrictive. The geographic potential for the species is thereforesignificant, and extends throughout tropical regions where sufficient water isavailable.


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SITE REQUIREMENTS

Millin Curtis

Site Requirements

The potential of redclaw for aquaculture can only be achieved by providing the rightconditions for good growth and reproduction. Redclaw may survive under poorconditions, but will not grow rapidly enough to sustain the commercial viability of anoperation.

In reaching a decision of where and how to establish a farm, it is important toconsider all the factors, maximising favourable characteristics and minimising anynegative aspects. There is no such thing as the perfect site for freshwater crayfishfarming.

Site suitability is usually judged on the basis of satisfying given criteria.

Site Suitability Criteria

Climate

Temperature is the most important factor in maximising the growth potential ofredclaw. The site should maximise the period each year when pond temperatures

remain between 23 to 31°C. Mortalities may occur if pond temperatures remain below10°C or above 35°C for extended periods. Some sub-tropical regions may presentsuitable conditions for most of the year, but as per Table 1, low winter and highsummer temperatures may cause some problems. Management strategies whichalleviate these extremes may need to be devised. Besides growth, successfulreproduction also requires sustained periods of warm temperatures.

Water Availability

An abundant supply of good quality water, which can be sourced from a surfaceflowing stream, an irrigation channel or from underground is essential foraquaculture. The supply of water must be guaranteed, even during the most severedrought.

The quality of the water is just as important as the quantity. Chemical laboratories cantest samples to determine if the sources of an appropriate quality for aquaculture. Thewater supply must be free from chemicals such as heavy metals, oils, pesticides,herbicides, chlorine, methane, hydrogen sulphide, high iron content, and extremes of

pH. High turbidity, caused by suspended silt or clay colloids, should be avoided as itmay inhibit natural pond production and possibly cause stress through deposition ongills by reducing the ability of the crayfish to respire. Additions of a liming agent and

fertilisers would be routine practice in pond management.


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Caution should be exercised when the utilisation of surface water is proposed as present and previous land management practice involving pesticide application isundesirable. Similarly, upstream discharge of industrial effluents or contamination bydead livestock would be incompatible with crayfish farming.

Bore water, and sometimes artesian water, can be excellent sources for aquaculture.Underground supplies are free of pathogens, predators, pollution and have a relativelyconstant temperature year round.

The quality of underground water must always be checked as it can be deficient inoxygen, or contain excessive levels of carbon dioxide, hydrogen sulphide or iron.Generally, these limitations can be overcome by storing the water in a reservoir andaerating vigorously prior to use.

Table 2. Preferred range of selected water quality parameters of source water,for redclaw aquaculture.

Parameter Acceptable range Comments

Temperature 23 to 31°C Growth will be optimisedwithin this range

Dissolved oxygen > 5.0 mg/l

pH 6.5 to 8.5 Waters should be well buffered.

Total alkalinity > 50 mg/l as CaCO3 < 500 mg/l

Total hardness > 50 mg/l as CaCO3 < 500 mg/l

Ammonia < 0.05 mg/l total NH3 Toxicity increases withrising pH and temperature

Nitrite < 0.05 mg/l

Turbidity NilIron < 0.1 mg/l

Hydrogen sulphide < 0.002 mg/l

Soil Type

In order to hold water, ponds must be constructed from soils containing a high proportion of clay. If clay soil predominates across a site then ponds can beconstructed with a minimum of earthmoving. If clay soil is only present in pockets, itmay not be cost effective to construct ponds because of the expense of earthmoving.


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Soil surveys are advisable to determine if there are sand or gravel layers that couldinterfere with pond construction or limit water retention.

Soil samples should be taken from any potential sites for pesticide residue analysis as

previous agricultural activity may have involved application of persistent pesticideswhich are incompatible with crayfish farming.

Topography

The land should be gently sloping to enable gravity flow of water, minimise pumpingcosts and facilitate simplicity of pond construction. The land should not be susceptibleto flooding.

Miscellaneous

Other aspects of site requirements which should be considered include:

• Proximity to necessary infrastructure such as workforce, technical expertise,electricity, supplies (hardware, mechanical, feed, fertiliser), processing

• Ability to secure the site against predators and poachers• Desirability of the area as a place to live• Future developments which may impact on crayfish farming• Proximity to both domestic and international markets


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POND AND CONSTRUCTION ENGINEERING ISSUES

Clive Jones, Ian Ross and Colin Bendall

Water Supply

As discussed under Site Requirements, the water supply is one of the most importantrequirements for a successful aquaculture project. The source must be guaranteed ofsupplying sufficient volume during the most severe drought conditions. Points toconsider include:

• Is sufficient volume on-hand to provide pond fill (e.g. for a pond surface area of1000m2 volume required is approximately 1.2 Ml).

• The water supply must be sufficiently reliable to provide year roundreplenishment of evaporation and seepage losses. For example, the volume forevaporation losses for a 1000m2 pond is approximately 2.5 Ml for the Cunnamulladistrict.

• Is water of suitable quality? See recommendations elsewhere.• Does pond effluent need to be stored as part of discharge permit?• Can water be recycled to reduce volume of water required?

Construction Materials

Materials on site need to be investigated to determine their suitability for pondconstruction. Clay soils provide the lowest permeability and therefore little or noseepage losses. Sandy clay soils may be suitable for pond construction providing stepsare taken to minimise seepage. Sands, silts and structured clays are all quite

permeable and therefore require the installation of clay or synthetic liners.

Pond Design

The layout of the ponds is generally determined by the topography. Factors to beconsidered include:

• On sloping sites ponds are constructed as hillside storages i.e. banks on threesides.

• On flat sites ponds are constructed as excavated tanks i.e. banks on four sides.• Flat sites are not desirable due to the difficulty in fully draining ponds for

effective harvesting and drying.

• Sloping sites provide better pond drainage opportunities by using gravity.• Slopes of around 2 to 5% (1:5m to 1:2m) provide the best storage to excavation

ratio, i.e.the least amount of earthworks to provide the storage required.

• Surface drainage may be required to exclude runoff from surrounding areas.

• It is important to consider all aspects of the project before commencing pondconstruction so that best use of topography and existing facilities can be achieved.


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Pond Details

• Ponds are usually rectangular in shape.• Surface area can vary from approximately 700 to 2000m2, with the average

around 1000m2, i.e. 50m x 20m at water level.• Batters 2.5:1 outside, 2:5:1 inside, for dozer construction.• Batters 2.5:1 outside, 3.5:1 inside, short end, for scraper construction in clay.• If lining is required, 3:1 inside, 2.5:1 outside.• Min Base dimension - 30m x 6m for scraper construction. Smaller bases can be

achieved with dozer construction.

• Min Crest width of 2.5m for construction equipment safety on crest.• Base of pond should slope to drainage outlet to allow full drainage of pond.• Recommended depth of 1.2m (shallow end) to 1.8m (deep end).• Inlet pipe around 100mm for fast filling and topping up.

• Outlet pipe 200mm diameter (minimum) for effective drain harvest.• Inlet and outlet pipes at opposite ends of pond.• Concrete or loose rock pads are required at inlet and outlet to prevent erosion.• Galvanised steel sheet "Water Rat" wall to be placed around pond - 600mm high.• Predator proof netting supported above ponds by timber posts and steel cable.

Lining Materials

Clay Soils

• Strip topsoil and stock pile for placement on constructed embankment.• Construct embankment using suitable clay material with correct moisture content.• Compacted central clay core and cutoff will prevent loss of water through

seepage.

• Use thin layers (200mm Max) to be compacted by sheeps foot roller.• Outlet pipe to be installed using baffles around pipe to prevent seepage.

Clay Lining

• Is suitable clay material available on site or is cartage from elsewhere required.• If cartage is required - placement and compaction with moisture control may

result in greater cost than synthetic liner e.g. Clay Liner - Walkamin area $7.50/m3 or $2500 for 1000m2 pond.

• Batters 3:1 to 3.5:1 inside to allow spreading and compaction of lining material.• 300mm minimum liner thickness.• Minor seepage will still occur with clay lining.

Synthetic lining

• Many types and thicknesses available.• Materials - Polythene/P.V.C/HDPE.•

Mechanical strength (resistance to puncture and tearing) increases with type andthickness of material.• Materials come in rolls 1.4 to 8m in width


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• Joining of strips is by hot welding or adhesive tapes.• Priced from $1.10 to $4.00 per square metre depending on material.• Surface to be lined should be free from rocks and sticks.• Sand bedding may be required if soil surface too rough or stony or higher grade of

lining material should be used.• Liner is anchored in excavated trench, approximately 300mm deep at edge of

crest.

• HDPE type materials require deeper trench to be located up to 0.5m from edge ofcrest to resist expansion / contraction forces.

• 300mm minimum lining of top soil over liner required to protect liner from U.V.and to provide a natural environment for crayfish.

• Subsurface drainage may be required to prevent soil water pressure from liftingliner.

Basic steps in Pond Construction

• Clear the site area of vegetation, including stumps and roots.• Strip the pond and surrounding bank area of topsoil and stockpile it for later use.• Excavate the core trench in the middle of the proposed surrounding embankments

at least 3 metres wide and at least 0.3 metres deep into impermeable clay beneaththe bank.

• Excavate and install the outlet pipes under the proposed embankments ensuring tocarefully compact the backfill clay around the pipes and baffles.

• Refill the core trench with layers of compacted clay originating from the excavated pond, ensuring each successive layer is no more than 0.2 metres thick.

• Preferably site construction plant should include a scraper, sheepsfoot roller andwater truck..

• Continue construction of the clay core and outer embankment zones until thedesign crest height is reached.

• Excavate ponds to designed depth and shape, then compact base and sides of pondwith sheepsfoot roller.

• Spread a minimum topsoil cover of 100 millimetres over total pond andsurrounding embankment area.

• Quickly establish a dense ground cover of suitable holding grass i.e. kikuyu,couch, pangola, African star etc. on crest and exposed batters of the ponds to

stabilise the soils and reduce erosion.


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PRODUCTION TECHNIQUES FOR REDCLAW

Clive Jones

Introduction

There is a common misconception that farming of redclaw involves nothing muchmore than throwing a few crayfish into a dam. Redclaw aquaculture is an intensivefarming activity requiring daily management of a range of processes. Consequently,to achieve efficiency and maximise productivity, and therefore maximise success and

profit, the various processes should be streamlined and linked together. A systematicapproach must be taken. Naturally every farm is unique and every farmer has thereown way of doing things. The following concepts are therefore of a general natureand would need to be modified and adapted to suit each individual farm.

It should be noted that there are many redclaw enthusiasts who have taken a quitedifferent approach to that outlined here. Their approach generally takes the form ofmanaging semi-natural populations of redclaw in ponds which are never (orinfrequently) drained. Crayfish are continually harvested by traps and naturalreproduction in the pond takes care of re-stocking. While this approach will producecrayfish, it is not considered commercially viable as a dedicated farming activity.

For this discussion, I have also deliberately omitted any considerations of post-harvest, marketing and business issues, not because they're not important, on the

contrary, they're so important and so numerous, that they justify separateconsideration.

The farming of redclaw can effectively be considered an amalgamation of thefollowing processes.

• Supply of juveniles (farm production, purchased)

• Stock management (broodstock, culling, health/disease, predators)

• Harvesting (partial, total)

• Feeding (what, when, how much, how often)

• Pond management (pond preparation, water quality, environment)• Post-Harvest• Marketing • Application of good business principles (book-keeping, costs, income)

To illustrate the development and operation of a redclaw farm I will use ahypothetical model farm. Naturally for the purposes of this introduction these notesare quite general. More comprehensive and detailed considerations will be necessary

before embarking on a commercial operation.

I have assumed that a suitable site has been selected as discussed previously. The

model farm includes 40 by 1,000m

2

growout ponds (i.e. a production capacity of 4hectares), 15 by 1,000m2 juvenile production ponds and other facilities as marked inthe diagram.


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Figure 2. Layout of a hypothetical redclaw farm consisting of forty 1,000m2 production ponds.

SETTLINGDAM

SUPPLYDAMGROWOUT

PONDS

JUVENILE PRODUCTION PONDS

The ponds, as discussed previously under 'Pond Construction', should be 1 to 2 metresdeep, with good slope from shallow to deep end, and a large bore drainage pipe at thedeepest point, running through the pond wall. Quick (approximately 24 hours) andcomplete drainage is essential.

Farm Layout Considerations

• positioning of ponds (optimising use of slope, minimising materials e.g. pipes,fencing, netting, allowing flexibility for expansion)

• position of central facilities (minimise travel distances); tanks (for holdingharvested crayfish), feed storage, general storage, electricity supply, blower,sorting/packing area, office, etc.)

• supply and settling ponds

• drainage (gravity drainage of all ponds is recommended)

• netting (essential to prevent bird predation)

• fencing (essential to prevent rat predation, and to prevent migration of crayfish)

• aeration (essential to maintain dissolved oxygen levels and to provide pondcirculation)

Juvenile Supply


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There are two options for obtaining a supply of juvenile crayfish; purchase them fromanother grower, or produce them on the farm. Given the ease with which redclaw will

breed and rear offspring, production on the farm is the usual choice. This may changein time when specialist juvenile production farms ('hatcheries') with superior genetic

stock are established.

Although a typical female of average size may lay and incubate between 300 and1,000 eggs, there is considerable attrition before these offspring achieve a size of

between 2 and 20g when they are referred to as advanced juveniles, and are ready forstocking to growout ponds. As a rule of thumb, each female is considered capable of

producing 50 advanced juveniles per brood.

Juvenile production ponds are usually of the same specification as growout ponds,although they are managed a little differently, particularly in regard to provision ofsuitable shelter and planktonic food. Our model farm ponds of 1,000m2 would

normally be stocked with around 100 mature females and between 25 and 100 males(carefully selected as the best of the stock available). On the basis of 50 advanced

juveniles per female this pond would therefore produce 5,000 juveniles for stocking tothe growout ponds. This number is suitable for a complete stocking of one growout

pond at 5 crayfish per square metre, a standard stocking density.

Under North Queensland conditions, a juvenile production pond, stocked as specified,would be ready for harvest in 4 months. Thus, the 15 juvenile production ponds,

producing 3 times per year can supply 45 batches (5,000 in each) of advanced juveniles per year. This is sufficient, with some excess, for the 40 growout ponds.

This strategy will necessitate a juvenile pond harvest about once every week.

To maximise survival and growth of the juvenile redclaw, an abundance of shelter inthe ponds is essential. This is usually provided in the form of bundles of syntheticmesh, tied onto a line with a weight at one end and a float at the other. Arranged inthis manner, these bundles extend from the pond floor up into the water column

providing many spaces and surfaces for the juveniles to utilise. In the 1,000m2 model ponds, at least 200 mesh bundles are required.

Juvenile production ponds are carefully managed to provide an abundance of planktonic organisms which the juvenile crayfish utilise as food. These planktonic

organisms are the microscopic creatures which live in the water, and include both plants (phytoplankton) and animals (zooplankton). It is primarily the zooplanktonwhich are consumed by the juvenile crayfish. As they grow, they progressivelyconsume less plankton and more detrital food which occurs on the surface of theshelter material and more particularly on the mud surface.

Maintaining high levels of plankton involves regular checking of water quality and periodic fertilisation of the water.

Harvesting of the juveniles (about 4 months after stocking) can be achieved by anumber of methods. Individual mesh shelters can be removed and the juveniles

shaken out. However, the most effective method is to employ the flow trap, the designand operation of which is explained elsewhere. With this method, the pond is


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completely drained and all the crayfish are attracted into a trap. From here they can beremoved to the central tank facility and sorted, counted and then stocked to thegrowout ponds. Generally speaking, there will be some excess juveniles. The best (i.e.the largest and healthiest) should be selected for stocking, and the remainder removed

from the farm (sold to other farms or to the bait market) or destroyed. The juveniles to be stocked to the growout pond should be transferred to the growout pond late in theafternoon or early in the evening.

Stock Management

Stock management primarily concerns the growout stage. As mentioned above,growout ponds are normally stocked with advanced juveniles at around 5/m2. For ourmodel ponds, this means 5,000 juveniles.

Shelter is again important. For the growout stage some mesh shelters may be used as

well as some of different specification. For our model farm we will use mesh sheltersand 'highrise' shelters made from agricultural drainage pipe. Each highrise shelterconsists of 150mm lengths of 50mm pipe clipped together in a stack 10 wide by 3high. This will provide adequate shelter for at least 30 crayfish. One hundred meshshelters and 100 highrise will be used in each growout pond.

The growout phase would normally be in the order of 12 months. Some farmersharvest more frequently to enable culling of runts and staging of crayfish into uniformsize groups for further growout. This can be beneficial, but is dependant to someextent on total number of ponds and available labour. For the purposes of our model

farm we will work on the basis of 12 months growout per pond. Consequently, therewill be 40 growout pond harvests per year, or one approximately every 9 days.

In order to gauge crayfish size (for determining feeding rates) and health/condition (toensure pond management is optimal), regular sampling of each growout pond isrecommended. For this model farm we will stipulate 3 samples per year for eachgrowout pond, meaning a sample every 3 days. The sample can be taken by retrievinga few of the shelters, or by baited traps. The captured crayfish should be weighed, andthe results used to adjust the feeding schedule. The condition of the crayfish can beobserved with particular attention paid to tail blistering, growths on the shell andgeneral vitality of the animals. Any problems should be addressed by a review of

water quality and appropriate adjustments.

The 12 month growout period is sufficient for the entire crop to achieve market size(i.e. >50g). At harvest, the crayfish will initially be sorted into 3 groupings. Thefastest growers, i.e. the largest will be selected out as breeding stock. As indicatedabove, about 100 females and up to 100 males will be required per juvenile

production pond. So, the best 100 females and males from the growout harvest will beused for breeding. All crayfish down to 50g will be separated for market. These mayrequire further size and quality grading prior to leaving the farm. All crayfish under50g are considered runts and unwanted juveniles. If they can be sold to other farms orother markets, well and good. Otherwise they must be destroyed.


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Another important facet of stock management is prevention or minimisation of predators. This will primarily be achieved by the netting and fencing installed duringfarm construction. However, on-going observation for indications of predator activityis important. Both water rats and birds will leave tell-tale signs of their presence. Such

signs should prompt closer inspection of nets and fences for holes and gaps etc.. Asmall number of predators can achieve significant damage over time. Eels are also amajor concern, but only in coastal areas.

Harvesting

As indicated above, the harvesting timetable involves 45 juvenile production ponds per year and 40 growout ponds per year. On the basis of continuous year-round production, there will be a harvest of both a juvenile and growout pond every week to9 days.

For both juveniles and growout, the flow trap harvesting technique will be employed.The design and operation of the flow trap is well explained in a video available fromthe DPI&F&F (contact Clive Jones). It involves a trap which harnesses the redclawsstrong response to flowing water. It is very efficient and ensures crayfish remain inoptimal condition. The trapping occurs while the pond is being completely drained,usually overnight.

Harvested crayfish (both juvenile and grown out) are taken from the trap in the pondimmediately to a tank holding facility. The post-harvest procedures of sorting,grading, re-stocking, or packaging for transport are completed here. Crayfish from the

juvenile production ponds should be sorted quickly and released into a growout pond, preferably on the same day. This will necessitate previous preparation of a growout pond (see below).

Feeding

As indicated in the previous discussion of crayfish feeding habit, the food consumed by post-juvenile and adult crayfish is primarily the decaying organic material on the pond mud surface, referred to as the detritus. To maximise the availability andnutritional quality of this food source, organic materials are added to the pond on aregular basis. This is usually in the form of a pellet.

Nutritional research is proceeding towards developing optimal diets in pellet form. At present, adequate diets are available from several feed manufacturers throughout theState. Chicken pellets should be avoided. A specific crayfish pellet with a proteincontent of around 20% is recommended.

The amount of feed provided to the pond is based on the biomass, that is, the totalweight of stock in the pond calculated from the number of crayfish and their averagesize. At first stocking of growout ponds feed is provided at about 12% of biomass 3times per week (equivalent to 5% per day). This equates to about 6kg of food for eachfeed in the 1,000m2 ponds. As the crayfish grow a smaller percentage of the biomassis fed, down to about 5% of biomass 3 times per week (equivalent to 2% per day).Close to harvest, this would mean about 10kg of food at each feed. The schedule


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prepared is a rough rule of thumb. Adjustments up or down must be made on the basisof regular observation of ponds for uneaten food, and according to the size of thecrayfish as measured from regular sampling.

For our model farm feed will be purchased in bulk and stored in a small silo.Approximately 48 tonnes of feed per year would be required. Fresh feed can be

purchased every month, requiring a silo capacity of 4 tonnes. Distribution of feed toeach pond (3 times per week) will be achieved with a small blower mounted on a 4-wheel bike. Smaller farms would distribute the feed by hand from a bucket.

Feeding of juvenile production ponds is substantially different to growout ponds.Planktonic food is required, and a more intensive management of the pond water istherefore required. Appropriate pond preparation (discussed below) is critical,followed by frequent assessment of plankton density (secchi disk readings) and

plankton type. The bloom of plankton is maintained through regular applications of

fertilisers, both organic and inorganic. Some application of pellet food to the pond isalso necessary to provide detrital food for the juvenile crayfish as they grow andchange their diet. As a rule of thumb about 2kg 3 times per week would be sufficient.

Pond Management

Management of the pond is primarily an issue of water quality management. Someunderstanding of the chemical and biological dynamics of pond water is required. The

parameters which are generally measured and managed include pH, dissolved oxygen, plankton density, water temperature, alkalinity, hardness, ammonia and nitrite. Table

3 below gives some further details of these parameters and their measurement.

Adjustment of the these parameters when they move outside the optimal range mayinvolve additions of various materials such as fertiliser or lime, or flushing of the

pond with new water. Dissolved oxygen levels are maintained by aeration. This can be achieved using a variety of mechanical devices. Our preferred method for themodel farm is using airlift aerators. Briefly, this involves running low pressure airfrom a mechanical blower to the ponds, injecting the air into the base of PVC pipeswhich are held onto the pond floor with a weight. The air rises to the surface, therebyholding the pipe up at the surface, and water is displaced out of the top. The action ofthe airlift provides oxygenation of the water and circulation.


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Table 3. Water quality parameters, their preferred range and measurement forredclaw aquaculture.

Parameter Description OptimalRange MeasuringDevice Frequency ofMeasurement

pH acid/alkaline balance

7.0 to 8.5 pH meter, ortest kit

1 to 3 x/week(am)

DissolvedOxygen

Oxygendissolved inthe water

> 4.0ppm, or> 80% satur.

Dissolvedoxygen meter

1 to 3 x/week(am)

Planktondensity

Abundance of plankton

30 to 70cm Secchi disk 1 to 3 x/week

Temperature Maximum &minimum

Max. 31CMin. 20C

Max/minthermometer

1 x/week

Alkalinity Bufferingcapacity ofwater

>40ppm Test kit, or labanalysis

1 x/year

Hardness Concentrationof Ca and Mg

>40ppm Test kit, or labanalysis

1 x/year

Ammonia Toxic waste product


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It should be clear from these notes that redclaw farming is an intensive farmingactivity which requires daily attention, a broad range of skills and knowledge and acommitment to a range of principles. If this approach is adopted, the potential returnscan be very attractive (see Economics section).

Because of the skills and knowledge required, those interested in starting a redclawfarming operation should obtain as much information as possible. Crayfish farmingAssociations operating throughout the State will provide access to existing farmerswhose experience will assist those new to this enterprise.


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FARM MANAGEMENT

Clive Jones

I have defined 7 steps to a systematic approach to redclaw farm management.

1. Your Objective

Firstly, if you're serious about a systems approach to farming, you need to have setsome overall Objective, a Mission Statement which sums up what you plan toachieve.

This objective might be something like:

To create and operate a redclaw farm where facilities and operations are organised

to optimise efficiency and to maximise output of premium product and financial

return.

2. Recognising the Processes

Next, you need to recognise the various processes which collectively make-upredclaw farming.

• Supply of juveniles (farm production, purchased)

• Stock management (broodstock, culling, health/disease, predators)• Harvesting (partial, total)

• Feeding (what, when, how much, how often)

• Pond management (pond preparation, water quality, environment)• Post-Harvest• Marketing • Application of good business principles (book-keeping, costs, cash flow, repairs &

maintenance)

3. Developing the Strategy

The third step is to develop a strategy of how you plan to carry out these processes.For example your strategy for supplying juveniles to your farm may be to produce100,000 x10g male only crayfish in your own dedicated juvenile production pondseach year on a continuous basis. Strategies for all the processes should be defined.

i) Farm Layout (see Figure 2)

• positioning of ponds (optimising use of slope, minimising materials e.g. pipes,fencing, netting, allowing flexibility for expansion)

• position of central facilities (minimise travel distances); tanks, feed storage,

general storage, electricity supply, blower, sorting/packing area, office, etc.)• supply and settling ponds• drainage


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• netting

• fencing

• aeration

ii) Juvenile Production

• produced on farm

• farm requires 200,000 advanced (5-20g) juveniles per year (based on stockingdensities given below)

• farm requires 4,000 breeding females (+ appropriate number of males) to generate juveniles (based on production of 50 advanced juveniles per female)

• breeding ponds to be stocked at 100 females (25 to 100 males)(to generate 5,000advanced juveniles)

• juveniles to be sold only if excess available

iii) Stock Management

• breeding and growout will be managed as separate processes

• broodstock will be actively selected from each growout harvest (i.e. best 100female and male)

• everything under 15g at growout harvest will be destroyed/discarded• crayfish 15 to 50g sold to juvenile market (e.g. other farmers or overseas)

• all crayfish 50g + to be sold to market, all year round

• health and disease status will be monitored

• predation proofing will be applied

iv) Harvesting

• growout ponds to be harvested by total drainage and flow-trapping (once everyyear)

• breeding ponds to be harvested by total drainage and flow-trapping (every 3months)

• pond water directed to settling pond, re-used

v) Feeding

• good quality pellets to be used (15-20% protein)• feed to be stored in bulk silo (4 tonne capacity)

• feed purchased in bulk

• requirement for 48 tonnes of feed per year (based on feed conversion ratio of 4,and production rate of 3 tonnes per hectare)

vi) Pond Management

• pond preparation to include liming (100kg/pond), DAP (20kg/pond), lucerne chaff(150kg/pond)

• water quality will be measured in all ponds including pH, dissolved oxygen and

secchi (3x/wk), hardness and alkalinity (once/yr), ammonia and nitrite (asnecessary)


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• water quality of source water will be measured annually by full analysis, including pesticides and heavy metals

• the pond environment will be maintained by keeping pond depth at full, regularadditions of fertiliser, or flushing as determined by water quality

• ponds will be dried for at least 2 weeks between crops

4. Allocating Resources

Your strategies should be realistic in regard to the resources you have on hand, e.g. ponds, water supply, capacity to handle crayfish etc. Your resources must be allocatedin a way which makes optimal use of them. For example, it is not much use producing200,000 juveniles if you have no facility to handle them or there are no ponds ready to

be stocked.

• Ponds. Each breeding pond to be managed to produce juveniles for one growout

pond. Harvesting breeding ponds every 4 months (3x/yr). 15 breeding ponds willservice 40 growout ponds, with some excess. It is important to note here that eventhough there are 55 ponds, only 40 (4ha) are for growout production, and

production rates are based on these.

• Water. 5.5 hectares of water (including all ponds) at 1.5m average depth = 82,500cubic metres = 82.5 Megalitres. Anticipate evaporative loss of 2.5 metres per year(for South-West Qld.) = 137.5ML. Harvesting each growout pond once per year =60ML. Harvesting each breeding pond 3 times per year = 67.5ML. Plus seepageand other uses = 10ML. Water required 297.5ML for the first year, and 215ML/yrfor successive years. Factor water required into supply dam size, pump capacity

etc. Clearly, savings can be made by re-using water at harvest.• Air Blower, sufficient to run 6x100mm airlifts per pond, i.e. approximately

33,000l/min capacity

• Habitats. Highrise and mesh bundles. Minimum of 100 of each per pond.

• Flowtrap. One is sufficient. Possibly a second with different specifications for juvenile harvesting.

• Scoopnets

• Crates, enough to handle at least one total harvest (300kg), at 10kg per crate = 30crates.

• Tanks, enough to hold at least one total harvest (300kg), at 10kg/m2 = 30m2. 6tanks 2.5m diameter.

• Feed, silo with 4 tonne capacity• Buckets, sufficient for feed distribution

• Scales, for weighing harvested crayfish and feed quantities, maximum capacity50kg

• Balance, for weighing individual crayfish

• Water quality equipment, pH meter, dissolved oxygen meter, secchi disk, reagenttest kits for hardness, alkalinity, ammonia, nitrite.

• Store-room, for fertiliser, hay/chaff, lime, boxes, general equipment

5. Setting Timetables

Because there is a certain amount of predictability to growth rates of crayfish, or preparation time for new ponds etc., it is both possible and extremely desirable to map


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out activities in relation to time. For example, if the strategy is to provide 50 to 90gcrayfish to the market all year round, then a harvesting timetable which permits this isessential.

• Juvenile Production, all year round• Stock Management, sampling growout ponds 3x per year each, to check

health/condition and to gauge size (relate back to feeding rate)

• Harvesting, each of 15 breeding ponds to be harvested 3 time per year, i.e.approximately 1 every week; each of 40 growout ponds to be harvested once peryear, i.e. approximately every 9 days

• Feeding, feed purchased in bulk every month to maintain freshness/quality. Feed provided every day at dusk. Feed silo cleaned out once per year to prevent fungalcontamination

• Pond Management, water quality measured twice per week (pH, DO, secchi).Aeration provided midnight to 8am

6. Identifying Assessment Criteria and Standards

To ensure that all activities and processes are operating optimally, you need standardsagainst which to measure your performance. It should be possible to set some criteriaor value for most processes on the farm. An obvious example is water quality. Youshould already be aware that dissolved oxygen should always be above 4 parts permillion, or that pH should be between 7.0 and 8.5. Similarly, standards should be seton all processes.

•

Juvenile Production, minimum of 5,000 5 to 15g juveniles to be produced fromeach breeding pond

• Stock Management, Broodstock selected - lively, >120g (at 12 months age),colour etc.; Growout stock health/condition - external growths, tail blistering,disease symptoms; Growout production of 150 to 300 kg per pond

• Harvesting, percentage of crayfish caught by flowtrap Vs percentage left behind(95:5), number of mortalities, time taken to retrieve harvested crayfish

• Feeding, quality of feed - fungal growth, odour, clumping, dust. Quantity of feed per pond based on prepared schedule, adjusted relative to sampling results

• Pond Management, water quality levels (pH 7.0-8.5, DO >4.0, secchi 50-70cm,hardness/alkalinity 20-100ppm, ammonia/nitrite


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some action should be taken. For example, pH is greater than 9.0, flush the pond.Hardness is less than 20ppm, add lime. The flowtrap catches only 80% of the crop,review the procedure.

Conclusion

This listing is reasonably comprehensive, but is by no means the whole story.However, it should give you a start in developing your own systematic approach toredclaw farming.

Some of you may have recognised that this Systems Approach is similar to theconcept of Total Quality Management (TQM), and that the setting of criteria andstandards to measure performance is effectively Quality Assurance (QA). It's true, justdifferent terminology.

The practices of TQM and QA are most commonly applied to the post-harvest andmarket sectors. Whatever they may be called, the value of these philosophies for the

production chain is also clear. Many farmers may suggest that this Systems Approachis too involved and impractical. It has to be something you as a farmer are committedto and feel comfortable with. I accept that many of the aspects I have covered might

be observed rather than measured, and might be remembered rather than writtendown. Nevertheless, the likelihood of achieving your objective, your mission, will bevastly improved if a methodical, clearly defined systematic approach is applied.


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WATER QUALITY

Millin Curtis

A basic understanding of some of the properties and dynamics of the pond water isessential for maximising crop yield. Measurement of water quality does not replaceobservation of the crayfish stock, but provides additional data to foster informeddecision making. The quality of water in ponds has a direct effect on crayfish healthand performance. If water quality deteriorates, crayfish become predisposed toretarded growth, disease and migration. Proper management of the water commenceswith pond preparation and continues throughout the life of the pond. Good pondmanagers will be able to predict when water quality deterioration may occur and takeremedial action. Reacting to poor water conditions as they occur or after the fact isnot good practice.

Pond Preparation

Liming

Liming deals with problems associated with the acid - base relationship in soils orwater. Liming is not fertilising but may increase the response of fertilisation bymobilising nutrients.

Table 4. Liming and non-liming compounds used for aquaculture ponds.

Formula Compound Common Names Neutralising Value(%)

CaCO3 Calcium Carbonate Agriculturallimestone

100

Ca(OH)2 Calcium Hydroxide Hydrated limeBuilders limeSlaked limeCaustic lime

136

CaO Calcium Oxide Quick limeUnslaked limeBurnt lime

179

CaMg(CO3)2 Calcium Carbonate /Magnesium Carbonate

blend

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