www.elsevier.nlrlocateraqua-online
A comparison of mixed-sex vs. monosex growout
and different diets on the growth rate of freshwater
ž
/
crayfish Cherax albidus
C.S. Lawrence
), Y.W. Cheng, N.M. Morrissy, I.H. Williams
Fisheries WA, Research DiÕision, P.O. Box 20, North Beach, WA 6020, Australia
Accepted 7 November 1999
Abstract
Growth and density in freshwater crayfish are inversely related and this is compounded by
Ž .
uncontrolled reproduction in growout ponds. Growth rates of yabbies Cherax albidus were compared in monosex and mixed-sex populations using three feeding regimes to assess whether preventing reproduction in ponds and improving feed quantity or quality could reduce stunting. Male monosex populations grew on average 68% faster than female monosex populations and 53% faster than mixed-sex populations. Female yabbies in monosex culture grew 9% slower than
Ž . Ž .
males and females combined in mixed-sex 50:50 populations. Both males 17% and females
Ž31% in monosex culture grew faster than males and females in mixed-sex culture. Stocking.
ponds with only male yabbies resulted in a 70% greater gross value of animals produced than normal mixed-sex production. While growth in monosex and mixed-sex populations was improved
Ž y2 y1.
by either increasing feed rates of lupins 2.5 to 5 g m week or using a formulated diet, male monosex populations still grew faster.q2000 Elsevier Science B.V. All rights reserved.
Keywords: Cherax albidus; Monosex; Diet; Growth; Crayfish; Yabby
1. Introduction
Ž .
Yabbies Cherax albidus are indigenous to central and eastern Australia, and have Ž
received considerable aquaculture interest Smallridge, 1990; Brown et al., 1997; .
Lawrence, 1998 . Although some yabbies are produced from ponds on purpose-built
)Corresponding author. Tel.:q61-08-9246-8415; fax:q61-08-9447-3062.
Ž .
E-mail address: clawrence@fish.wa.gov.au C.S. Lawrence .
0044-8486r00r$ - see front matterq2000 Elsevier Science B.V. All rights reserved.
Ž .
farms, the vast majority of commercial yabby production in Australia comes from trapping self sustaining, multigenerational populations of essentially wild yabbies out of water storage dams on farms. Poor growth of yabbies reduces the value of farm dam crayfish production, since the price received per kilogram for crayfish is directly related
Ž .
to individual weight of the animals Lawrence, 1998 .
Several mechanisms, other than direct food supply, may limit the growth of crayfish at increased densities. These include increased energy requirements to compete for food,
Ž
or diversion of energy from somatic growth to reproductive effort i.e., competition for .
mates and production of gametes . Female crayfish develop large yolky eggs, and the energetic cost of this reproductive effort can be observed in female yabbies, which grow at the same rate as males until sexual maturity at about 20 g, after which their growth
Ž .
slows markedly relative to males Woodland, 1967 .
The yabby is an r-selected species and, consequently, has the potential to reach sexual maturity at an early age and size, and produce large numbers of offspring by
Ž .
repeated spawning each season Stearns, 1976; Faragher, 1983; Lake and Sokol, 1986 . If population growth is uncontrolled by mortality due to periodic drought, yabbies can rapidly reach population densities where individual growth rates are greatly reduced.
One way to control population density is to prevent reproduction. Juvenile yabbies
Ž .
are produced during the warmer months of the year September–May by broodstock contained within farm dams where there is currently little or no control by harvestors over yabby reproduction or density. However, if farm dams were to be stocked with single sex individuals then reproduction could not occur and densities could not increase.
Controlling reproductive effort and density by stocking ponds with individuals of only one sex has been shown to be an effective way of increasing production in other freshwater crustaceans. For example, monosex culture of the freshwater prawn,
Macro-brachium rosenbergii, has demonstrated increased average weights for male populations
Ž
relative to mixed-sex or female-only populations Sagi et al., 1986; Cohen et al., 1988;
. Ž .
Hulata et al., 1988 . Monosex culture of redclaw Cherax quadricarinatus , a tropical freshwater crayfish, has demonstrated improved growth rates for male-only populations Ž1.12 grweek over mixed-sex populations 0.52 g. Ž rweek and female-only populations. Ž0.27 grweek. ŽCurtis and Jones, 1995 . Some reproduction occurred in ponds in their. experiment and the superior growth rate of all-male populations compared to all-female and mixed-sex cultivation was attributed to changes in density as well as retardation of female somatic growth due to the onset of sexual maturity. A more recent experiment evaluating the monosex growout of redclaw crayfish also demonstrated improved
Ž . Ž
growth for male-only populations 2.93 grweek over mixed-sex populations 1.31
. Ž . Ž .
grweek and female-only populations 1.06 grweek Sagi et al., 1997 . The improved growth rate for redclaw in this experiment, compared with that reported by Curtis and
Ž .
Jones 1995 , may be attributed to the use of weight frequency histograms by Sagi et al., Ž1997 to distinguish between stocked and newly recruited individuals..
2. Materials and methods
The Avondale Research Station is located in the Western Australian wheatbelt near
Ž X X
.
Beverley 3287 S, 116855 E . There were 25 clay ponds at the research station. Each pond was 1.5 m deep with a 10=10 m water surface area, 3:1 batter and a level floor. Ponds were individually fenced to prevent movement of yabbies between treatments. All 25 ponds received water from the same supply dam. The ponds were filled prior to stocking and thereafter topped up to replace water lost due to evaporation.
Eighteen of these 0.01-ha ponds were stocked with yabbies obtained from local harvestors at an initial density of 1rm2. Prior to stocking, the 1800 yabbies in this
experiment were sexed by manual examination for the presence of penes at the base of the fifth pair of periopods for males, or gonopores at the base of the third pair of periopods for females. Intersex animals were excluded from the study.
A completely randomized block design with two factors, sex and diet, was used.
Ž .
Factor sex had three levels, male, female and mixed-sex 1:1 ratio . Factor diet also had
Ž . y2 y1 Ž . y2
three levels, Lupin Lupinus albus 2.5 g m week , Lupin L. albus 5.0 g m
y1 Ž . y2 y1 Ž
week and WA Crayfish Reference Diet CRD 2.5 g m week Morrissy, 1990, .
1992; Lawrence et al., 1998 . There were two blocks: the first block consisted of northern ponds and the second block consisted of southern ponds.
A random sample of yabbies was weighed prior to stocking each treatment. The mean
Ž . Ž .
stocking weight "S.E. of yabbies in this experiment was 19.2"0.3 g ns180 .
Ž .
There was no significant difference Ps0.08 in the average initial weight for male Ž19.3"0.2 g. Žns90 and female 19.1. Ž "0.4 g. Žns 90 yabbies by a two-tailed.
t-test.
The ponds were stocked in July 1995 and harvested after 175 days so as to include five months of the yabby breeding season. All yabbies were removed by first trapping then draining the ponds to collect the remaining animals. Immediately after harvesting all yabbies were individually sexed and weighed.
Gross valuerha was calculated according to current industry values for standard size Ž
categories assuming that juveniles less than 30 g have no commercial value Lawrence, .
1998 .
3. Results
3.1. Water quality
Ž .
The water quality of the research ponds Table 1 was typical of farm dams in the
Ž .
Western Australian wheatbelt Lawrence et al., 1998 .
3.2. Size-frequency distribution
Ž Construction of weight-frequency histograms showed cohorts of juveniles arising
.
Table 1
Water quality of the research ponds at Avondale Research Station during the experiment
Parameter Units Mean
populations than the monosex populations. This was due to reproduction especially in
Ž .
the mixed-sex ponds Table 2 . The decreased number of juveniles, and therefore lower density, in monosex ponds favoured growth in these treatments. The mean weight of juveniles in mixed-sex ponds was 0.96"0.09 g, 1.00"0.77 g in male monosex ponds
Table 2
Ž .
Summary of results mean"S.E. for monosex and mixed-sex populations of C. albidus
Ž .
Mixed-sex 1:1 Male monosex Female monosex
Žns6 ponds. Žns6 ponds. Žns6 ponds.
Final juvenile g 0.96"0.09 1.00"0.77 2.44"0.29
Ž . Ž .
Growth adults Weight gain g 26.9 41.3 24.5
Ž .
Growth raterweek g 1.08 1.65 0.98
2
Final adultqjuvenile no.rm 10.38 1.31 6.19
Ž .
Biomass Adult g 3095"256 4161"269 3300"471
Ž .
Juvenile g 930"229 97"95 1193"256
Ž .
Total g 4025"323 4258"272 4493"508
Ž .
Ž .
and 2.44"0.29 g in female monosex ponds Table 2 . Juveniles could therefore be distinguished from adults during the analyses of data.
All male yabby ponds gave a greater proportion of larger adult animals, and therefore more valuable size classes at harvest, than all-female and mixed-sex ponds. The size frequency distribution of adult yabbies in female monosex, male monosex and mixed-sex treatments is shown in Fig. 1.
( )
3.3. Growth and surÕiÕal of adults excluding juÕeniles
Ž .
Analysis of variance revealed that neither the block effect Ps0.17 nor the
Ž .
interaction between sex and diet Ps0.70 had a significant effect on yabby growth.
Ž . Ž .
Both diet Ps0.049 and sex Ps0.001 had a significant effect upon yabby growth. For each diet treatment, the mean weight of yabby populations that contained only
Ž .
males was greater than mixed or female populations Fig. 2 . Furthermore, growth of yabbies was higher on the WA CRD in comparison to the standard industry practice of
Ž y2 y1. Ž . Ž y2
feeding lupins 2.5 g m week Fig. 2 . It required twice as much lupins 5 g m
Fig. 1. The weight-frequency distribution of female monosex, male monosex and mixed-sex yabby population
Fig. 2. The mean increase in weight of mixed-sex and monosex yabby populations fed three different diets.
y1. Ž y2 y1.
week to obtain similar growth to that achieved with WA CRD 2.5 g m week ŽFig. 2 . Consequently, monosex male populations fed WA CRD at 2.5 g m. y2 weeky1
produced yabbies that grew, on average, 88% faster than those grown under the standard
Ž y2 y1.
industry practice of feeding mixed-sex populations with lupins 2.5 g m week ŽFig. 2 ..
If ponds with the same sex treatment are grouped together, and juveniles excluded,
Ž . Ž . Ž
the final mean weight "S.E. of yabbies in male-only ponds 60.6"0.6 g ns6
. Ž . Ž
ponds was greater than that of female yabbies in monosex ponds 43.6"0.3 g ns6
. Ž . Ž . Ž .
ponds P-0.001 and mixed-sex yabby populations 46.1"0.6 g ns6 ponds ŽP-0.0001. ŽTable 2 . The male-only yabby ponds had a 52.8% higher growth rate. Ž1.65 grweek than mixed-sex populations 1.08 g. Ž rweek and 68.4% greater than.
Ž . Ž .
female-only ponds 0.98 grweek Table 2 . Female yabbies in monosex culture grew
Ž .
slower than mixed-sex populations Table 2 , but the difference was not statistically
Ž .
significant Ps0.31 .
Males in monosex culture grew 17% faster than the males in mixed-sex populations, while females in monosex culture grew 31% faster than the females in mixed-sex
Ž . Ž .
populations P-0.05 Table 3 .
Table 3
Ž .
Growth and survival means"S.E. of yabby males and females in mixed-sex and monosex populations
Žjuveniles excluded.
Males in Males in Females in Females in
mixed-sex monosex mixed-sex monosex
Ž .
Weight Initial g 19.2"0.3 19.3"0.2 19.2"0.3 19.1"0.4
Ž .
Final g 54.4"0.6 60.6"0.6 37.9"0.6 43.6"0.3
Ž .
Growth Weight gain g 35.2 41.3 18.7 24.5
Ž .
Growth rate grweek 1.41 1.65 0.75 0.98
Ž .
A generalized linear model with logit link was used to examine the survival of
Ž .
yabbies McCullagh and Nedler 1986 . The survival rate of yabbies in male monosex
Ž . Ž .
ponds was 7% higher Ps0.005 than in female monosex ponds Table 3 . There was no significant difference in the survival of males in monosex culture and mixed-sex
Ž . Ž .
culture Ps0.86 Table 3 . Similarly, females in monosex and mixed-sex culture had
Ž . Ž .
the same survival Ps0.64 Table 3 .
3.4. Economic significance of monosex culture
At current market prices, the ponds stocked with only male yabbies resulted in a 70%
Ž .
greater gross value of animals produced than from the mixed-sex ponds P-0.01 ŽTable 2 . However, there was no significant difference in the gross values of yabbies.
Ž .
produced from female-only and mixed-sex ponds Ps0.90 .
4. Discussion
Yabbies in a male monosex population grow faster than yabbies in either a female Ž .
monosex population or in a mixed-sex 1:1 population. The results of this experiment
Ž .
are similar to those obtained for redclaw Curtis and Jones, 1995; Sagi et al., 1997 and Ž
M. rosenbergii Sagi et al., 1986; Cohen et al., 1988; Hulata et al., 1988; Siddiqui et al.,
. Ž .
1997 Table 4 . Furthermore, the results of this experiment also show that while growth can be improved by either increasing feed rates of lupins or using a formulated diet ŽCRD , male monosex populations still grow faster. Importantly, these results also show.
Ž y2 y1.
that it requires twice the feed rate of lupins 5 g m week to achieve similar growth
Ž . Ž y2 y1.
to yabbies on a formulated diet CRD 2.5 g m week .
While the increased growth rates from male monosex culture compared with mixed-sex populations obtained in this experiment are less than those observed in redclaw
Table 4
Average growth rate of male and female monosex populations compared with average growth rate of
Ž .
mixed-sex populations 100% for yabbies, redclaw and M. rosenbergii
Species Growth rate of Growth rate of Reference
male monosex female monosex
Yabby C. albidus 153% 91% This study
b
Ž . Ž .
Redclaw C. quadricarinatus 215% 52% Curtis and Jones 1995
a
Ž . Ž .
Redclaw C. quadricarinatus 224% 81% Sagi et al. 1997
a
Ž .
M. rosenbergii 105% 95% Sagi et al. 1986
a
Ž .
M. rosenbergii 125% 78% Cohen et al. 1988
a
Ž .
M. rosenbergii 116% 85% Hulata et al. 1988
a
Ž .
M. rosenbergii 123% 69% Siddiqui et al. 1997
a
No juveniles or juveniles excluded. b
ŽCurtis and Jones, 1995; Sagi et al., 1997 , they are greater than those reported for M.. Ž
rosenbergii Sagi et al., 1986; Cohen et al., 1988; Hulata et al., 1988; Siddiqui et al.,
. Ž .
1997 Table 4 . The increased growth rates from female monosex populations com-pared with mixed-sex populations obtained in this experiment are greater than those
Ž .
reported for redclaw Curtis and Jones, 1995; Sagi et al., 1997 , or M. rosenbergii ŽCohen et al., 1988; Hulata et al., 1988; Siddiqui et al., 1997. ŽTable 4 ..
Ž .
In common with the results of Sagi et al. 1986 for M. rosenbergii, the increased growth of yabbies in male-only populations compared with female-only populations may
Ž .
be largely attributable to sexual dimorphism. Woodland 1967 reported that male yabbies grow at the same rate as females until sexual maturity, after which female growth slows down relative to that of males.
This experiment has also shown that both males and females in monosex culture grow significantly faster than males or females in mixed-sex culture. Males in monosex culture grew 17% faster than males in mixed-sex populations. Similarly, females in monosex culture grew 31% faster than those in mixed-sex populations. The improved growth of both male and female monosex populations relative to each sex in mixed-sex populations may also be due to the diversion of energy in mixed-sex populations from somatic growth to reproductive effort, i.e., competition for mates and production of
Ž .
gametes, as has been reported for redclaw Curtis and Jones, 1995 .
As price for yabbies increases with increasing size, the increased mean weights obtained from monosex culture are of considerable significance to the yabby aquaculture industry. This experiment has shown that, based upon current prices, stocking ponds with only male yabbies resulted in a 70% greater gross value of animals produced than the mixed-sex production.
However, while manual sexing of yabbies to stock monosex populations in wheatbelt farm dams and semi-intensive ponds is becoming more common in Australia, it is labour intensive. Recent experiments, involving crosses of strains of yabbies from around
Ž
Australia, have resulted in an all-male hybrid Lawrence et al., 1998; Lawrence, .
unpublished data and this new technique will greatly facilitate the commercial monosex culture of male yabbies.
Acknowledgements
This work was supported by funding from FRDC Project No. 94r75. We thank M. Stuckey, technical officer, Fisheries WA, for assistance in maintaining the experiments and Neil Sumner for assistance with data analyses. We also thank Dr. Greg Maguire, Dr. Nick Caputi and Norm Hall for their comments.
References
Cohen, D., Sagi, A., Ra’anan, Z., Zohar, G., 1988. The production of Macrobrachium rosenbergii in monosex populations: III. yield characteristics under intensive monoculture conditions in earthen ponds. Bamidgeh 40, 57–63.
Curtis, M.C., Jones, C.M., 1995. Observations on monosex culture of redclaw crayfish Cherax
quadricarina-Ž .
tus von Martens Decapoda:Parastacidae in earthen ponds. J. World Aquacult. Soc. 26, 154–159. Faragher, R.A., 1983. Role of the crayfish Cherax destructor Clark as food for trout in Lake Eucumbene, New
South Wales. Aust. J. Mar. Freshwater Res. 33, 407–417.
Hulata, G., Karplus, I., Wohlfarth, G.W., Halevy, A., Cohen, D., Sagi, A., Ra’anan, Z., 1988. The production of Macrobrachium rosenbergii in monosex populations: II. Yield characteristics in polyculture ponds. Isr. J. Aquacult.-Bamidgeh 40, 9–16.
Ž
Lake, P.S., Sokol, A., 1986. Ecology of the yabby Cherax destructor Clark
Crustacea:Decapoda:Parastaci-.
dae and its potential as a sentinel animal for mercury and lead pollution. Australian Water Resources Council, Canberra. Technical Paper No. 87, 186 pp.
Ž .
Lawrence, C.S., 1998. Yabbies. In: Hyde, K.W. Ed. , The New Rural Industries — A Handbook for Farmers and Investors. Rural Industries Research and Development, Canberra, pp. 147–152.
Lawrence, C.S., Morrissy, N.M. Bellanger, J.E., Cheng, Y.W., 1998. Final report FRDC Project 94r075 : Enhancement of yabby production from Western Australian farm dams. Fisheries Research Report No. 112, Fisheries Western Australia, 134 pp.
McCullagh, P., Nedler, J.A., 1986. Generalized Linear Models. 2nd edn. Chapman & Hall, London. Morrissy, N.M., 1990. Report on the development of a WA crayfish reference pond diet. Marron Growers
Bulletin 12, 9–13, April.
Morrissy, N.M., 1992. Feed development for marron, Cherax tenuimanus, in Western Australia. In: Allan, G.,
Ž .
Dall, W. Eds. , Proc. Aquaculture Nutrition Workshop, Salamander Bay, 15–17 April 1991. NSW Fisheries, Brackish Water Fish Culture Research Station, Salamander Bay, Australia, pp. 72–76. Sagi, A., Milstein, A., Eran, Y., Joseph, D., Khalaila, I., Abdu, U., Harpaz, S., Karplus, I., 1997. Culture of
Ž .
the Australian red-claw crayfish Cherax quadricarinatus in Israel: II. Second growout season of overwintered populations. Isr. J. Aquacult.-Bamidgeh 49, 222–229.
Sagi, A., Ra’anan, Z., Cohen, D., Wax, Y., 1986. Production of Macrobrachium rosenbergii in monosex populations: yield characteristics under intensive monoculture conditions in cages. Aquaculture 51, 265–275.
Siddiqui, A.Q., Al-Hafedh, Y.S., Al-Harbi, A.H., Ali, S.A., 1997. Effects of stocking density and monosex culture of freshwater prawn Macrobrachium rosenbergii on growth and production in concrete tanks in Saudi Arabia. J. World Aquacult. Soc. 28, 106–112.
