Aquaculture Nutrition 1998 4; 143–149

Growth and condition of marron Cherax tenuimanus fed pelleted diets of different stability J. JUSSILA Department of Applied Zoology, The University of Kuopio, Suomi-Finland L. H. EVANS Aquatic Science Research Unit, Muresk Institute of Agriculture, Curtin University of Technology, R&D Centre, Technology Park, Bentley, Western Australia

Abstract Six groups of 0 1 marron Cherax tenuimanus were reared on commercial marron diets based on two different fish meals in a study lasting 4 months. Both diets were prepared in a stable and an unstable pelleted form. Marron fed with koi carp or salmon diet and unfed were used as reference groups. Marron were –2 reared communally in tanks (5 m ) and individually in an inten–2 sive crayfish culture system (ICCS, 25 m ). Marron were fed at the rate of 6.5% of their body weight per week. Groups fed with stable diets showed larger weight increment at moult, shorter intermoult period, and higher specific growth rate than groups fed with similar unstable diets. Stable marron diets resulted in faster growth than fish diets. There were no differences in hepatopancreatic indices of marron fed with stable diets or similar unstable diets in the ICCS. The condition of hepatopancreata of marron reared in communal tanks were better than those of marron reared in the ICCS on a similar diet. Results indicate that marron production can be improved using stable pelleted diets in both intensive and semi-intensive culture. KEY WORDS:

Cherax tenuimanus, condition, growth, marron, pellet water stability

Received 18 November 1996, accepted 20 November 1997 Correspondence: Japo Jussila, Aquatic Science Research Unit, Curtin University of Technology, Unit 7, R&D Centre, Technology Park, 1 Sarich Way, Bentley 6102, Western Australia (e-mail: [email protected])

Introduction Crustacean feeding patterns are characterized by slow intake, prolonged handling and long intervals between food intake (Farmanfarmaian et al. 1982). These behavioural characteristics place high demands on the physical form and texture of artificial feeds used in crustacean culture, in particular water stability. Stable pellets are widely used in fish and crustacean culture and the addition of different binders or the use of extrusion manufac-

turing methods are the major strategies used to enhance water stability of pellets (Heinen 1981; Lee & Wickins 1992; Cuzon et al. 1994). Lim & Cuzon (1994) concluded that while pellet stability is of major importance in shrimp nutrition, the loss of nutrients could not be evaluated solely on the basis of pellet water stability. Conversely, Bordner et al. (1986), in studies with juvenile lobsters, concluded that pellet integrity and leaching were not important factors in the growth and survival responses to a particular diet. Productivity in semi-intensive and in intensive culture, is dependent on commercial diets, with up to 50% of nutrients derived from pellets in semi-intensive conditions (Apud et al. 1983). Formulated feeds are even more important in highdensity farming to ensure commercially viable production levels (D’Abramo & Robinson 1989). In addition, McClain (1995a) observed a significant improvement in crayfish condition, expressed as hepatosomatic ratio, as a result of better nutrition. Commercially manufactured diets for crayfish culture, commonly used in Western Australia, have low water stability and disintegrate within minutes after immersion in the water. During our previous experiments with an intensive system (J. Jussila, unpublished observations) marron Cherax tenuimanus appeared to ignore pellets after they had disintegrated in the water. Salmon and koi carp pellets are occasionally used as supplemental diets by commercial marron farmers; these pellets tend to stay intact after addition to culture ponds but pellet integrity and leaching in these and other diets used in marron aquaculture have not been studied. The objective of this study was to test the effect of pellet stability on marron growth and condition in intensive and semiintensive culture. Comparisons of growth performance were made on treatment groups fed diets of different formulations and pellet stabilities. The trials were performed in two different culture systems, in an intensive crayfish culture system (ICCS) where crayfish are reared in high densities and in culture tanks where animals were reared in densities similar to those in semiintensive commercial farm ponds.

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J. Jussila & L. H. Evans Table 1 Proximate analyses of the experimental diets based on the information provided by the pellet manufacturers 1

–1

Crude protein (g kg ) –1 Crude fat (g kg ) –1 Crude fibre (g kg ) –1 Ash (g kg ) 1 2

1

Marron diet D1

Marron diet D2

Salmon diet (D3)

Koi carp diet (D4)

300 90 30 2 120

310 90 30 2 110

480 220 10 2 90

330 40 50 120

Stable and unstable formulation. Analysed by authors.

Materials and methods Four different feed formulations were studied (Table 1): fish meal (Fish meal 65, Vereinigte Fishmehlwerke, Cuxhaven, Germany) based marron diet (D1; stable and unstable; Table 2); dried fish (West Australian pilchards (Mulie) Sardinops neopilchardus, obtained fresh, minced and dried prior to incorporation into feed mixture) based marron diet (D2; stable and unstable; Table 2); salmon diet (Vextra Mini 2, Suomen Rehu OY, Finland; D3) and koi carp diet (All Pet Fish Pellets, Allpet Products, Perth, Western Australia; D4). The two stable marron diets (D1 and D2) were prepared by using a proprietary technique and the unstable formulations of D1 and D2 were then produced by remincing and repelleting the stable pellets using the usual manufacturing methods. The dry weight loss of diets D1–D4 was tested by immersing pellets (stable pellets n = 10; unstable pellets, three replicates) in water at 22°C for 10, 20 min and 1, 2, 3, 6 and 20 h and comparing dry weight before and after immersion. After immersion, most of the water was removed from beakers using Pasteur pipettes without disturbing the pellets and remainder was evapo–1

Table 2 Marron diet (D1 and D2) ingredients (g kg ) as reported by the pellet manufacturer (Mike Hoxey, Glen Forrest Stockfeeders Pty Ltd, Perth, Western Australia)

Dehulled lupins Dicalcium phosphate 1 Fish meal 65 Fish oil Fish premix Lecithin Limestone Maize Oat flour Shrimp meal Soyabean meal (full fat) Spirulina Vitamin C WA pilchard (dried) –1

–1

D1

D2

250.0 5.0 180.0 20.0 1.0 5.0 10.0 100.0 288.8 100.0 30.0 10.0 0.2 –

250.0 5.0 – – 1.0 5.0 10.0 100.0 288.8 100.0 30.0 10.0 0.2 200.0

–1

640 g kg protein, 100 g kg fat, 50 g kg NaCl, 94/95% egg white analogous.

rated in a dehydrator under 60°C. All stable pellets remained in their original form for the 20-h period while unstable pellets disintegrated when handled with tweezers after 3 min of water immersion or when left undisturbed for 5 min of water immersion. Marron of mixed parentage were provided by a commercial farm in central west Western Australia. Mean (± SE) initial weight of 0 1 marron was 11.5 ± 0.3 g and mean initial specific growth rate (SGR, explained below), obtained in a semi-intensive farm, was 0.79 ± 0.01. Marron were randomly divided into 13 groups, and initial weighing showed no differences among the groups. Marron held in communal tanks (two groups; three replicates; n = 20 per repli–2 cate; density 5 individuals m ) were fed with stable and unstable diet D2. The remaining seven treatment groups (n = 18 per group; –2 density 25 individuals m ) were reared in the ICCS (Jussila & Evans 1996) and fed diets D1–D4 (Table 1) or were not fed. Marron in both systems were fed daily at a rate of 6.5% of body weight per week. Compartments and tanks were siphoned from organic waste once per week except for the unfed group. The unfed group’s compartments were not siphoned in order to evaluate the effect of natural food items production on growth in the ICCS. Growth was estimated as: SGR = (lnWf – lnWi) 3 100/t where Wf is the final weight (g), Wi is the initial weight and (g), t is the study period (d); weight increment at moult –1

Wm = (Wpost – Wpre) 3 100 Wpre

where Wpre is the premoult weight (g) and Wpost is the postmoult weight (g); and intermoult period length Tim = DMn – DMn–1 where DM is the date of moult and n is the moult number. The experiment lasted until all marron in the test groups had moulted at least twice (125 d). The unfed group marron moulted only once during the experiment.

© 1998 Blackwell Science Ltd Aquaculture Nutrition 4; 143–149

Pellet stability and marron growth Table 3 Water quality and productivity in the ICCS and communal tanks –1

DO (mg L ) Tank 1 Tank 2 ICCS

pH

a

Temp (°C) a

8.0 ± 0.2 a 7.9 ± 0.2 b 6.8 ± 0.2

8.5 ± 0.1 a,b 8.3 ± 0.1 b 8.0 ± 0.1

b

21.2 ± 0.2 b 21.8 ± 0.2 a 24.1 ± 0.3

21

Ca

–1

(mg L ) 1

10 1 10 1 10

–1

Hardness (mg L )

Food item production

73 ± 7 73 ± 7 60 ± 12

1.00 0.76 0.53

Means with different superscripts within the same column are significantly different. 1 One measurement.

Marron in the ICCS were individually weighed in the beginning, after 90 days and at the end of the study as well as 5 days after moult. A check for moults was conducted daily. Marron in the communal tanks were weighed at the beginning and at the end of the study. Hepatopancreatic indices were measured for 10 intermoult stage C4 marron in each group. Crayfish were dissected within 2 h after the experiment was terminated, hepatopancreata were removed, placed in a pre-tared foil cup and weighed. Whole hepatopancreata were dried at 80°C for 24 h and the dry weight measured. Results were expressed as wet hepatosomatic index –1

HIwet = Wwh 3 100 Wt

where Wwh is the weight of wet hepatopancreas (g) and Wt is the total weight of marron (g), dry hepatosomatic index HIdry = Wdh 3 100 Wt

Results Water quality parameters indicated optimal growth conditions for marron both in the ICCS and communal tanks (Holdich & Lowery 1988; Table 3), with the ICCS having a significantly lower mean DO and a significantly higher mean temperature than communal tanks. Sessile organism production in communal tank 2 was lower than that in communal tank 1. Sessile organism production in the ICCS was half that in the communal tanks (Table 3), differences being statistically significant after 43 d of immersion. Stable diet D1 had a greater rate of dry weight loss than stable diet D2 (Fig. 1a), and the difference was statistically significant after 10 min of immersion in water. Stable diet D1 dry weight loss was statistically significantly less than stable diets D3 or D4 from 20 min onwards and even after 20 h stable diet D1 had lost less than 17% of its dry weight. Stable diets D1, D2 and D3

–1

where Wdh is the weight of dry hepatopancreas (g) and Wt is the total weight of marron (g), and hepatopancreas moisture content –1

HM = (Wwh – Wdh) 3 100 Wwh

(Mannonen & Henttonen 1995; Jussila 1997a). Water temperature was checked daily, and dissolved oxygen –1 –1 (DO, mg L ) and pH twice per week. Total ammonia (mg L ) –1 and total hardness (mg L ) were analysed every second week and water calcium level once. Diatometers were used to analyse sessile organism production. A rack was provided with seven slides and the amount of sessile organisms was estimated as accumulated dry organic matter (g) on the slides. Diatometers were placed in the system for 6 weeks and the analyses were repeated twice. 1 Data were processed with SPSS/PC v5.0.1 and Examine, T-test, Mann-Whitney U-test, one-way ANOVA (least significant differences), and analyses of covariance (ANCONA) were used in statistical analyses. The P-value for statistical significance was 0.05. Results are expressed as mean ± SE unless otherwise indicated.

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Figure 1 Pellet leaching (dry weight loss,%) in time (h) in (a) waterstable diets and (b) unstable and stable diet D1.

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J. Jussila & L. H. Evans 1

Table 4 Growth parameters

Wm1 (%) ICCS D1 (stable) D1 (unstable) D2 (stable) D2 (unstable) D3 D4 Unfed group Communal tanks D2 (stable) D2 (unstable)

Wm2 (%)

a

Tim (d)

a

SGR

b

Survival (%)

a

43.2 ± 3.9 a 39.5 ± 3.4 b 35.2 ± 1.5 c 29.7 ± 1.4 b 38.7 ± 3.6 a 41.6 ± 2.8 c 30.3 ± 2.1

45.2 ± 1.7 b 37.1 ± 1.9 b 39.1 ± 1.8 b 37.1 ± 1.9 b 35.1 ± 2.2 b 34.3 ± 2.1 –

42.5 ± 3.4 a 55.4 ± 3.2 a 53.9 ± 3.4 a 57.4 ± 3.1 b 43.6 ± 2.7 a 58.1 ± 5.5 –

0.68 ± 0.03 b 0.58 ± 0.03 b 0.57 ± 0.04 b,c 0.54 ± 0.04 c 0.47 ± 0.02 b,c 0.54 ± 0.04 d 0.20 ± 0.02

– –

– –

– –

0.68 ± 0.01 b 0.59 ± 0.02

100.0 89.5 100.0 89.5 89.5 88.9 88.9

a

85.0 ± 5.0 90.0 ± 2.9

Means with different superscript within same column are significantly different (one-way ANOVA among ICCS groups; Mann–Whitney U-test between communal tank groups). 1 Wm is weight increment at moult, Tim is intermoult period length and SGR is specific growth rate in treatment groups.

remained in their original pelleted form and could be handled without disintegration after 20 h of immersion, while diet D4 tended to disintegrate within 4 h of immersion. Stable diet D1 lost statistically significantly less weight than unstable diet D1 (Fig. 1b), the difference being 5% for the first 3 h and up to 10% after 20 h between the diets. Our observations showed that marron ignored pellets after they had broken up. Marron handled and ingested the intact stable pellets, and also ingested unstable pellets for as long as they stayed in form of a pellet. Unidentified fungus grew on the surface of the fine particle remains of unstable pellets within 24 h of immersion. Marron fed with stable diets D1 or D2 grew faster than marron fed the corresponding unstable diets, both in the ICCS and the semi-intensive rearing system (Table 4) with only minor differences in D2 dietary treatment. The improved growth rate was a combination of greater weight gain at moult and shorter intermoult period. Marron, reared in the ICCS and fed with stable diet

D1 had a significantly higher SGR than marron fed with stable diet D2. The D4 dietary treatment group had a similar SGR compared with groups fed with unstable diets D1 or D2. Differences in SGR among ICCS-reared groups were significant after the influence of initial weight was eliminated with ANCOVA and the model explained 63% of the variation in SGR. Diet D3, which was high in protein and crude fat (Table 1), produced a short intermoult period and an intermediate weight gain at moult compared with the low crude fat fish diet (D4). Survival was high in every treatment group. Marron reared in the ICCS lost natural dark brown carapace pigmentation in every group except the unfed group, with more severe pigmentation losses occurring in the groups fed with commercial marron diets. The colour typically changed to a bright light-blue pigment which initiated from lateral parts of exoskeleton. Marron reared in communal tanks and the unfed group showed no changes in carapace pigmentation.

Table 5 Hepatopancreatic indices in treatment groups Wet hepatosomatic index (%) ICCS D1 (stable) D1 (unstable) D2 (stable) D2 (unstable) D3 D4 Unfed group Communal tanks D2 (stable) D2 (unstable)

Dry hepatosomatic index (%)

c,b

1.7 ± 0.1 b 1.6 ± 0.1 b 1.7 ± 0.2 b 1.6 ± 0.1 a 2.1 ± 0.1 b 1.6 ± 0.2 c 0.3 ± 0.05

a

2.3 ± 0.1 a 2.5 ± 0.1

5.1 ± 0.2 b 5.4 ± 0.2 a,b 5.7 ± 0.4 a 5.9 ± 0.2 a 6.0 ± 0.2 c 4.5 ± 0.2 d 1.8 ± 0.1 5.8 ± 0.1 a 6.0 ± 0.2

Hepatopancreas water content (%)

b

66.6 ± 1.4 b,c,d 69.3 ± 1.8 b,c 70.0 ± 1.4 b 73.0 ± 1.1 d 65.2 ± 2.3 c,d 66.0 ± 2.6 a 83.7 ± 1.4

a

60.4 ± 0.9 f 58.0 ± 1.1

Means in the same column with different superscripts are significantly different (one-way communal tank groups).

c,d

e

ANOVA

among ICCS groups; T-test between

© 1998 Blackwell Science Ltd Aquaculture Nutrition 4; 143–149

Pellet stability and marron growth Groups in the communal tanks had highest wet and dry hepatosomatic indices and lowest moisture content in the hepatopancreata (Table 5). The unfed group had lowest hepatosomatic indices and also the hepatopancreata with the highest moisture content. The unstable diets tended to be associated with higher moisture contents of the hepatopancreata compared with those obtained with corresponding stable diet formulation and this difference was significant with respect to diet D2 in communal tanks (Table 5). The high protein and lipid diet, D3, yielded the highest hepatosomatic indices and lowest moisture content of hepatopancreata of all diets tested in the ICCS and gave results similar to those obtained with diet D2 (stable and unstable) in the communal rearing system.

Discussion Stable diets D1 and D2 yielded shorter intermoult periods and higher weight gains at moult than the corresponding unstable diets, indicating the superiority of stable diets over unstable ones in both the ICCS and the semi-intensive communal system. Stable pellets are reported to be biologically efficient as crustacean diets and, furthermore, because of their high nutritional quality they are more cost effective (Goldblatt et al. 1980; Farmanfarmaian et al. 1982; Meyers 1991). Chen & Yenn (1992) found growth performance improvements similar to those reported in the present study for shrimp fed stable pellets, even though the difference in leaching between the tested diets was minor in their study. The difference in pellet dry weight loss between stable diets D1 and D2 (Fig. 1a) could partly explain the difference in growth between the groups fed these diets. The weight loss in stable diet D1 was even less than in commercial salmon pellets (diet D4), which were made using binders. It is also possible that the differences observed in growth performance between diets D1 and D2 resulted from the different sources of fish meal used in the formulation. The nutrient loss was not analysed, but the water-soluble vitamins could have been lost in both stable diets (Gadient & Schai 1994), because marron were handling the stable pellets up to 24 h after they were placed in the culture systems. The marron feeding behaviour, which resulted in crayfish ignoring the remains of disintegrated pellets in both intensive and semi-intensive culture systems, could have caused the slower growth obtained in the groups fed with unstable compared with stable diets D1 or D2. As a result of pellet disintegration, the amount of feed actually ingested could have been lower in the groups fed with unstable diets. In a study on spiny lobsters, food shortage retarded growth (Chittleborough 1975). The intermoult period was affected initially and the lobsters had the tendency to gain maximum weight at moult. In our study, both of the growth components

© 1998 Blackwell Science Ltd Aquaculture Nutrition 4; 143–149

were affected, resulting in substantial differences in the SGR among the treatment groups. Morrissy (1984) has reported a 52% weight increment at moult in marron reared under optimal conditions, while the highest level observed in this study was 45% in the stable diet D1 group. Growth of marron in the ICCS and communal tanks was poorer than that obtained in farm ponds (Jussila 1996). The slow growth obtained in the present study might be a result of too high densities or suboptimal conditions relative to water quality, physical environment or nutrition. Survival, however, was high in all treatment groups, demonstrating the partial suitability of the diets for marron nutrition. The growth performance of marron reared in the communal system was better than that obtained with animals fed with the same diets but reared in the ICCS. This difference may have been due to the differences in densities, or natural food organisms production in tanks, or both (Table 3). Crayfish production has been reported to be higher when feeding consists of a combination of pellets and pond-produced forage (D’Abramo & Robinson 1989; Avault & Brunson 1990), and Mitchell et al. (1995) reported that microbially enriched plant detritus is essential to polytrophic animals such as crayfish — it also gives better carapace pigmentation. Natural production in the pond systems can be partly substituted by pellet feeding, as shown by the switching to natural feeds when the feeding rate of pellets is reduced (Tidwell et al. 1995). Groups in the communal tanks had algae and zooplankton as natural diet supplements. These crayfish, unlike those reared in the ICCS, showed normal carapace pigmentation. Furthermore, better carapace pigmentation in groups fed with fish diets in this study indicated that these diets could be sufficient for carotenoid requirements. Carotenoid deficiency leads to changes in pigmentation and possibly inhibits growth in crustaceans (D’Abramo & Robinson 1989; Howell & Matthews 1991); carotenoids may have also other vital roles in nutrition and should be added to artificial feeds (Nelis et al. 1989). Marron reared intensively in a system that has high level of natural food items production (Jussila 1997a,b), had similar size, hepatopancreata, which were lower in water content than marron in this study. Therefore, nutritional variation in the ICCS may affect marron condition. Marron in the communal tanks had hepatopancreatic indices similar to those of marron in semiintensive farm ponds (Jussila 1997a,b), suggesting that food availability in the communal tanks did not affect growth in this study. Hepatopancreatic indices of marron fed stable and unstable forms of the same diets (D1 or D2) were not significantly different despite significant differences being demonstrated in growth responses. Similarly, marron reared in the communal tanks had hepatopancreatic indices similar to those reared in farm

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J. Jussila & L. H. Evans ponds (Jussila 1997a) even though the growth rates obtained in the tanks were significantly lower than those observed in pond culture. The results obtained for the D3 dietary treatment in the ICCS provide additional evidence of variable growth and condition factor responses to diet. The hepatopancreatic indices for this group suggested good condition while growth rate was poorest. The unfed group had significantly lower wet and dry hepatosomatic indices and a higher moisture content of hepatopancreata compared with the other treatment groups. These results indicate the poor nutritional status of the unfed crayfish, further shown by their lack of second moult and low SGR. Other workers have reported similar effects of food deprivation on hepatopancreatic indices in crayfish and prawns (Whyte et al. 1986; Schirf et al. 1987; Evans et al. 1992; McClain 1995a,b). These results suggest that growth rates in freshwater crayfish do not necessarily correlate directly with body condition, as measured by hepatopancreatic indices. Wet hepatosomatic indices and moisture content of hepatopancreata are likely to be affected by environmental stressors (Mannonen & Henttonen 1995), oogenesis (Lindqvist & Louekari 1975; Haefner & Spaargaren 1993) and nutrition (Lindqvist & Louekari 1975; Evans et al. 1992; McClain 1995a,b; Gu et al. 1996) causing changes in body water content, while dry hepatosomatic indices are likely to be affected by nutritional factors (Huner et al. 1990; Jussila 1997a). In addition, Jussila & Mannonen (1997) have shown that moisture content of the hepatopancreas is inversely related to total energy content. These findings demonstrate the need for further evaluation of hepatopancreatic indices as measures of freshwater crayfish condition, especially if they are to be used as indicators of the nutritional status in farmed crayfishes (Jussila 1997b). The costs of preparing stable pellets compared with unstable ones was negligible, because binders were not used and the stability was induced by the processing method similar to the previous pelleting technique. Thus, the benefits to growth shown in this study can be achieved in commercial farming without adding production cost. This study showed that marron growth in intensive and semiintensive systems was improved when crayfish were fed with water-stable pellets. It was also demonstrated that hepatopancreatic indices showed no difference between treatment groups with a significant difference in growth rate. Finally, communal rearing at low density resulted in the marron being in better condition than those reared in the ICCS at high density, partly because of lack of natural food items production in the ICCS.

Acknowledgements Lennu Mannonen (AKFD) provided reference pellets and the Department of Applied Tetrapiloktomy, The University of Kuopio,

gave necessary support. The authors thank Professor Bruce Phillips, Curtin University of Technology, Professor Jay V. Huner, University of Southwestern Louisiana, USA, and Professor Arnold Eversole, Clemson University, USA, for their comments and suggestions during preparation of this manuscript. This study was financed by TEKES (Helsinki, Finland) and the Marron Grower’s Association of Western Australia.

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