Redclaw (Cherax quadricarinatus) 1

2  Endemic to Australia  3 Cherax species : Excellent candidates for commercial aquaculture Redclaw (C. quadricarinatus) Yabby (C. destructor) Marron (C. tenuimanus) Figure 1. Natural distribution of redclaw, yabby and marron (Wingfield, 2008)

Redclaw YabbyMarron 3

4  Freshwater crayfish are an ideal aquacultural commodity ● H ave excellent flavour and lobster-like appearance - high market value ● No larval stages - no need for expensive sophisticated hatcheries ● Omnivorous, opportunistic feeders - can be fed with inexpensive feeds ● More sustainable than prawn culture - no need for higher stocking densities / expensive coastal sites  Female redclaws bearing eggs and juveniles

 The largest operating cost (> 50%) of most fish and crustacean farming  Fish meal (FM) and fish oil  Expensive  Future availability ? (climate change / overexploitation)  Research priority  Reduction of dependency on FM and fish oil inputs  Identification of alternative high-protein and low-cost feed ingredients  Feed optimization  Require specific nutrient requirement identification  Understanding of digestive enzyme activities of target species 5

6  ECE discovered in commercially cultured decapod crustaceans including freshwater crayfish  ECE enables freshwater crayfish to breakdown complex polysaccharides (e.g. cellulose) and utilise plant-derived ingredients Cellobiose / cello-oligomers Glucose Cellulose

7  Previous growth and digestibility studies  Protein and lipid digestibility widely assessed  Less information on carbohydrates (types/amounts)  Effect / potential of soluble cellulose not investigated  C. destructor & C. tenuimanus less evaluated

8  Objectives To investigate the effect of soluble dietary cellulose on growth performance and digestive enzyme activities in 3 Cherax species  Growth performance: Feeding trial  Enzyme activities: Enzyme assay

(I) Feeding trial Diets: Reference diet (RD) Test diet (TD) n= 34 Feeding: 3% per day, twice 9 Table 1. Composition of experimental diets

(I)Feeding trial  Culture: 12 wk independent trials Table 2. Culture conditions maintained through out the experimental period  Outcome:  Analysis : Two-way ANOVA 10

11  Aquaculture facility – QUT Pilot Plant Precinct, Banyo, QLD  Individual tank unit with cages  Specifications:  36 tanks / 27 L each  Recirculating /purifying system  Automatic control of pH, temp., CD at a set value  Constant water exchange rate at a desired value

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13 (II) Enzyme assay  Enzymes assayed from the Hepatopancreas  Protease  Amylase  Cellulase  Specific enzyme activity (enzyme units (U) per milligram of protein) was calculated  Methods  As described by Pavasovic et al. (2004)  Analysis: Independent “t” test

14 (I)Feeding trial  Redclaw: SGR of (RD) significantly higher than (TD)  Lower survival rates observed in TD than in RD  Overall, females showed higher survival rates [Significance level = p<0.05] SpeciesDietSGR Survival rate (%) FemaleMaleTotal Redclaw RD0.193±0.019 a a 88.2 a 94.1 a TD0.093±0.019 b 94.1 a 64.7 a 79.4 a Marron RD0.146±0.019 a a 94.1 a 97.1 a TD0.107±0.017 a 88.2 a 94.1 a 91.2 a Yabby RD0.105±0.018 a 82.4 a a 91.2 a TD0.086±0.017 a a 64.7 b 82.4 a Table 3. SGR and Survival rate (%)

15 Table 3. Specific enzyme activity levels (±SEM) in the hepatopancreas. (II) Enzyme assay [Significance level = p<0.05] SpeciesDiet Average specific enzyme activity (U/mg of protein) ProteaseAmylaseCellulase AZO-Casein AZCL-HE- Cellulose AZO-CM- Cellulose (X ) Redclaw RD2.469±0.18 a 3.731±0.31 a 3.408±0.20 a 9.690±0.62 a TD1.718±0.23 b 2.257±0.30 b 2.985±0.33 a 7.338±1.12 a Marron RD0.622±0.07 a 0.168±0.02 a 2.492±0.24 a 5.535±0.54 a TD0.315±0.04 b 0.079±0.01 b 1.540±0.16 b 2.203±0.27 b Yabby RD1.409±0.11 a 2.753±0.21 a 1.151±0.08 a 4.372±0.38 a TD0.930±0.13 b 2.025±0.24 b 0.861±0.09 b 2.435±0.29 b

16  All three species responded in same direction for experimental diets  They appear to utilize starch more efficiently than soluble dietary cellulose  Inclusion of 20% soluble cellulose did not appear to have a significant negative effect on individual growth rate in yabby and marron  However, digestibility of soluble cellulose is needed to investigate  Further testing (lower levels) needed to evaluate potential of soluble cellulose to be used as a feed ingredient in commercial formulated diets  Results provide useful information towards formulating low cost crayfish diets for commercial aquaculture

17  Supervisory team  Ridley Agri products, Australia  Crayfish suppliers  Cherax Park, QLD  Aquatic Resource Management Pty Ltd, WA  Burns Yabby Farm / Reedy Creek Crays, NSW  Technical staff at QUT  Family & Friends

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