- Email: [email protected]
Size grading did not enhance growth, survival and production of marron (Cherax tenuimanus) in experimental cages
Aquaculture 195 Ž2001. 239–251 www.elsevier.nlrlocateraqua-online
Size grading did not enhance growth, survival and production of marron žCherax tenuimanus/ in experimental cages Jian G. Qin a,) , Tara Ingerson b,1, Michael C. Geddes c , Martin Kumar d , Stephen Clarke d a
School of Biological Sciences, Flinders UniÕersity, GPO Box 2100, Adelaide 5001 SA, Australia b Aquaculture Program, Primary Industries and Resources of South Australia, GPO Box 1625, Adelaide SA 5001, Australia c Department of EnÕironmental Biology, UniÕersity of Adelaide, Adelaide 5005 SA, Australia d Aquatic Sciences Centre, South Australia Research and DeÕelopment Institute, PO Box 120, Henley Beach SA 5022, Australia
Received 24 February 2000; received in revised form 18 September 2000; accepted 17 October 2000
Abstract The necessity for size grading prior to stocking in marron culture is not clear. In this study, production characteristics of marron of three size-graded groups Ž15.2, 78.3 and 157.6 g. and one mixed group were tested in 24 experimental cages Ž6 = 3 = 2 m. with six replicates for each treatment. After 258 days, mean weight of small marron in the graded group increased from 15.2 to 40.1 g, while small marron in the mixed group increased from 14.8 to 46.4 g. Mean weight of medium marron in the graded group increased from 78.3 to 129.5 g, while medium marron in the mixed group increased from 76.7 to 132.6 g. Mean weight of large marron in the graded group increased from 157.6 to 218.9 g, while the large marron in the mixed group increased from 165.3 to 223.7 g. Size grading of marron did not lead to improved growth. Marron survival rate was not improved by grading either. Instead, survival rate of medium and large individuals was significantly greater in the mixed group than in the graded group. Size specific growth rates were size-dependent and small marron grew faster than either medium or large individuals. The sequence of standing biomass of different sized groups at harvest was medium size Ž3080 kgrha. ) mixed size Ž2941 kgrha. ) mall size Ž2482 kgrha. ) large size Ž2037 kgrha.. The
)
Corresponding author. Tel.: q61-8-8201-3045; fax: q61-8-8201-3015. E-mail address: [email protected] ŽJ.G. Qin.. 1 Research program manager.
0044-8486r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 4 - 8 4 8 6 Ž 0 0 . 0 0 5 5 4 - 8
240
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
sequence of net production of different sized groups was small size Ž1374 kgrha. ) mixed size Ž1042 kgrha. ) medium size Ž756 kgrha. ) large size Žy275kgrha.. Marron size grading during growout seems to be an unnecessary operation to improve the growth and survival. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Size grading; Growth; Survival; Production; Marron; Cages
1. Introduction The marron Ž Cherax tenuimanus. is a large, long-lived freshwater crayfish native to streams of southwestern Australia. It has attracted considerable aquaculture interest ŽAiken, 1988; Holdich, 1993.. As marron farming expands, there has been greater emphasis on optimisation of production. A major problem facing the commercial culture of marron is the variation of production and unpredictable survival during growout ŽMorrissy et al., 1990.. Research on marron aquaculture in the past 5 years has focussed on the following areas: Ž1. nutrition ŽTsvetnenko et al., 1995; Jussila and Evans, 1998.; Ž2. density-dependent growth ŽMorrissy et al., 1995; O’Brien, 1995; Whisson, 1995; Fotedar et al., 1997, 1998.; Ž3. polyculture with finfish ŽWhisson, 1997.; and Ž4. intensive culture in tanks ŽJussila and Evans, 1996.. However, no experimental study has been conducted to evaluate the impact of size grading prior to stocking on the growth and survival of marron during growout. Size grading in finfish can be an important strategy to improve growth and survival of stunted individuals, making sufficient resources available for individuals of different sizes ŽGunnes, 1976.. Because size grading is a tedious procedure and labour intensive, it is necessary to evaluate it before being applied to marron farming. Positive benefits of size grading have been repeatedly demonstrated in the culture of many finfish species ŽBaardvik and Jobling, 1990; Popper et al., 1992; Kamstra, 1993; Sunde et al., 1998.. The idea behind size grading is to separate small and large individuals from each other to avoid potentially negative effects of social interactions. Suggested mechanisms for the negative impact of larger fish on smaller ones include cannibalism ŽQin and Fast, 1996., direct competition for food ŽMagnuson, 1962. and reduced appetite of smaller individuals by the interference of larger ones ŽJobling and Wandsvik, 1983.. Competition for food seems to be particularly important in governing growth ŽJobling and Koskela, 1996.. By removing larger individuals, smaller individuals avoid the negative effects of a dominance hierarchy and may achieve higher growth rates ŽWallace and Kolbeinshavn, 1988.. Although size grading is not common in crustacean culture, some studies have evaluated the potential for increasing yield by size grading prior to stocking. Karplus et al. Ž1987. graded freshwater prawns into three-size groups Župper 32%, middle 45% and lower 23%., and found that, although the three groups differed in mean weight, the income from the graded groups did not differ from that of the ungraded group. Daniels and D’Abramo Ž1994. divided post-larvae of freshwater prawn into graded and ungraded groups and found that gross revenues in graded populations were 6–75% greater than that of ungraded population.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
241
Size grading is often a stressful procedure on the culture animal and the cost of grading can be high, especially if one also takes into consideration the risk of handling damage, disease outbreak, mortalities and growth reduction. At present, it is not clear the necessity of size grading at stocking in marron culture. The objective of this study was to investigate whether marron growth and survival can be improved by size grading prior to stocking in experimental cages. Marron were graded into three-size groups Žsmall, medium, and large. and additional marron were raised as a mixed group. We expected that improved growth in graded groups and poorer growth in the mixed group due to social interactions among animals of different size.
2. Materials and methods 2.1. Experimental cage structure Twenty-four cages Ž6 = 3 = 2m. were constructed in two rows within a pond Ž0.06 ha, 1.5 m deep. on a commercial farm on Kangaroo Island, South Australia. Each cage rose approximately 20 cm above the water level. The walls of the cages were constructed using 6 mm mesh. Each cage was supported by six timber posts spaced at 3-m intervals. A collar made from 90 mm PVC pipe was bolted to the top of the timber posts to prevent marron from climbing out of the cages. Marron had full access to the natural pond bottom in each cage. A platform was constructed between the two rows of cages, on which water quality monitoring, feeding and harvesting could be conducted. The pond was filled, and then was left to settle for a month before the experiment commenced. 2.2. Experimental design and protocols Marron were harvested from a single farm pond located on Kangaroo Island and stored in a plastic tank continuously overflowed with fresh water. Four treatments of different marron sizes were used: Ž1. small size Ž10–20 g, X s 15.2 g, CV s 47.3%, n s 756. stocked at 7rm2 ; Ž2. medium size Ž75–80 g, X s 78.3 g, CV s 19.1%, n s 324. stocked at 3rm2 ; Ž3. large size Ž150g–160 g, X s 157.6 g, CV s 15.3%, n s 163. stocked at 1.5rm 2 ; and Ž4. mixed size stocked with of 3.8 animalsrm2 , consisting of 2.3 small marronrm2 , 1 medium marronrm2 and 0.5 large marronrm2 . In the mixed group, animals of each size Žsmall, medium or large. were stocked as 1r3 of their density in the graded culture. The stocking biomasses in graded small, medium, large marron and mix-sized marron were 106, 235, 236 and 192 grm2 , respectively, which are similar to the densities used in commercial marron culture in ponds. The reason for using low stocking biomass for small marron was from consideration of their fast growth and frequent moulting rate. Each treatment consisted of six replicates and was randomly assigned to one of the 24 cages. Marron were hand-graded by weighing to the nearest 0.01 g using Mettler electronic scales ŽModel 460.. Each live marron was blotted with water absorbent paper before they were weighed. Vernier calipers were used to measure the orbit to carapace length
242
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
ŽOCL. to the nearest 0.1 mm. This was taken from the stem of the eyestalk to the mid-posterior edge of the carapace. Marron were sorted into different size classes and held within a holding tank until required. Both graded and mixed marron were fed with lupins Ž28% crude protein, 5% lipid, 12% fibre, 2% ash, 8% moisture and 45% carbohydrate. at 3% body weight twice weekly. Then, after 4 months, the feeding frequency was reduced to once a week with the same amount of feed. Feed was evenly distributed in the cage in the morning. The experimental cages were aerated with a single airlift unit shared by four adjacent cages. Harvest of marron in all cages occurred after a rearing period of 258 days ŽOctober 1, 1998–June 15, 1999.. The pond was equipped with a data logger ŽTPS 90-FL Field Lab. which recorded dissolved oxygen, temperature, and salinity at 2-h intervals. The probes measuring each parameter were located in the middle of the research pond, approximately 10 cm above the bottom. 2.3. Data analysis At the termination of the experiment, the research pond was drained in the morning. All marron collected from each cage were separately weighed to the nearest 0.01 g and measured to the nearest 0.1 mm. Survival was estimated based on the numbers stocked and harvested. Specific growth rate ŽSGR. was calculated according to the equation: SGR s 100ŽlnW2 y lnW1 .rŽ t 2 y t 1 ., where W2 is wet weight Žg. at time t 2 Ži.e. day 258. and W1 is the wet weight at time t 1 Ži.e. day 1.. Standing biomass was the total wet weight at harvest, while net production was calculated by subtracting the initial biomass from the final biomass. Weight frequency distributions, based on the measurements taken at the time of stocking and at harvesting, were analysed by pooling all the data of the same treatment Ži.e. from six replicates.. In mixed size cages, to distinguish the animals in each size category, small marron were left tail clipped, medium marron were right tail clipped, but no tails were clipped for large marron before stocking. At harvest, although marron had moulted, the tail clips could easily be distinguished. The small and medium marron held in the graded cages were also tail clipped to ensure that the difference in growth and survival in the graded or mixed group was not caused by tail clipping. Descriptive statistics such as means, and coefficient of variation ŽCV. were computed from the raw data. Analysis of variance and multiple comparison were used to evaluate the effect of size grading on carapace length, body weight, specific growth rate, standing biomass, net production and survival rate. All statistical tests were performed with General Linear Procedure ŽSAS, 1988..
3. Results During the experimental period, water temperature averaged 17.9 " 4.48C Žmean " s.d... From early October 1998, temperature gradually increased and reached the maximum Ž27.48C. in early December, then started to decline and reached the lowest point Ž7.48C. in mid June 1999 ŽFig. 1.. The average dissolved oxygen ŽDO. was 7.3 " 1.0 mgrl Žmean " s.d.. and diel fluctuation of DO was clearly observed in the
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
243
Fig. 1. Fluctuations of temperature, dissolved oxygen and salinity from October 1, 1998 to June 15, 1999 in the pond where the experimental cages were located.
experimental cages ŽFig. 1.. Maximum DO occurred in mid June Ž12.0 mgrl. while minimum DO was observed in early February Ž3.7 mgrl.. Salinity ranged from 0.61‰ to 0.91‰ and averaged 0.78 " 0.07‰ Žmean " s.d., Fig. 1.. The decline of salinity in mid January was due to bore water addition into the pond. Initial OCL measurements of the small, medium and large marron between graded and mixed groups were not significantly different Ž P ) 0.25, Fig. 2a.. Final OCL values of the small and large marron in the mixed group were significantly greater than those in the graded groups Ž P - 0.04, Fig. 2b.. For small and medium marron, the initial or final
244
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
body weight between graded and mixed groups was not significantly different Ž P ) 0.80, Fig. 2c and d.. For large marron, the initial and final weights in the graded culture were significantly smaller than those in the mixed culture Ž P - 0.04., but the initial weight difference was 3.8%, while the final difference increased to 5.3%, indicating that the marron in the mixed group gained more weight than in the graded group. A trend suggested that the specific growth rates of small, medium and large marron in the mixed group were greater than those in the graded group, although the difference was not significant Ž P ) 0.15, Fig. 2e.. Survival rate did not differ in small marron between the graded and mixed groups Ž P ) 0.90, Fig. 2f.. The survival rate of medium
Fig. 2. Growth characteristics of small, medium and large marron in graded and mixed culture conditions. Ža. initial orbit carapace length; Žb. final orbit carapace length; Žc. initial body weight; Žd. final body weight; Že. specific growth rate; Žf. survival rate; Žg. standing biomass; and Žh. net production. The capped error bars represent standard error of mean Žmean"s.e... Figures a–f: blank bars represent graded groups and cross-line bars represent mixed groups. Figures g–h: blank bars represent initial standing biomass and cross-line bars represent final biomass or net production.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
245
Fig. 2 Ž continued ..
marron in the mixed group was slightly greater than that in the graded group Ž P ) 0.18., while the survival rate of large marron in the mixed group was significantly greater than that in the graded group Ž P - 0.003.. Total standing biomass of small and medium marron at harvest was increased by 124% and 32.5%, respectively, while the final standing biomass of large marron was reduced by 11.9% ŽFig. 2g.. In the mixed group, the total standing biomass at harvest was increased by 54.9%. The sequence of standing biomass of different size groups at harvest was medium size Ž3080 kgrha. ) mixed size Ž2941 kgrha. ) small size Ž2482 kgrha. ) large size Ž2037 kgrha.. The sequence of net production in different grading groups was small size Ž1374 kgrha. ) mixed size Ž1042 kgrha. ) medium size Ž756 kgrha. ) large size Žy275 kgrha. ŽFig. 2h.. In the small size group, individuals weighing greater than 10, 20 and 25 g accounted for 72.3%, 27.4%, and 9.0%, respectively ŽFig. 3a.. At harvest, individuals weighing greater than 30, 40 and 60 g accounted for 72.7%, 29.1% and 10.3%, respectively. In the
246
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
mixed group, individuals weighing greater than 10, 20 and 25 g accounted for 82.3%, 16.1%, and 4.3%, respectively ŽFig. 3d.. At harvest individuals weighing greater than 30, 40 and 60 g accounted for 87.2%, 62.0% and 16.2%, respectively. In the medium size group, individuals weighing greater than 70, 85 and 100 g accounted for 68.2%, 31.2%, and 8.6%, respectively ŽFig. 3b.. At harvest, individuals
Fig. 3. Comparison of initial Ždotted line. and final Žsolid line. weight frequency distributions of small, medium, and large marron in graded Ža, b and c. and mixed Žd, e and f. groups.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
247
Fig. 3 Ž continued ..
with weight greater than 110, 140, and 165 g accounted for 74.9%, 31.5% and 10.4%, respectively. In the mixed group, individuals weighing greater than 70, 85 and 100 g accounted for 58.6%, 29.7%, and 9.0%, respectively ŽFig. 3e.. At harvest, individuals weighing greater than 110, 140 and 165 g accounted for 71.6%, 36.6% and 14.5%, respectively.
248
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
In the large size group, individuals weighing greater than 140, 170 and 190 g accounted for 71.8%, 31.3%, and 10.4%, respectively ŽFig. 3c.. At harvest, individuals weighing greater than 195, 230, and 275 g accounted for 72.0%, 32.0% and 10.0%, respectively. In the mixed group, individuals weighing greater than 140, 170 and 190 g accounted for 78.9%, 42.1%, and 14.0%, respectively ŽFig. 3f.. At harvest, individuals weighing greater than 195, 230, and 275 g accounted for 80.0%, 48.9% and 17.8%, respectively.
4. Discussion Size-related dominance hierarchies, resulting from aggressive behaviour, have been well documented in groups of freshwater crayfish ŽCopp 1986.. More complex social mechanisms exist in wild populations of mixed age groups of crayfish ŽMorgan and Momot, 1988.. Grading practice in freshwater prawns resulted in substantial increases in mean harvest weight and yield ŽMalecha, 1983; Daniels and D’Abramo, 1994.. Our study was the first to compare the effect of size grading of marron on production parameters. One might expect that marron would grow faster in graded groups than in a mixed group as size variation may result in dominance of larger individuals over smaller ones ŽKnights, 1987.. However, our study showed that the mean carapace length and weight of marron were not improved in any graded group compared with the mixed group, a finding that is contradictory to the main purpose of grading. The theory of competitive scramble and contest largely involves the assumptions about unequal sharing of resources ŽMay, 1989.. Perhaps the nocturnal feeding behaviour of marron minimises their interactions ŽMorrissy and Caputi, 1981.. Our data suggest that larger marron do not dominate their conspecifics and grading does not improve growth. From the point of view of commercial aquaculture, it is necessary to evaluate the production efficiency of different size groups by comparing the initial and final biomass. The biomass of small size marron increased from 1107 to 2482 kgrha, an increase of 124%. For medium size marron the increase was from 2324 to 3080 kgrha, or 32.5%. However, the initial biomass of large marron of 2312 kgrha reduced to 2037 kgrha at harvest due to high mortality, resulting in negative production. In the mixed group, the total biomass at harvest increased by 54.9%. This figure of net production again indicates that a greater size variation does not necessarily lead to reduced growth and suggests that there may be resource partitioning among marron of different size. Marron are omnivorous, but they depend heavily on microbially enriched plant detritus for basic sustenance ŽMills et al., 1994.. O’Brien Ž1995. suggested that large and small marron select different food sources from the environment. In the mixed group, food resource partitioning among different sized animals may reduce the degree of competition. Density-dependent survival of marron has been reported ŽFotedar et al., 1998; Whisson, 1995., but evidence of size-dependent survival of marron is not available. In our study, the survival rates of marron depended on animal size and the status of size grading. Small marron stocked at 7rm2 resulted in average growth of 40.1 g after 1 year with 84% survival, which was much higher than a similar study reported by Morrissy Ž1979. who found that a stocking rate of 5 Ž0 q age marron.rm2 achieved average
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
249
growth of 45 g after 1 year with 50% survival. The survival rate of small marron between graded and mixed culture was not different, but the survival of medium or large marron in the mixed groups was higher than that when graded. The survival rate of the large marron in the graded treatment was particularly low at 62%. Although the exact cause of high mortality of large individuals is not known, it may possibly be explained by the following reasons: Ž1. Low dissolved oxygen—according to Morrissy Ž1976., adult marron have a higher dissolved oxygen requirement Ž) 3.7 mgrl., and the low value of 3.5 mgrl detected in early February may have contributed to the high mortality of large marron; Ž2. Aggressive behaviour—adult marron are more aggressive and territorial than juveniles, and the agonistic behaviour may become serious as stocking density increases ŽMorrissy, 1976.; Ž3. Thermal stress—Rouse and Kartamulia Ž1992. reported that thermal stress Ž) 308C. could increase mortality during moulting especially for larger individuals. A high temperature of 27.48C was observed in deep water; however, the temperature in shallow water may have been much higher. Clearly, further research is needed to study size-dependent mortality in marron. So far no research has compared how the size variation may change during growout in marron. In this study, size variation of small marron decreased, but size variation of medium and large marron increased in both graded and mixed groups. In fish, however, an increase of size variation has been found in small fish but remain unchanged in large fish ŽWickins, 1985; Wallace and Kolbeinshavn, 1988.. The decrease in size variation in the smaller size of marron suggests that competition among small individuals is low, while the increase in size variation in medium and large groups suggests that competition increases as marron size increases. Doyle and Talbot Ž1986. hypothesised that the increase of size variation was not necessarily due to social interactions but rather was a consequence of differences between individuals in activity, habitat use and efficiency of using food resources. It is possible that the burrowing activity observed in some large marron ŽJohn Luckens, pers. comm.. may produce different growth rates between burrowing and non-burrowing individuals. Overall, results of this study demonstrated that size grading in marron culture did not lead to improved growth and survival. Growth of smaller individuals was not suppressed by the presence of larger individuals, thus pre-stocking grading may not be necessary in marron farming. Marron growers consider the production level of 1000 kgrha to be the profitable marker. Considering the growth and survival rates found in this study, the annual net production of small marron can readily reach 1000 kgrha. Although this production level can be achieved in mixed size culture, the relative proportion of small, medium and large marron in the mixed regime needs to be adjusted, depending on markets and pricing structure. Due to slower growth and high mortality of large individuals Ž) 200 g., net production of large marron was negative in our experiment. Therefore, further research needs to be conducted to investigate the reason of high mortality in large marron during growout. Acknowledgements Our thanks to Keith Keen, John Luckens ŽAustralian Freshwater Crayfish Growers Association—SA Branch. and Max Wingfield Žformer Freshwater Crayfish Industry
250
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
Development Officer PIRSA. for initiating this research project, to Ian Pratt for allocating his property and stock to carry out this experiment, to Tim Anderson and Josh Cinzio for running the routine experimental work. Thanks also to Coby Mathews, Di Leith, Bruce Beythien, Tony Owens and Sue Yeeles for assisting with data collection. This project was funded by Rural Industry Adjustment and Development Fund administered by the Rural Finance and Development Branch within PIRSA. Flinders University Research Board provided fund during the manuscript preparation.
References Aiken, D.E., 1988. Marron farming. World Aquacult. 19 Ž4., 14–17. Baardvik, B.M., Jobling, M., 1990. Effect of size-sorting on biomass gain and individual growth rates in Arctic charr, SalÕelinus alpinus L. Aquaculture 90, 11–16. Copp, N.H., 1986. Dominance hierarchies in the crayfish Procambarus clarkii ŽGirard, 1852. and the question of learned individual recognition ŽDecapoda, Astacidea.. Crustaceana 51, 9–24. Daniels, W.H., D’Abramo, L.R., 1994. Pond production characteristics of freshwater prawns Macrobrachium rosenbergii as influenced by the stocking of size-graded populations of juveniles. Aquaculture 122, 33–45. Doyle, R.W., Talbot, A.J., 1986. Artificial selection on growth and correlated selection on competitive behaviour in fish. Can. J. Fish. Aquat. Sci. 43, 1059–1064. Fotedar, R.K, Evans, L.H., Knott, B., 1997. The effect of dietary lipid level on the growth and survival of juvenile marron, Cherax tenuimanus ŽSmith.. Freshwater Crayfish 11, 417–427. Fotedar, R.K., Knott, B., Evans, L.H., 1998. Effect of stocking density on growth and survival of 3-month-old juvenile marron, Cherax tenuimanus, raised in a semi-controlled environment. J. Appl. Aquacult. 8 Ž4., 27–38. Gunnes, K., 1976. Effect of size grading young Atlantic salmon Ž Salmo salar . on subsequent growth. Aquaculture 9, 381–386. Holdich, D.M., 1993. A review of astaciculture: freshwater crayfish farming. Aquat. Living Resour. 6, 307–317. Jobling, M., Koskela, J., 1996. Inter-individual variations in feeding and growth in rainbow trout during restricted feeding and in a subsequent period of compensatory growth. J. Fish Biol. 49, 658–667. Jobling, M., Wandsvik, A., 1983. Effect of social interactions on growth rates and conversion efficiency of Arctic charr, SalÕelinus alpinus L. J. Fish Biol. 22, 577–584. Jussila, J., Evans, L.H., 1996. Impact of sump tank size on growth, survival, and production of marron, Cherax tenuimanus, in an intensive system. J. Appl. Aquacult. 6 Ž3., 23–31. Jussila, J., Evans, L.H., 1998. Growth and condition of marron Cherax tenuimanus fed pelleted diets of different stability. Aquacult. Nutr. 4 Ž3., 143–149. Kamstra, A., 1993. The effect of size grading on individual growth in eel, Anguilla anguilla, measured by individual marking. Aquaculture 112, 67–77. Karplus, I., Hulata, G., Wohlfarth, G.W., Halevy, A., 1987. The effect of size-grading juvenile Macrobrachium rosenbergii prior to stocking on their population structure and production in polyculture: 2. Dividing the population into three fractions. Aquaculture 62, 85–95. Knights, B., 1987. Agonistic behaviour and growth in the European eel, Anguilla anguilla L., in relation to warm-water aquaculture. J. Fish Biol. 31, 265–276. Magnuson, J.J., 1962. An analysis of aggressive behaviour, growth, and competition for food and space in medka Ž Oryzias latipes ŽPisces, Cyprinodontidae... Can. J. Zool. 40, 313–363. Malecha, S.R., 1983. Commercial pond production of the freshwater prawn, Macrobrachium rosenbergii in Hawaii. In: McVey, J.P., Moore, J.R. ŽEds.., CRC Handbook of Mariculture. Crustacean Aquaculture vol. I. CRC Press, Boca Raton, FL, pp. 231–259. May, R.M., 1989. Detecting density dependence in imaginary worlds. Nature ŽLondon. 338, 16–17.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
251
Mills, B.J., Morrissy, N.M., Huner, J.V., 1994. The Marron, Cherax tenuimanus. In: Huner, J.V. ŽEd.., Freshwater Crayfish Aquaculture in North America, Europe and Australia. Food Product Press, New York. Morgan, G.E., Momot, W.T., 1988. Exploitation of Orconectes Õirilis in northern climates: complementary of management options with self-regulatory life history strategies. Freshwater Crayfish 7, 69–80. Morrissy, N.M., 1976. Aquaculture of marron, Cherax tenuimanus, ŽSmith.: Part 2. Breeding and early rearing. Fish. Res. Bull. ŽWest. Aust. Mar. Res. Lab.. 17, 1–32. Morrissy, N.M., 1979. Experimental pond production of marron, Cherax tenuimanus ŽSmith. ŽDecapoda: Parastacidae.. Aquaculture 16, 319–344. Morrissy, N.M., Caputi, N., 1981. Use of catchability equations for population estimation of marron, Cherax tenuimanus ŽSmith. ŽDecapoda: Parastacidae.. Aust. J. Mar. Freshwater Res. 32, 213–225. Morrissy, N.M., Evans, L.H., Huner, J.V., 1990. Australian freshwater crayfish: aquaculture species. World Aquacult. 21 Ž2., 113–122. Morrissy, N.M., Walker, P., Moore, W., 1995. Predictive equations for managing semi-intensive grow-out of a freshwater crayfish Žmarron., Cherax tenuimanus ŽSmith 1912. ŽDecapoda: Parastacidae., on a commercial farm. Aquacult. Res. 26, 71–80. O’Brien, B.G., 1995. The natural diet of the freshwater crayfish Cherax tenuimanus ŽSmith 1912. ŽDecapoda: Parastacidae. as determined by gut content analysis. Freshwater Crayfish 10, 151–162. Popper, D.M., Golden, O., Shezifi, Y., 1992. Size distribution of juvenile gilthead sea bream Ž Sparus aurata., practical aspects. Is. J. Aquacult. 44, 147–148. Qin, J.G., Fast, A.W., 1996. Size and feed dependent cannibalism with juvenile snakehead Channa striatus. Aquaculture 144, 313–320. Rouse, D.B., Kartamulia, I., 1992. Influence of salinity and temperature on molting and survival of the Australian freshwater crayfish Ž Cherax tenuimanus.. Aquaculture 105, 47–52. SAS, 1988. User’s Guide: Statistics, Version 6.03, Cary, NC, 1022 pp. Sunde, L.M., Imsland, A.K., Folkvord, A., Stefansson, S.O., 1998. Effects of size grading on growth and survival of juvenile turbot at two temperatures. Aquacult. Int. 6, 19–32. Tsvetnenko, Y., Santelices, M., Evans, L.H., 1995. Effect of dietary protein levels and beta-carotene on growth of marron Cherax tenuimanus in an intensive culture system. Freshwater Crayfish 10, 611–622. Wallace, J.C., Kolbeinshavn, A.G., 1988. The effect of size grading on subsequent growth in fingerling Arctic charr, SalÕelinus alpinus ŽL... Aquaculture 73, 101–110. Whisson, G.J., 1995. Growth and survival as a function of density for marron Ž Cherax tenuimanus ŽSmith.. stocked in a recirculating system. Freshwater Crayfish 10, 630–637. Whisson, G.J., 1997. Investigating polyculture of marron, Cherax tenuimanus, with silver perch, Bidyanus bidyanus, and an aquatic macrophyte, Allisneria sp. Freshwater Crayfish 11, 577–586. Wickins, J.F., 1985. Growth variability in individually confined elvers, Anguilla anguilla ŽL... J. Fish Biol. 27, 469–478.
Size grading did not enhance growth, survival and production of marron žCherax tenuimanus/ in experimental cages Jian G. Qin a,) , Tara Ingerson b,1, Michael C. Geddes c , Martin Kumar d , Stephen Clarke d a
School of Biological Sciences, Flinders UniÕersity, GPO Box 2100, Adelaide 5001 SA, Australia b Aquaculture Program, Primary Industries and Resources of South Australia, GPO Box 1625, Adelaide SA 5001, Australia c Department of EnÕironmental Biology, UniÕersity of Adelaide, Adelaide 5005 SA, Australia d Aquatic Sciences Centre, South Australia Research and DeÕelopment Institute, PO Box 120, Henley Beach SA 5022, Australia
Received 24 February 2000; received in revised form 18 September 2000; accepted 17 October 2000
Abstract The necessity for size grading prior to stocking in marron culture is not clear. In this study, production characteristics of marron of three size-graded groups Ž15.2, 78.3 and 157.6 g. and one mixed group were tested in 24 experimental cages Ž6 = 3 = 2 m. with six replicates for each treatment. After 258 days, mean weight of small marron in the graded group increased from 15.2 to 40.1 g, while small marron in the mixed group increased from 14.8 to 46.4 g. Mean weight of medium marron in the graded group increased from 78.3 to 129.5 g, while medium marron in the mixed group increased from 76.7 to 132.6 g. Mean weight of large marron in the graded group increased from 157.6 to 218.9 g, while the large marron in the mixed group increased from 165.3 to 223.7 g. Size grading of marron did not lead to improved growth. Marron survival rate was not improved by grading either. Instead, survival rate of medium and large individuals was significantly greater in the mixed group than in the graded group. Size specific growth rates were size-dependent and small marron grew faster than either medium or large individuals. The sequence of standing biomass of different sized groups at harvest was medium size Ž3080 kgrha. ) mixed size Ž2941 kgrha. ) mall size Ž2482 kgrha. ) large size Ž2037 kgrha.. The
)
Corresponding author. Tel.: q61-8-8201-3045; fax: q61-8-8201-3015. E-mail address: [email protected] ŽJ.G. Qin.. 1 Research program manager.
0044-8486r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 4 - 8 4 8 6 Ž 0 0 . 0 0 5 5 4 - 8
240
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
sequence of net production of different sized groups was small size Ž1374 kgrha. ) mixed size Ž1042 kgrha. ) medium size Ž756 kgrha. ) large size Žy275kgrha.. Marron size grading during growout seems to be an unnecessary operation to improve the growth and survival. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Size grading; Growth; Survival; Production; Marron; Cages
1. Introduction The marron Ž Cherax tenuimanus. is a large, long-lived freshwater crayfish native to streams of southwestern Australia. It has attracted considerable aquaculture interest ŽAiken, 1988; Holdich, 1993.. As marron farming expands, there has been greater emphasis on optimisation of production. A major problem facing the commercial culture of marron is the variation of production and unpredictable survival during growout ŽMorrissy et al., 1990.. Research on marron aquaculture in the past 5 years has focussed on the following areas: Ž1. nutrition ŽTsvetnenko et al., 1995; Jussila and Evans, 1998.; Ž2. density-dependent growth ŽMorrissy et al., 1995; O’Brien, 1995; Whisson, 1995; Fotedar et al., 1997, 1998.; Ž3. polyculture with finfish ŽWhisson, 1997.; and Ž4. intensive culture in tanks ŽJussila and Evans, 1996.. However, no experimental study has been conducted to evaluate the impact of size grading prior to stocking on the growth and survival of marron during growout. Size grading in finfish can be an important strategy to improve growth and survival of stunted individuals, making sufficient resources available for individuals of different sizes ŽGunnes, 1976.. Because size grading is a tedious procedure and labour intensive, it is necessary to evaluate it before being applied to marron farming. Positive benefits of size grading have been repeatedly demonstrated in the culture of many finfish species ŽBaardvik and Jobling, 1990; Popper et al., 1992; Kamstra, 1993; Sunde et al., 1998.. The idea behind size grading is to separate small and large individuals from each other to avoid potentially negative effects of social interactions. Suggested mechanisms for the negative impact of larger fish on smaller ones include cannibalism ŽQin and Fast, 1996., direct competition for food ŽMagnuson, 1962. and reduced appetite of smaller individuals by the interference of larger ones ŽJobling and Wandsvik, 1983.. Competition for food seems to be particularly important in governing growth ŽJobling and Koskela, 1996.. By removing larger individuals, smaller individuals avoid the negative effects of a dominance hierarchy and may achieve higher growth rates ŽWallace and Kolbeinshavn, 1988.. Although size grading is not common in crustacean culture, some studies have evaluated the potential for increasing yield by size grading prior to stocking. Karplus et al. Ž1987. graded freshwater prawns into three-size groups Župper 32%, middle 45% and lower 23%., and found that, although the three groups differed in mean weight, the income from the graded groups did not differ from that of the ungraded group. Daniels and D’Abramo Ž1994. divided post-larvae of freshwater prawn into graded and ungraded groups and found that gross revenues in graded populations were 6–75% greater than that of ungraded population.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
241
Size grading is often a stressful procedure on the culture animal and the cost of grading can be high, especially if one also takes into consideration the risk of handling damage, disease outbreak, mortalities and growth reduction. At present, it is not clear the necessity of size grading at stocking in marron culture. The objective of this study was to investigate whether marron growth and survival can be improved by size grading prior to stocking in experimental cages. Marron were graded into three-size groups Žsmall, medium, and large. and additional marron were raised as a mixed group. We expected that improved growth in graded groups and poorer growth in the mixed group due to social interactions among animals of different size.
2. Materials and methods 2.1. Experimental cage structure Twenty-four cages Ž6 = 3 = 2m. were constructed in two rows within a pond Ž0.06 ha, 1.5 m deep. on a commercial farm on Kangaroo Island, South Australia. Each cage rose approximately 20 cm above the water level. The walls of the cages were constructed using 6 mm mesh. Each cage was supported by six timber posts spaced at 3-m intervals. A collar made from 90 mm PVC pipe was bolted to the top of the timber posts to prevent marron from climbing out of the cages. Marron had full access to the natural pond bottom in each cage. A platform was constructed between the two rows of cages, on which water quality monitoring, feeding and harvesting could be conducted. The pond was filled, and then was left to settle for a month before the experiment commenced. 2.2. Experimental design and protocols Marron were harvested from a single farm pond located on Kangaroo Island and stored in a plastic tank continuously overflowed with fresh water. Four treatments of different marron sizes were used: Ž1. small size Ž10–20 g, X s 15.2 g, CV s 47.3%, n s 756. stocked at 7rm2 ; Ž2. medium size Ž75–80 g, X s 78.3 g, CV s 19.1%, n s 324. stocked at 3rm2 ; Ž3. large size Ž150g–160 g, X s 157.6 g, CV s 15.3%, n s 163. stocked at 1.5rm 2 ; and Ž4. mixed size stocked with of 3.8 animalsrm2 , consisting of 2.3 small marronrm2 , 1 medium marronrm2 and 0.5 large marronrm2 . In the mixed group, animals of each size Žsmall, medium or large. were stocked as 1r3 of their density in the graded culture. The stocking biomasses in graded small, medium, large marron and mix-sized marron were 106, 235, 236 and 192 grm2 , respectively, which are similar to the densities used in commercial marron culture in ponds. The reason for using low stocking biomass for small marron was from consideration of their fast growth and frequent moulting rate. Each treatment consisted of six replicates and was randomly assigned to one of the 24 cages. Marron were hand-graded by weighing to the nearest 0.01 g using Mettler electronic scales ŽModel 460.. Each live marron was blotted with water absorbent paper before they were weighed. Vernier calipers were used to measure the orbit to carapace length
242
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
ŽOCL. to the nearest 0.1 mm. This was taken from the stem of the eyestalk to the mid-posterior edge of the carapace. Marron were sorted into different size classes and held within a holding tank until required. Both graded and mixed marron were fed with lupins Ž28% crude protein, 5% lipid, 12% fibre, 2% ash, 8% moisture and 45% carbohydrate. at 3% body weight twice weekly. Then, after 4 months, the feeding frequency was reduced to once a week with the same amount of feed. Feed was evenly distributed in the cage in the morning. The experimental cages were aerated with a single airlift unit shared by four adjacent cages. Harvest of marron in all cages occurred after a rearing period of 258 days ŽOctober 1, 1998–June 15, 1999.. The pond was equipped with a data logger ŽTPS 90-FL Field Lab. which recorded dissolved oxygen, temperature, and salinity at 2-h intervals. The probes measuring each parameter were located in the middle of the research pond, approximately 10 cm above the bottom. 2.3. Data analysis At the termination of the experiment, the research pond was drained in the morning. All marron collected from each cage were separately weighed to the nearest 0.01 g and measured to the nearest 0.1 mm. Survival was estimated based on the numbers stocked and harvested. Specific growth rate ŽSGR. was calculated according to the equation: SGR s 100ŽlnW2 y lnW1 .rŽ t 2 y t 1 ., where W2 is wet weight Žg. at time t 2 Ži.e. day 258. and W1 is the wet weight at time t 1 Ži.e. day 1.. Standing biomass was the total wet weight at harvest, while net production was calculated by subtracting the initial biomass from the final biomass. Weight frequency distributions, based on the measurements taken at the time of stocking and at harvesting, were analysed by pooling all the data of the same treatment Ži.e. from six replicates.. In mixed size cages, to distinguish the animals in each size category, small marron were left tail clipped, medium marron were right tail clipped, but no tails were clipped for large marron before stocking. At harvest, although marron had moulted, the tail clips could easily be distinguished. The small and medium marron held in the graded cages were also tail clipped to ensure that the difference in growth and survival in the graded or mixed group was not caused by tail clipping. Descriptive statistics such as means, and coefficient of variation ŽCV. were computed from the raw data. Analysis of variance and multiple comparison were used to evaluate the effect of size grading on carapace length, body weight, specific growth rate, standing biomass, net production and survival rate. All statistical tests were performed with General Linear Procedure ŽSAS, 1988..
3. Results During the experimental period, water temperature averaged 17.9 " 4.48C Žmean " s.d... From early October 1998, temperature gradually increased and reached the maximum Ž27.48C. in early December, then started to decline and reached the lowest point Ž7.48C. in mid June 1999 ŽFig. 1.. The average dissolved oxygen ŽDO. was 7.3 " 1.0 mgrl Žmean " s.d.. and diel fluctuation of DO was clearly observed in the
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
243
Fig. 1. Fluctuations of temperature, dissolved oxygen and salinity from October 1, 1998 to June 15, 1999 in the pond where the experimental cages were located.
experimental cages ŽFig. 1.. Maximum DO occurred in mid June Ž12.0 mgrl. while minimum DO was observed in early February Ž3.7 mgrl.. Salinity ranged from 0.61‰ to 0.91‰ and averaged 0.78 " 0.07‰ Žmean " s.d., Fig. 1.. The decline of salinity in mid January was due to bore water addition into the pond. Initial OCL measurements of the small, medium and large marron between graded and mixed groups were not significantly different Ž P ) 0.25, Fig. 2a.. Final OCL values of the small and large marron in the mixed group were significantly greater than those in the graded groups Ž P - 0.04, Fig. 2b.. For small and medium marron, the initial or final
244
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
body weight between graded and mixed groups was not significantly different Ž P ) 0.80, Fig. 2c and d.. For large marron, the initial and final weights in the graded culture were significantly smaller than those in the mixed culture Ž P - 0.04., but the initial weight difference was 3.8%, while the final difference increased to 5.3%, indicating that the marron in the mixed group gained more weight than in the graded group. A trend suggested that the specific growth rates of small, medium and large marron in the mixed group were greater than those in the graded group, although the difference was not significant Ž P ) 0.15, Fig. 2e.. Survival rate did not differ in small marron between the graded and mixed groups Ž P ) 0.90, Fig. 2f.. The survival rate of medium
Fig. 2. Growth characteristics of small, medium and large marron in graded and mixed culture conditions. Ža. initial orbit carapace length; Žb. final orbit carapace length; Žc. initial body weight; Žd. final body weight; Že. specific growth rate; Žf. survival rate; Žg. standing biomass; and Žh. net production. The capped error bars represent standard error of mean Žmean"s.e... Figures a–f: blank bars represent graded groups and cross-line bars represent mixed groups. Figures g–h: blank bars represent initial standing biomass and cross-line bars represent final biomass or net production.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
245
Fig. 2 Ž continued ..
marron in the mixed group was slightly greater than that in the graded group Ž P ) 0.18., while the survival rate of large marron in the mixed group was significantly greater than that in the graded group Ž P - 0.003.. Total standing biomass of small and medium marron at harvest was increased by 124% and 32.5%, respectively, while the final standing biomass of large marron was reduced by 11.9% ŽFig. 2g.. In the mixed group, the total standing biomass at harvest was increased by 54.9%. The sequence of standing biomass of different size groups at harvest was medium size Ž3080 kgrha. ) mixed size Ž2941 kgrha. ) small size Ž2482 kgrha. ) large size Ž2037 kgrha.. The sequence of net production in different grading groups was small size Ž1374 kgrha. ) mixed size Ž1042 kgrha. ) medium size Ž756 kgrha. ) large size Žy275 kgrha. ŽFig. 2h.. In the small size group, individuals weighing greater than 10, 20 and 25 g accounted for 72.3%, 27.4%, and 9.0%, respectively ŽFig. 3a.. At harvest, individuals weighing greater than 30, 40 and 60 g accounted for 72.7%, 29.1% and 10.3%, respectively. In the
246
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
mixed group, individuals weighing greater than 10, 20 and 25 g accounted for 82.3%, 16.1%, and 4.3%, respectively ŽFig. 3d.. At harvest individuals weighing greater than 30, 40 and 60 g accounted for 87.2%, 62.0% and 16.2%, respectively. In the medium size group, individuals weighing greater than 70, 85 and 100 g accounted for 68.2%, 31.2%, and 8.6%, respectively ŽFig. 3b.. At harvest, individuals
Fig. 3. Comparison of initial Ždotted line. and final Žsolid line. weight frequency distributions of small, medium, and large marron in graded Ža, b and c. and mixed Žd, e and f. groups.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
247
Fig. 3 Ž continued ..
with weight greater than 110, 140, and 165 g accounted for 74.9%, 31.5% and 10.4%, respectively. In the mixed group, individuals weighing greater than 70, 85 and 100 g accounted for 58.6%, 29.7%, and 9.0%, respectively ŽFig. 3e.. At harvest, individuals weighing greater than 110, 140 and 165 g accounted for 71.6%, 36.6% and 14.5%, respectively.
248
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
In the large size group, individuals weighing greater than 140, 170 and 190 g accounted for 71.8%, 31.3%, and 10.4%, respectively ŽFig. 3c.. At harvest, individuals weighing greater than 195, 230, and 275 g accounted for 72.0%, 32.0% and 10.0%, respectively. In the mixed group, individuals weighing greater than 140, 170 and 190 g accounted for 78.9%, 42.1%, and 14.0%, respectively ŽFig. 3f.. At harvest, individuals weighing greater than 195, 230, and 275 g accounted for 80.0%, 48.9% and 17.8%, respectively.
4. Discussion Size-related dominance hierarchies, resulting from aggressive behaviour, have been well documented in groups of freshwater crayfish ŽCopp 1986.. More complex social mechanisms exist in wild populations of mixed age groups of crayfish ŽMorgan and Momot, 1988.. Grading practice in freshwater prawns resulted in substantial increases in mean harvest weight and yield ŽMalecha, 1983; Daniels and D’Abramo, 1994.. Our study was the first to compare the effect of size grading of marron on production parameters. One might expect that marron would grow faster in graded groups than in a mixed group as size variation may result in dominance of larger individuals over smaller ones ŽKnights, 1987.. However, our study showed that the mean carapace length and weight of marron were not improved in any graded group compared with the mixed group, a finding that is contradictory to the main purpose of grading. The theory of competitive scramble and contest largely involves the assumptions about unequal sharing of resources ŽMay, 1989.. Perhaps the nocturnal feeding behaviour of marron minimises their interactions ŽMorrissy and Caputi, 1981.. Our data suggest that larger marron do not dominate their conspecifics and grading does not improve growth. From the point of view of commercial aquaculture, it is necessary to evaluate the production efficiency of different size groups by comparing the initial and final biomass. The biomass of small size marron increased from 1107 to 2482 kgrha, an increase of 124%. For medium size marron the increase was from 2324 to 3080 kgrha, or 32.5%. However, the initial biomass of large marron of 2312 kgrha reduced to 2037 kgrha at harvest due to high mortality, resulting in negative production. In the mixed group, the total biomass at harvest increased by 54.9%. This figure of net production again indicates that a greater size variation does not necessarily lead to reduced growth and suggests that there may be resource partitioning among marron of different size. Marron are omnivorous, but they depend heavily on microbially enriched plant detritus for basic sustenance ŽMills et al., 1994.. O’Brien Ž1995. suggested that large and small marron select different food sources from the environment. In the mixed group, food resource partitioning among different sized animals may reduce the degree of competition. Density-dependent survival of marron has been reported ŽFotedar et al., 1998; Whisson, 1995., but evidence of size-dependent survival of marron is not available. In our study, the survival rates of marron depended on animal size and the status of size grading. Small marron stocked at 7rm2 resulted in average growth of 40.1 g after 1 year with 84% survival, which was much higher than a similar study reported by Morrissy Ž1979. who found that a stocking rate of 5 Ž0 q age marron.rm2 achieved average
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
249
growth of 45 g after 1 year with 50% survival. The survival rate of small marron between graded and mixed culture was not different, but the survival of medium or large marron in the mixed groups was higher than that when graded. The survival rate of the large marron in the graded treatment was particularly low at 62%. Although the exact cause of high mortality of large individuals is not known, it may possibly be explained by the following reasons: Ž1. Low dissolved oxygen—according to Morrissy Ž1976., adult marron have a higher dissolved oxygen requirement Ž) 3.7 mgrl., and the low value of 3.5 mgrl detected in early February may have contributed to the high mortality of large marron; Ž2. Aggressive behaviour—adult marron are more aggressive and territorial than juveniles, and the agonistic behaviour may become serious as stocking density increases ŽMorrissy, 1976.; Ž3. Thermal stress—Rouse and Kartamulia Ž1992. reported that thermal stress Ž) 308C. could increase mortality during moulting especially for larger individuals. A high temperature of 27.48C was observed in deep water; however, the temperature in shallow water may have been much higher. Clearly, further research is needed to study size-dependent mortality in marron. So far no research has compared how the size variation may change during growout in marron. In this study, size variation of small marron decreased, but size variation of medium and large marron increased in both graded and mixed groups. In fish, however, an increase of size variation has been found in small fish but remain unchanged in large fish ŽWickins, 1985; Wallace and Kolbeinshavn, 1988.. The decrease in size variation in the smaller size of marron suggests that competition among small individuals is low, while the increase in size variation in medium and large groups suggests that competition increases as marron size increases. Doyle and Talbot Ž1986. hypothesised that the increase of size variation was not necessarily due to social interactions but rather was a consequence of differences between individuals in activity, habitat use and efficiency of using food resources. It is possible that the burrowing activity observed in some large marron ŽJohn Luckens, pers. comm.. may produce different growth rates between burrowing and non-burrowing individuals. Overall, results of this study demonstrated that size grading in marron culture did not lead to improved growth and survival. Growth of smaller individuals was not suppressed by the presence of larger individuals, thus pre-stocking grading may not be necessary in marron farming. Marron growers consider the production level of 1000 kgrha to be the profitable marker. Considering the growth and survival rates found in this study, the annual net production of small marron can readily reach 1000 kgrha. Although this production level can be achieved in mixed size culture, the relative proportion of small, medium and large marron in the mixed regime needs to be adjusted, depending on markets and pricing structure. Due to slower growth and high mortality of large individuals Ž) 200 g., net production of large marron was negative in our experiment. Therefore, further research needs to be conducted to investigate the reason of high mortality in large marron during growout. Acknowledgements Our thanks to Keith Keen, John Luckens ŽAustralian Freshwater Crayfish Growers Association—SA Branch. and Max Wingfield Žformer Freshwater Crayfish Industry
250
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
Development Officer PIRSA. for initiating this research project, to Ian Pratt for allocating his property and stock to carry out this experiment, to Tim Anderson and Josh Cinzio for running the routine experimental work. Thanks also to Coby Mathews, Di Leith, Bruce Beythien, Tony Owens and Sue Yeeles for assisting with data collection. This project was funded by Rural Industry Adjustment and Development Fund administered by the Rural Finance and Development Branch within PIRSA. Flinders University Research Board provided fund during the manuscript preparation.
References Aiken, D.E., 1988. Marron farming. World Aquacult. 19 Ž4., 14–17. Baardvik, B.M., Jobling, M., 1990. Effect of size-sorting on biomass gain and individual growth rates in Arctic charr, SalÕelinus alpinus L. Aquaculture 90, 11–16. Copp, N.H., 1986. Dominance hierarchies in the crayfish Procambarus clarkii ŽGirard, 1852. and the question of learned individual recognition ŽDecapoda, Astacidea.. Crustaceana 51, 9–24. Daniels, W.H., D’Abramo, L.R., 1994. Pond production characteristics of freshwater prawns Macrobrachium rosenbergii as influenced by the stocking of size-graded populations of juveniles. Aquaculture 122, 33–45. Doyle, R.W., Talbot, A.J., 1986. Artificial selection on growth and correlated selection on competitive behaviour in fish. Can. J. Fish. Aquat. Sci. 43, 1059–1064. Fotedar, R.K, Evans, L.H., Knott, B., 1997. The effect of dietary lipid level on the growth and survival of juvenile marron, Cherax tenuimanus ŽSmith.. Freshwater Crayfish 11, 417–427. Fotedar, R.K., Knott, B., Evans, L.H., 1998. Effect of stocking density on growth and survival of 3-month-old juvenile marron, Cherax tenuimanus, raised in a semi-controlled environment. J. Appl. Aquacult. 8 Ž4., 27–38. Gunnes, K., 1976. Effect of size grading young Atlantic salmon Ž Salmo salar . on subsequent growth. Aquaculture 9, 381–386. Holdich, D.M., 1993. A review of astaciculture: freshwater crayfish farming. Aquat. Living Resour. 6, 307–317. Jobling, M., Koskela, J., 1996. Inter-individual variations in feeding and growth in rainbow trout during restricted feeding and in a subsequent period of compensatory growth. J. Fish Biol. 49, 658–667. Jobling, M., Wandsvik, A., 1983. Effect of social interactions on growth rates and conversion efficiency of Arctic charr, SalÕelinus alpinus L. J. Fish Biol. 22, 577–584. Jussila, J., Evans, L.H., 1996. Impact of sump tank size on growth, survival, and production of marron, Cherax tenuimanus, in an intensive system. J. Appl. Aquacult. 6 Ž3., 23–31. Jussila, J., Evans, L.H., 1998. Growth and condition of marron Cherax tenuimanus fed pelleted diets of different stability. Aquacult. Nutr. 4 Ž3., 143–149. Kamstra, A., 1993. The effect of size grading on individual growth in eel, Anguilla anguilla, measured by individual marking. Aquaculture 112, 67–77. Karplus, I., Hulata, G., Wohlfarth, G.W., Halevy, A., 1987. The effect of size-grading juvenile Macrobrachium rosenbergii prior to stocking on their population structure and production in polyculture: 2. Dividing the population into three fractions. Aquaculture 62, 85–95. Knights, B., 1987. Agonistic behaviour and growth in the European eel, Anguilla anguilla L., in relation to warm-water aquaculture. J. Fish Biol. 31, 265–276. Magnuson, J.J., 1962. An analysis of aggressive behaviour, growth, and competition for food and space in medka Ž Oryzias latipes ŽPisces, Cyprinodontidae... Can. J. Zool. 40, 313–363. Malecha, S.R., 1983. Commercial pond production of the freshwater prawn, Macrobrachium rosenbergii in Hawaii. In: McVey, J.P., Moore, J.R. ŽEds.., CRC Handbook of Mariculture. Crustacean Aquaculture vol. I. CRC Press, Boca Raton, FL, pp. 231–259. May, R.M., 1989. Detecting density dependence in imaginary worlds. Nature ŽLondon. 338, 16–17.
J.G. Qin et al.r Aquaculture 195 (2001) 239–251
251
Mills, B.J., Morrissy, N.M., Huner, J.V., 1994. The Marron, Cherax tenuimanus. In: Huner, J.V. ŽEd.., Freshwater Crayfish Aquaculture in North America, Europe and Australia. Food Product Press, New York. Morgan, G.E., Momot, W.T., 1988. Exploitation of Orconectes Õirilis in northern climates: complementary of management options with self-regulatory life history strategies. Freshwater Crayfish 7, 69–80. Morrissy, N.M., 1976. Aquaculture of marron, Cherax tenuimanus, ŽSmith.: Part 2. Breeding and early rearing. Fish. Res. Bull. ŽWest. Aust. Mar. Res. Lab.. 17, 1–32. Morrissy, N.M., 1979. Experimental pond production of marron, Cherax tenuimanus ŽSmith. ŽDecapoda: Parastacidae.. Aquaculture 16, 319–344. Morrissy, N.M., Caputi, N., 1981. Use of catchability equations for population estimation of marron, Cherax tenuimanus ŽSmith. ŽDecapoda: Parastacidae.. Aust. J. Mar. Freshwater Res. 32, 213–225. Morrissy, N.M., Evans, L.H., Huner, J.V., 1990. Australian freshwater crayfish: aquaculture species. World Aquacult. 21 Ž2., 113–122. Morrissy, N.M., Walker, P., Moore, W., 1995. Predictive equations for managing semi-intensive grow-out of a freshwater crayfish Žmarron., Cherax tenuimanus ŽSmith 1912. ŽDecapoda: Parastacidae., on a commercial farm. Aquacult. Res. 26, 71–80. O’Brien, B.G., 1995. The natural diet of the freshwater crayfish Cherax tenuimanus ŽSmith 1912. ŽDecapoda: Parastacidae. as determined by gut content analysis. Freshwater Crayfish 10, 151–162. Popper, D.M., Golden, O., Shezifi, Y., 1992. Size distribution of juvenile gilthead sea bream Ž Sparus aurata., practical aspects. Is. J. Aquacult. 44, 147–148. Qin, J.G., Fast, A.W., 1996. Size and feed dependent cannibalism with juvenile snakehead Channa striatus. Aquaculture 144, 313–320. Rouse, D.B., Kartamulia, I., 1992. Influence of salinity and temperature on molting and survival of the Australian freshwater crayfish Ž Cherax tenuimanus.. Aquaculture 105, 47–52. SAS, 1988. User’s Guide: Statistics, Version 6.03, Cary, NC, 1022 pp. Sunde, L.M., Imsland, A.K., Folkvord, A., Stefansson, S.O., 1998. Effects of size grading on growth and survival of juvenile turbot at two temperatures. Aquacult. Int. 6, 19–32. Tsvetnenko, Y., Santelices, M., Evans, L.H., 1995. Effect of dietary protein levels and beta-carotene on growth of marron Cherax tenuimanus in an intensive culture system. Freshwater Crayfish 10, 611–622. Wallace, J.C., Kolbeinshavn, A.G., 1988. The effect of size grading on subsequent growth in fingerling Arctic charr, SalÕelinus alpinus ŽL... Aquaculture 73, 101–110. Whisson, G.J., 1995. Growth and survival as a function of density for marron Ž Cherax tenuimanus ŽSmith.. stocked in a recirculating system. Freshwater Crayfish 10, 630–637. Whisson, G.J., 1997. Investigating polyculture of marron, Cherax tenuimanus, with silver perch, Bidyanus bidyanus, and an aquatic macrophyte, Allisneria sp. Freshwater Crayfish 11, 577–586. Wickins, J.F., 1985. Growth variability in individually confined elvers, Anguilla anguilla ŽL... J. Fish Biol. 27, 469–478.