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Egg development time and storage for redclaw crayfish Cherax quadricarinatus von Martens
275
Aquaculture, 109 (1993)275-280 Elsevier Science Publishers B.V., Amsterdam AQUA 40038
Egg development time and storage for redclaw crayfish Cherax quadricarinatus von Martens Chris R. King School of Life Science, Queensland Universityof Technology. Brisbane, Qld.. Australia (Accepted I 8 August 1992 )
ABSTRACT King, C.R., 1993. Egg development time and storage for redclaw crayfish Cherax quadricarinatus von Martens. Aquaculture, 109: 275-280. Eggs stripped from redclaw crayfish, Cherax quadricarinatus, were incubated at constant temperatures within the range lo-37°C. Hatching only occurred between 22 and 32°C and full development took 30 days less at 32°C. Surface treatment of eggs, using chlorine or a mixture of malachite green and methylene blue, was necessary to prevent microbial destruction of eggs. Attempts to store eggs at low temperatures, 5 and 10°C were unsuccessful.
INTRODUCTION
Egg development time is highly dependent on temperature in crustaceans (Bottrell, 1975; Herzig, 1983). Eggs of decapods develop faster at higher temperatures (Mason, 1977; Aiken and Waddy, 1985; Westin and Gydemo, 1986; Hessen et al., 1987; Sammy, 1988 ). This characteristic offers greater management flexibility in aquaculture. Egg development could be regulated so that eggs produced at different times hatch synchronously (Mason 1977; Aiken and Waddy, 1985; Westin and Gydemo, 1986; Hessen et al., 1987). Stripped eggs have been hatched successfully for several species of crayfish (Morrissy, 1976; Mason, 1977; Waugh, 1980; Hessen et al., 1987) including redclaw (Herbert, 1987a). On a large scale this could save space in hatcheries, and increase convenience by not having to provide specialised chambers, and care, for berried females. Some temperate species carry their eggs over winter (Abrahamsson and Goldman, 1970; Aiken and Waddy, 1985; Brewis and Bowler, 1985; Hessen et al., 1987; Nelson et al., 1988) indicating a delayed development. If stripped eggs could be stored at low temperature, then Correspondence to: Dr. C.R. King, School of Life Science, Queensland ogy, P.O. Box 2434, Brisbane, Qld. 400 1, Australia.
0044-8486/93/$06.00
0 1993 Elsevier Science Publishers
University
B.V. All rights reserved.
of Technol-
276
C.R. KlNG
not only could hatching be regulated, but eggs could also be transported rather than later stages. The risk of inadvertently spreading disease organisms might then be reduced. The major objectives of this study were to determine the relationship between egg development time and temperature for redclaw crayfish, and to examine the feasibility of storing and hatching stripped eggs. MATERIALS AND METHODS
Pilot trials revealed that it took up to 3 days from extrusion for egg membranes to harden. The eggs disintegrated if removed earlier, as found by others (Sammy, 1988; Jones, 1990). Consequently, eggs were stripped from females 4 days after spawning. Pilot trials also confirmed that stripped eggs did not survive unless microbial growth was controlled (Morrissy, 1976; Herbert, 1987a). It was therefore necessary to find a treatment that could suppress microbial growth before the effect of temperature on egg development could be determined. Several treatments were compared for their ability to suppress microbial attack. Eggs were suspended for 5 min every 2 days in a mixture of malachite green and methylene blue, either 5 or 10 mg l- I, treatments M-5 and M- 10 respectively, or in chlorine solutions containing 25,38, 100 and 200 mg l- ’ of available chlorine (C-25...C-200). Additionally, eggs were suspended for 30 min every 2 days in solution M-5 (M-5-30). One hundred eggs were used for each treatment. These were divided into batches of 10, each batch being held in 30 ml of pre-aerated water in sealed plastic containers. Each day the eggs were checked, the water gently agitated and mouldy (or otherwise damaged) eggs removed. Incubation was at 25°C. The water and containers were renewed each week. One of the successful treatments, M-5, was then used for the temperaturedevelopment time trials. The temperatures used were: 10, 15, 18,20,22,22.8, 24.5, 25,26, 27.2, 28, 29.5, 32, 34.3, and 37.2”C. At each temperature, 60100 eggs were incubated following the above procedure. Egg storage was tested by retaining eggs at 5 and 10’ C as above but under sterile conditions. Each week, after 4 weeks of storage (considered to be the minimum useful storage time), one vial of 10 eggs was transferred to 25 “C (gradual increase over 1 day) incubated as above, and examined for development every 2 days. RESULTS
Development was typical of Parastacidae (Hopkins, 1967; Felder et al., 1985; Jones, 1990). Initially the extruded egg was uniformly opaque and orange. The sequence of development was then as follows: a clear patch contain-
271
EGG DEVELOPMENTTIME AND STORAGE FOR REDCLAW CRAYFISH
ing faintly visible somites formed, the heartbeat began, the yolk became indented, appendages and then the eyespots became visible, and the young crayfish eventually filled the egg, enclosing the remaining yolk within the cephalothorax. At this stage the crayfish hatched and the hatchling crayfish had a globular yolk-filled cephalothorax, and eyes that were not stalked. After the first moult the cephalothorax was less globular, the yolk reduced, and the eyes were stalked. After the second moult the crayfish were externally similar to adults. None of the surface treatments was entirely successful in preventing egg losses. Greatest survival occurred with treatments M-5, M- 10 and C-25 (59, 48 and 63%, respectively). Survival between these treatments did not differ significantly (,$ = 0.77, d.f. = 2, P= 0.68 ). Treatment M-5-30, with survival of 34%, was less effective (y= 17.8, d.f. = 3, P=O.O005). All other treatments were either ineffective against microbial attack or caused the eggs to fragment. No eggs hatched at temperatures above 32 ‘C or below 22 ‘C. At the higher temperatures eggs fragmented within 2 weeks and showed no development. In contrast, at the lower temperatures, eggs did not disintegrate (even when mouldy). Additionally, the first developmental stage (clear patch) was reached at 15 ‘C, and the eyespot stage at 18 and 20’ C. Within the temperature range 22-32 ‘C development times decreased curvilinearly (Fig. 1) with temperature ( T” C ). The period (days) from extru-
80
I
I
I
I
v moult 2 0 moult 1
V
70
0 hatching zi 2
80
Q
50
E ;
40
Exl * 30 A 20 10 18
I
I
I
1
I
21
24
27
30
33
Temperature
-1
38
(‘c)
Fig. 1. The relationships between temperature and development and to the first and second moults, for redclaw crayfish.
time, from egg extrusion to hatching
278
CR. KING
sion to hatching (H), to the first moult (M 1) and to the second moult (M2 ) being described by the following equations: In (H ) = 10.62 - 2.21n ( T) (F,,,=56.2, P=O.OOl, ?=0.89); l/Ml=O.O024T-0.034 (F,,3=473, P
Colour changes have been noted during the development of some species’ eggs, from brown to dark red in Puranephrops plunifrons (Hopkins, 1967), and from brown to orange for Austropotamobius pallipes (Woodlock and Reynolds, 1988). Jones ( 1990) used the colour changes in developing redclaw eggs, green to orange and then dark red, to help distinguish stages. This sequence of colour changes was also noted by Herbert ( 1987b) for redclaw from the same location (Mitchell River, Queensland), although he also found that the sequence could be orange to green to red, or as found in the present study, eggs could remain orange throughout development. Redclaw eggs from the Jardine River, which are dark green, almost black (Herbert, 1987b), and from the Finnis River region (near Darwin) which are khaki (Sammy, 1988 ) also do not change colour during development. Egg colouration, and colour constancy during development, may therefore be variable characteristics that could reflect strain differences. Juvenile redclaw crayfish could not survive temperatures of 32-34°C (Jones, 1990). This matches the upper critical temperature for eggs found in the present study. Nevertheless, eggs appear to have a more narrow temperature tolerance range than juveniles because eggs did not develop below 22’ C, whereas Jones ( 1990) found that juveniles survived well at 20 ‘C. These lower critical temperatures correspond to the range 2 l-22 ‘C, where breeding activity in natural populations of redclaw begins (Sammy, 1988; Jones, 1990). Although some development occurred at 18 and 20 “C, eggs failed to develop beyond the eyespot stage. Appleberg ( 1983) found that oxygen uptake in crayfish eggs increased about twenty-fold from extrusion to pre-hatching, increasing to thirty-fold at hatching. It is possible that such large increases in metabolic activity could not be accomplished at the lower temperatures, thus preventing full development of redclaw eggs. Eggs of temperate species can tolerate extended periods of low temperature (Abrahamsson and Goldman, 1970; Aiken and Waddy, 1985; Brewis and Bowler, 1985; Hessen et al., 1987; Nelson et al., 1988 ) and may require periods of cold to develop properly (Mason, 1977; Hessen et al., 1987). In con-
EGG DEVELOPMENT TIME AND STORAGE FOR REDCLAW CRAYFISH
219
trast, redclaw eggs could not be revived after 1 month of exposure to 10’ C (or lower) and storage at such low temperatures may not be feasible. Nevertheless, limited storage of partially developed eggs, at temperatures between 18 and 20’ C, might be possible. Sammy (1988) found that the period between egg extrusion and juvenile release in redclaw crayfish was about 2 months at 2 l-22 “C, similar to the estimate of 66 days from this study. However, at 26-29 ‘C, Sammy’s crayfish achieved release in 1 month compared with 42-50 days (this study), and 72 days recorded by Jones ( 1990). Additionally, Jones’ ( 1990) redclaw eggs took 50 days to hatch (at 25-26 “C) compared with 32-34 days in this study. These differences suggest that the relationship between temperature and egg development may vary between different local populations of redclaw crayfish. Sammy’s crayfish were from the Northern Territory, the others came from north Queensland. Strains that develop quickly would be ideal for hatchery production. By keeping eggs at 32°C rather than 22”C, hatching and juvenile release can be decreased by about 30 days. Furthermore, synchronous hatching could be achieved for eggs produced up to 30 days apart by appropriately adjusting their incubation temperatures. This could be important for a highly regulated hatchery production process, but the latter is not necessarily worthwhile (Morrissy, 1976; Jones, 1990). Eggs of As&us astacus have been hatched without suffering from microbial attack or substantial losses (Hessen et al., 1987). However, microbial attack, and egg losses for redclaw, increase when dissolved oxygen concentration falls below saturation and when pH falls below 6.0 (Sammy 1988 ) . Herbert ( 1987a) used malachite green (0.1 mg l- ’ ) to control microbial growth on redclaw eggs, Morrissy ( 1976) used penicillin for eggs of Cherax tenuimanus, whilst for other species neomycin (Fisher et al., 1978) and Wescodyne ( Aiken and Waddy, 1985 ) have been used. Chlorine (25 mg l- ’ ) and malachite green/methylene blue treatments afforded partial protection for redclaw eggs in this study. Preliminary trials (unpublished) using large batches of eggs ( lOOO-2000), suspended in flowing water, with the M-5, or C-25 treatments being applied even daily, have failed to produce hatchlings even though dissolved oxygen and pH were within Sammy’s ( 1988) recommended ranges. Effective control of microbial growth, crucial for hatching stripped eggs, may prove to be too difficult or too expensive for large-scale operations for redclaw crayfish. ACKNOWLEDGEMENTS
This research was supported by finance from CSR Ltd. and QUT. I would like to thank J. Erbacher, D. Owens, R. Whyte and Wu Xingyong (of Nanjing University) for their assistance at various times throughout this program.
280
CR. KING
REFERENCES Abrahamsson, S.A.A. and Goldman, CR., 1970. Distribution, density and production of the crayfish Pucifastacus leniusculus Dana in Lake Tahoe, California-Nevada. Oikos. 2 1: 8391. Aiken, D.E. and Waddy, S.L., 1985. Production of seedstock for lobster culture. Aquaculture, 44: 103-l 14. Appleberg, M.A.P., 1983. Response of acid stress upon the oxygen uptake in eggs ofthe crayfish Astacus astacus L. In: C.R. Goldman (Editor), Freshwater Crayfish V. Proceedings of the Fifth International Symposium on Freshwater Crayfish. Davis, CA, Avi Publishing Company, pp. 59-69. Bottrell, H.H., 1975. Generation time, length of life, instar duration and frequency of moulting, and their relationship to temperature in eight species of Cladocera from the river Thames, Reading. Oecologia (Berlin ), 19: 129- 140. Brewis, J.M. and Bowler, K., 1985. A study of reproductive females of the freshwater crayfish Ausfropotamobius pallipes. Hydrobiologia, 12 1: 145- 149. Felder, D.L., Martin, J.W. and Goy, J.W., 1985. Patterns in early postlarval development of decapods. In: A.M. Wenner (Editor), Crustacean Issues 2, Larval Growth. A.A. Balkema, Rotterdam, Netherlands, pp. 163-225. Fisher, W.S., Nilson, E.H., Steenberg, J.F. and Lightner, D.V.. 1978. Microbial diseases of cultured lobsters: a review. Aquaculture, 14: 115- 140. Herbert, B., 1987a. Notes on diseases and epibionts of Cherux quadricarinatus and C. tenuimanus (Decapoda: Parastacidae). Aquaculture, 64: 165-173. Herbert, B., 1987b. Note on Cherax quadricarinatus from the Jardine river, Cape York Peninsula. Qld. Nat., 28: 19-2 1. Herzig, A., 1983. The ecological significance of the relationship between temperature and duration of the embryonic development in planktonic freshwater copepods. Hydrobiologia, 100: 65-91. Hessen, D., Taugbol, T., Field, E. and Skurdal, J., 1987. Egg development and life cycle timing in the noble crayfish (Astacus astacus). Aquaculture, 64: 77-82. Hopkins, CL., 1967. Breeding in the freshwater crayfish Purunephropsplanifrons White. N.Z. J. Mar. Freshwater Res., 1: 51-58. Jones, C., 1990. The biology and aquaculture potential of the tropical freshwater crayfish Cherux quadricarinatus. Qld. Dept. Primary Ind. Inf. Ser., QI90028, 109 pp. Mason, M.C., 1977. Artificial incubation of crayfish eggs (Pucifastacus leniusculus (Dana) ). In: O.V. Lindqvist (Editor), Freshwater Crayfish, III, Kuopio, Finland, 1976, pp. 119-l 32. Morrissy, N.M., 1976. Aquaculture of marron, Cherux tenuimanus (Smith). Part 2. Breeding and early rearing. Fish. Res. Bull. West. Aust., 17: l-32. Nelson, K., Hedgecock, D. and Borgenson, W., 1988. Factors influencing egg extrusion in the American lobster (Homarus americanus). Can. J. Fish. Aquat. Sci., 45: 797-804. Sammy, N., 1988. Breeding biology of Cherux quadricarinatus in the Northern Territory. In: Proceedings of the First Australian Shellfish Aquaculture Conference, Perth, Curtin University Press, pp. 79-88. Waugh, D.G., 1980. Koura culture Parunephrops plunifrons. N.Z. Fish. Res. Leafl., 10. Westin, I. and Gydemo, R., 1986. Influence of light and temperature on reproduction and moulting frequency of the crayfish, Astacus astacus L. Aquaculture, 52: 43-50. Woodlock, B. and Reynolds, J.D., 1988. Laboratory breeding studies of freshwater crayfish. Austropotamobiuspallipes (Lereboullet). Freshwater Biol., 19: 71-78.
Aquaculture, 109 (1993)275-280 Elsevier Science Publishers B.V., Amsterdam AQUA 40038
Egg development time and storage for redclaw crayfish Cherax quadricarinatus von Martens Chris R. King School of Life Science, Queensland Universityof Technology. Brisbane, Qld.. Australia (Accepted I 8 August 1992 )
ABSTRACT King, C.R., 1993. Egg development time and storage for redclaw crayfish Cherax quadricarinatus von Martens. Aquaculture, 109: 275-280. Eggs stripped from redclaw crayfish, Cherax quadricarinatus, were incubated at constant temperatures within the range lo-37°C. Hatching only occurred between 22 and 32°C and full development took 30 days less at 32°C. Surface treatment of eggs, using chlorine or a mixture of malachite green and methylene blue, was necessary to prevent microbial destruction of eggs. Attempts to store eggs at low temperatures, 5 and 10°C were unsuccessful.
INTRODUCTION
Egg development time is highly dependent on temperature in crustaceans (Bottrell, 1975; Herzig, 1983). Eggs of decapods develop faster at higher temperatures (Mason, 1977; Aiken and Waddy, 1985; Westin and Gydemo, 1986; Hessen et al., 1987; Sammy, 1988 ). This characteristic offers greater management flexibility in aquaculture. Egg development could be regulated so that eggs produced at different times hatch synchronously (Mason 1977; Aiken and Waddy, 1985; Westin and Gydemo, 1986; Hessen et al., 1987). Stripped eggs have been hatched successfully for several species of crayfish (Morrissy, 1976; Mason, 1977; Waugh, 1980; Hessen et al., 1987) including redclaw (Herbert, 1987a). On a large scale this could save space in hatcheries, and increase convenience by not having to provide specialised chambers, and care, for berried females. Some temperate species carry their eggs over winter (Abrahamsson and Goldman, 1970; Aiken and Waddy, 1985; Brewis and Bowler, 1985; Hessen et al., 1987; Nelson et al., 1988) indicating a delayed development. If stripped eggs could be stored at low temperature, then Correspondence to: Dr. C.R. King, School of Life Science, Queensland ogy, P.O. Box 2434, Brisbane, Qld. 400 1, Australia.
0044-8486/93/$06.00
0 1993 Elsevier Science Publishers
University
B.V. All rights reserved.
of Technol-
276
C.R. KlNG
not only could hatching be regulated, but eggs could also be transported rather than later stages. The risk of inadvertently spreading disease organisms might then be reduced. The major objectives of this study were to determine the relationship between egg development time and temperature for redclaw crayfish, and to examine the feasibility of storing and hatching stripped eggs. MATERIALS AND METHODS
Pilot trials revealed that it took up to 3 days from extrusion for egg membranes to harden. The eggs disintegrated if removed earlier, as found by others (Sammy, 1988; Jones, 1990). Consequently, eggs were stripped from females 4 days after spawning. Pilot trials also confirmed that stripped eggs did not survive unless microbial growth was controlled (Morrissy, 1976; Herbert, 1987a). It was therefore necessary to find a treatment that could suppress microbial growth before the effect of temperature on egg development could be determined. Several treatments were compared for their ability to suppress microbial attack. Eggs were suspended for 5 min every 2 days in a mixture of malachite green and methylene blue, either 5 or 10 mg l- I, treatments M-5 and M- 10 respectively, or in chlorine solutions containing 25,38, 100 and 200 mg l- ’ of available chlorine (C-25...C-200). Additionally, eggs were suspended for 30 min every 2 days in solution M-5 (M-5-30). One hundred eggs were used for each treatment. These were divided into batches of 10, each batch being held in 30 ml of pre-aerated water in sealed plastic containers. Each day the eggs were checked, the water gently agitated and mouldy (or otherwise damaged) eggs removed. Incubation was at 25°C. The water and containers were renewed each week. One of the successful treatments, M-5, was then used for the temperaturedevelopment time trials. The temperatures used were: 10, 15, 18,20,22,22.8, 24.5, 25,26, 27.2, 28, 29.5, 32, 34.3, and 37.2”C. At each temperature, 60100 eggs were incubated following the above procedure. Egg storage was tested by retaining eggs at 5 and 10’ C as above but under sterile conditions. Each week, after 4 weeks of storage (considered to be the minimum useful storage time), one vial of 10 eggs was transferred to 25 “C (gradual increase over 1 day) incubated as above, and examined for development every 2 days. RESULTS
Development was typical of Parastacidae (Hopkins, 1967; Felder et al., 1985; Jones, 1990). Initially the extruded egg was uniformly opaque and orange. The sequence of development was then as follows: a clear patch contain-
271
EGG DEVELOPMENTTIME AND STORAGE FOR REDCLAW CRAYFISH
ing faintly visible somites formed, the heartbeat began, the yolk became indented, appendages and then the eyespots became visible, and the young crayfish eventually filled the egg, enclosing the remaining yolk within the cephalothorax. At this stage the crayfish hatched and the hatchling crayfish had a globular yolk-filled cephalothorax, and eyes that were not stalked. After the first moult the cephalothorax was less globular, the yolk reduced, and the eyes were stalked. After the second moult the crayfish were externally similar to adults. None of the surface treatments was entirely successful in preventing egg losses. Greatest survival occurred with treatments M-5, M- 10 and C-25 (59, 48 and 63%, respectively). Survival between these treatments did not differ significantly (,$ = 0.77, d.f. = 2, P= 0.68 ). Treatment M-5-30, with survival of 34%, was less effective (y= 17.8, d.f. = 3, P=O.O005). All other treatments were either ineffective against microbial attack or caused the eggs to fragment. No eggs hatched at temperatures above 32 ‘C or below 22 ‘C. At the higher temperatures eggs fragmented within 2 weeks and showed no development. In contrast, at the lower temperatures, eggs did not disintegrate (even when mouldy). Additionally, the first developmental stage (clear patch) was reached at 15 ‘C, and the eyespot stage at 18 and 20’ C. Within the temperature range 22-32 ‘C development times decreased curvilinearly (Fig. 1) with temperature ( T” C ). The period (days) from extru-
80
I
I
I
I
v moult 2 0 moult 1
V
70
0 hatching zi 2
80
Q
50
E ;
40
Exl * 30 A 20 10 18
I
I
I
1
I
21
24
27
30
33
Temperature
-1
38
(‘c)
Fig. 1. The relationships between temperature and development and to the first and second moults, for redclaw crayfish.
time, from egg extrusion to hatching
278
CR. KING
sion to hatching (H), to the first moult (M 1) and to the second moult (M2 ) being described by the following equations: In (H ) = 10.62 - 2.21n ( T) (F,,,=56.2, P=O.OOl, ?=0.89); l/Ml=O.O024T-0.034 (F,,3=473, P
Colour changes have been noted during the development of some species’ eggs, from brown to dark red in Puranephrops plunifrons (Hopkins, 1967), and from brown to orange for Austropotamobius pallipes (Woodlock and Reynolds, 1988). Jones ( 1990) used the colour changes in developing redclaw eggs, green to orange and then dark red, to help distinguish stages. This sequence of colour changes was also noted by Herbert ( 1987b) for redclaw from the same location (Mitchell River, Queensland), although he also found that the sequence could be orange to green to red, or as found in the present study, eggs could remain orange throughout development. Redclaw eggs from the Jardine River, which are dark green, almost black (Herbert, 1987b), and from the Finnis River region (near Darwin) which are khaki (Sammy, 1988 ) also do not change colour during development. Egg colouration, and colour constancy during development, may therefore be variable characteristics that could reflect strain differences. Juvenile redclaw crayfish could not survive temperatures of 32-34°C (Jones, 1990). This matches the upper critical temperature for eggs found in the present study. Nevertheless, eggs appear to have a more narrow temperature tolerance range than juveniles because eggs did not develop below 22’ C, whereas Jones ( 1990) found that juveniles survived well at 20 ‘C. These lower critical temperatures correspond to the range 2 l-22 ‘C, where breeding activity in natural populations of redclaw begins (Sammy, 1988; Jones, 1990). Although some development occurred at 18 and 20 “C, eggs failed to develop beyond the eyespot stage. Appleberg ( 1983) found that oxygen uptake in crayfish eggs increased about twenty-fold from extrusion to pre-hatching, increasing to thirty-fold at hatching. It is possible that such large increases in metabolic activity could not be accomplished at the lower temperatures, thus preventing full development of redclaw eggs. Eggs of temperate species can tolerate extended periods of low temperature (Abrahamsson and Goldman, 1970; Aiken and Waddy, 1985; Brewis and Bowler, 1985; Hessen et al., 1987; Nelson et al., 1988 ) and may require periods of cold to develop properly (Mason, 1977; Hessen et al., 1987). In con-
EGG DEVELOPMENT TIME AND STORAGE FOR REDCLAW CRAYFISH
219
trast, redclaw eggs could not be revived after 1 month of exposure to 10’ C (or lower) and storage at such low temperatures may not be feasible. Nevertheless, limited storage of partially developed eggs, at temperatures between 18 and 20’ C, might be possible. Sammy (1988) found that the period between egg extrusion and juvenile release in redclaw crayfish was about 2 months at 2 l-22 “C, similar to the estimate of 66 days from this study. However, at 26-29 ‘C, Sammy’s crayfish achieved release in 1 month compared with 42-50 days (this study), and 72 days recorded by Jones ( 1990). Additionally, Jones’ ( 1990) redclaw eggs took 50 days to hatch (at 25-26 “C) compared with 32-34 days in this study. These differences suggest that the relationship between temperature and egg development may vary between different local populations of redclaw crayfish. Sammy’s crayfish were from the Northern Territory, the others came from north Queensland. Strains that develop quickly would be ideal for hatchery production. By keeping eggs at 32°C rather than 22”C, hatching and juvenile release can be decreased by about 30 days. Furthermore, synchronous hatching could be achieved for eggs produced up to 30 days apart by appropriately adjusting their incubation temperatures. This could be important for a highly regulated hatchery production process, but the latter is not necessarily worthwhile (Morrissy, 1976; Jones, 1990). Eggs of As&us astacus have been hatched without suffering from microbial attack or substantial losses (Hessen et al., 1987). However, microbial attack, and egg losses for redclaw, increase when dissolved oxygen concentration falls below saturation and when pH falls below 6.0 (Sammy 1988 ) . Herbert ( 1987a) used malachite green (0.1 mg l- ’ ) to control microbial growth on redclaw eggs, Morrissy ( 1976) used penicillin for eggs of Cherax tenuimanus, whilst for other species neomycin (Fisher et al., 1978) and Wescodyne ( Aiken and Waddy, 1985 ) have been used. Chlorine (25 mg l- ’ ) and malachite green/methylene blue treatments afforded partial protection for redclaw eggs in this study. Preliminary trials (unpublished) using large batches of eggs ( lOOO-2000), suspended in flowing water, with the M-5, or C-25 treatments being applied even daily, have failed to produce hatchlings even though dissolved oxygen and pH were within Sammy’s ( 1988) recommended ranges. Effective control of microbial growth, crucial for hatching stripped eggs, may prove to be too difficult or too expensive for large-scale operations for redclaw crayfish. ACKNOWLEDGEMENTS
This research was supported by finance from CSR Ltd. and QUT. I would like to thank J. Erbacher, D. Owens, R. Whyte and Wu Xingyong (of Nanjing University) for their assistance at various times throughout this program.
280
CR. KING
REFERENCES Abrahamsson, S.A.A. and Goldman, CR., 1970. Distribution, density and production of the crayfish Pucifastacus leniusculus Dana in Lake Tahoe, California-Nevada. Oikos. 2 1: 8391. Aiken, D.E. and Waddy, S.L., 1985. Production of seedstock for lobster culture. Aquaculture, 44: 103-l 14. Appleberg, M.A.P., 1983. Response of acid stress upon the oxygen uptake in eggs ofthe crayfish Astacus astacus L. In: C.R. Goldman (Editor), Freshwater Crayfish V. Proceedings of the Fifth International Symposium on Freshwater Crayfish. Davis, CA, Avi Publishing Company, pp. 59-69. Bottrell, H.H., 1975. Generation time, length of life, instar duration and frequency of moulting, and their relationship to temperature in eight species of Cladocera from the river Thames, Reading. Oecologia (Berlin ), 19: 129- 140. Brewis, J.M. and Bowler, K., 1985. A study of reproductive females of the freshwater crayfish Ausfropotamobius pallipes. Hydrobiologia, 12 1: 145- 149. Felder, D.L., Martin, J.W. and Goy, J.W., 1985. Patterns in early postlarval development of decapods. In: A.M. Wenner (Editor), Crustacean Issues 2, Larval Growth. A.A. Balkema, Rotterdam, Netherlands, pp. 163-225. Fisher, W.S., Nilson, E.H., Steenberg, J.F. and Lightner, D.V.. 1978. Microbial diseases of cultured lobsters: a review. Aquaculture, 14: 115- 140. Herbert, B., 1987a. Notes on diseases and epibionts of Cherux quadricarinatus and C. tenuimanus (Decapoda: Parastacidae). Aquaculture, 64: 165-173. Herbert, B., 1987b. Note on Cherax quadricarinatus from the Jardine river, Cape York Peninsula. Qld. Nat., 28: 19-2 1. Herzig, A., 1983. The ecological significance of the relationship between temperature and duration of the embryonic development in planktonic freshwater copepods. Hydrobiologia, 100: 65-91. Hessen, D., Taugbol, T., Field, E. and Skurdal, J., 1987. Egg development and life cycle timing in the noble crayfish (Astacus astacus). Aquaculture, 64: 77-82. Hopkins, CL., 1967. Breeding in the freshwater crayfish Purunephropsplanifrons White. N.Z. J. Mar. Freshwater Res., 1: 51-58. Jones, C., 1990. The biology and aquaculture potential of the tropical freshwater crayfish Cherux quadricarinatus. Qld. Dept. Primary Ind. Inf. Ser., QI90028, 109 pp. Mason, M.C., 1977. Artificial incubation of crayfish eggs (Pucifastacus leniusculus (Dana) ). In: O.V. Lindqvist (Editor), Freshwater Crayfish, III, Kuopio, Finland, 1976, pp. 119-l 32. Morrissy, N.M., 1976. Aquaculture of marron, Cherux tenuimanus (Smith). Part 2. Breeding and early rearing. Fish. Res. Bull. West. Aust., 17: l-32. Nelson, K., Hedgecock, D. and Borgenson, W., 1988. Factors influencing egg extrusion in the American lobster (Homarus americanus). Can. J. Fish. Aquat. Sci., 45: 797-804. Sammy, N., 1988. Breeding biology of Cherux quadricarinatus in the Northern Territory. In: Proceedings of the First Australian Shellfish Aquaculture Conference, Perth, Curtin University Press, pp. 79-88. Waugh, D.G., 1980. Koura culture Parunephrops plunifrons. N.Z. Fish. Res. Leafl., 10. Westin, I. and Gydemo, R., 1986. Influence of light and temperature on reproduction and moulting frequency of the crayfish, Astacus astacus L. Aquaculture, 52: 43-50. Woodlock, B. and Reynolds, J.D., 1988. Laboratory breeding studies of freshwater crayfish. Austropotamobiuspallipes (Lereboullet). Freshwater Biol., 19: 71-78.