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Cold tolerance at three salinities in post-larval prawns, Macrobrachium rosenbergii (De Man)
Aquaculture, 15 (1978) 249-255 o Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
249
COLD TOLERANCE AT THREE SALINITIES IN POST-LARVAL PRAWNS, MACROBRACHIUM ROSENBERGII (DE MAN)
S. UNGLAUB SILVERTHORN* Department
and ANNE M. REESE
of Physiology, Medical University of South Carolina, Charleston, S. C.
29402 (U.S.A.) *Present address: Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston, Texas 77550 (U.S.A.) This work was sponsored by N.O.A.A., under grant number 04-6-158-44096.
Office of Sea Grant, Department of Commerce,
(Received 22 April 1978; revised 2 August 1978)
ABSTRACT Silverthorn, S. U. and Reese, A.M., 1978. Cold tolerance at three salinities in post-larval prawns, Macrobrachium rosenbergii (De Man). Aquaculture, 15: 249-255. Post-larval Macrobrachium rosenbergii acclimated to 27, 22, or 16°C and 5, 8, or 14 “/,,, were temperature-shocked to 16°C or 13” /lS”C for 1 week. Survival was significantly better in animals acclimated to 22” C or below. Salinity had no significant effect on survival. Growth of post-larvae which had been maintained at 16°C or below for 3 weeks was followed for 1 month at 27” C; it was not significantly different from that of 27” C controls. Slower growth was observed in the 14’/,, prawns. These data indicate that postlarvae stocked into cool ponds from warm hatcheries might benefit from pre-acclimation to lower temperatures. Exposure to cold does not adversely affect later growth.
INTRODUCTION
The giant Malaysian prawn, Mucrobruchium rosenbergii, is currently under investigation as a candidate for aquaculture in many areas of the world, including the continental United States (Goodwin and Hanson, 1975; Ling and Costello, 1976; Sandifer and Smith, 1976; Hanson and Goodwin, 1977; Willis and Berrigan, 1977). Temperatures of 22-32” C are necessary for adequate growth (Ling, 1969), which means that lower winter temperatures in the continental United States limit the growing season of prawns in outdoor pond culture. In South Carolina, for example, pond cultivation is restricted to the period from late April to mid-October (Sandifer and Smith, 1976). Animals stocked in April in this region may still be subjected tmcold shock in the event of a late cold front. Little information is available on the cold tolerance of Macrobrachium
250
rosenbergi& Farmanfarmaian (1975) described the ‘critical temperature minimum’ of 20”Cacclimated adult prawns as 125°C. Uno et al. (1975) were able to acclimate some juveniles to 14.3”C for 3 days, but stated that mortality was high below 15” C. Sandifer and Smith (in Goodwin and Hanson, 1975) observed that prawns in the field survived 16°C for several days but they showed some mortality when temperatures dipped to 14” C. The present study was conducted as part of an interdisciplinary program concerning the development of Macrobruchium aquaculture in South Carolina (Sandifer and Smith, 1976). Our experiments were designed to test the survival of post-larval juveniles at 16” C and after short exposure to 13°C. Prawns were acclimated to several temperatures to determine whether animals reared in the laboratory at 27°C would benefit from pre-acclimation to lower temperatures prior to being stocked in ponds in spring. A second series of experiments followed the growth of cold-stressed shrimp once they had been returned to a near-optimum temperature (27°C). MATERIALS
AND METHODS
Post-larval Macrobruchium rosenbergii (laboratory-reared at 27” C and 20/o. and averaging 10 mg each) of the Anuenue (or Fujimura) strain (Malecha, 1977) were obtained from the Macrobrachium aquaculture program of the South Carolina Marine Resources Research Institute. After transfer to our laboratory, the prawns were acclimated for 1 week to 27°C or 22°C and salinity of 5,8, or 14 o/oo (Instant Ocean sea salts in deionized water). Groups of 20 animals were held in 22.5 X 30.5 X 10 cm covered plastic boxes containing about 4.5 1 of water (stocking density of 291 animals/m2 bottom area). To minimize aggression and cannibalism at these high stocking densities, free-form hoops and fences of plastic screening were placed in each box to provide additional surface area and habitat. Boxes held at 22°C and above were aerated. The post-larvae were fed three times a week with an experimental shrimp food obtained from Ralston Purina Company (Marine Ration 25), supplemented by frozen Artemia Water was changed three times a week. The first series of experiments tested the effect of acclimation temperature on the survival of cold-stressed prawns at 16°C and 13°C. Boxes of animals acclimated to 27”C, 22”C, or 16°C were placed in incubators at 16°C for 1 week, or at 13°C for 24 h followed by 16°C for 6 days. Mortality was assessed after 1 week in the experimental regime. The second series of experiments was-designed to determine the effect of transient cold stress on growth. The.experimental design is shown in Table I. Cold-stressed animals were exposed to,a total of 2 weeks at 22°C 20 days at 16”C, and 1 clay at 13°C before being returned to the control temperature of 27°C. A group weight for each box was obtained weekly and from it the average weight per shrimp calculated.
251
TABLE I Experimental design of the growth experiment Week
Control animals
1 2 3 4
27” C
5 6 7-9
t 27°C
Experimental animals 22°C 16°C 16°C 13°C for 1 day 1 16” C for 6 days 22°C 27°C 27°C
RESULTS
Results of the survival study are shown in Fig. 1. Since there were different numbers of replicates in each block, experiments were pooled to give total percent survival for each set of treatments. Following arc-sine transformation, the data were analyzed by two-way and three-way analysis of variance without replication (Sokal and Rohlf, 1969). Experimental
Fig. 1. Survival of M. rosenbergii
Temperature
exposed to cold at three salinities. *Number of animals.
252
The three-way (experimental temperature X acclimation temperature X salinity) analysis of variance indicated significant (P = 0.05) interaction of acclimation and experimental temperatures. Salinity did not significantly interact with either temperature factor. Two-way (acclimation temperature X salinity) analysis of variance of the results for the 16” C experimental group showed no significant effect of either acclimation temperature or salinity. For the 13” C animals, the same test gave a significant (P = 0.05) effect of acclimation temperature but not of salinity. Although the tests employed indicated that salinity effects were not statis tically significant, the lowest salinity (50/o. ) was associated with higher mortality in the most stressful experiments (27” C to 16°C; 27°C and 22°C to 13°C) (Fig. 1). Growth rates of the M. rosenbergii post-larvae were calculated by linear regression analysis and expressed as mg animal-’ week-’ . Although growth overall follows a logarithmic pattern, growth rate was linear for the small time interval (4 weeks) used here; all regression coefficients for the calculated lines were > 0.95. A break in linearity occurred at about 100 mg weight, so the groups of shrimp were divided after the experiments into weight classes (10-100 mg, and 50-200 mg) based on their weight range during the experiments. Each group contained a minimum of 40 animals. The prawns exhibited no growth at temperatures below 22’C. At 27” C there was no significant difference between the growth rates of the experimental and control groups for any of the salinities tested (Table II). Thus, there was no inhibition of growth by 3-weeks exposure to 16°C in the experimental group. The 1977 control group at 5°/oo did show significantly (P = 0.05) faster growth than the equivalent control group tested in 1976. The reason for this difference is not known. TABLE II
Growth (mg/week) of Macrobrachium Group 1976
1977
Salinity (“/,,)
rosenbergii
after cold stress
Controla
ExperimentaIb
Weight (mg)
14
9.2 + 1.3c 14.8 * 2.4 8.9 f 2.3
19.1 f 2,3d 8.3 f 4.ld 11.2 * 4.9d
10-100 50-200 10-100 10-100
5 8 14
18.9 f 3.9 17.7 f 3.1 13.1 + 2.3
23.5 + 9.1* 13.0 t 4.7 12.3 f 1.4df
10-100 10-100
5
10-100
aMaintained at 27” C throughout study. bSee Table I. c95% confidence interval. dNot significantly different from controls. eSignificantiy different (P = 0.05) from equivalent 1976 group. fSignificantly different (P = 0.05) from 1977 5’/,, experimental group.
253
DISCUSSION
The survival of Mucrobrachium rosenbergii subjected to cold shock is influenced by the previous acclimation temperature of the animals. Increased survival with decreased acclimation temperature is most obvious when prawns are subjected to 13”C, but was also observed among the animals subjected to 16°C at 50/oo. Shrimp acclimated to 27°C showed 60% mortality after exposure to 16°C for 1 week, while the group which was pre-acclimated to 22°C for a week prior to the 16°C stress had only 26% mortality. M. rosenbergii larvae are generally reared to the post-larval stage under temperature and salinity conditions of = 28°C and 12-16 ‘loo (Sandifer et al., 1977). Since pond water temperatures in the continental United States are generally considerably cooler than 28” C in spring, when pond stocking occurs and there is always the danger of a late cold front, it might be advantageous to pre-condition the prawns to cooler temperatures prior to stocking them outdoors. The increased resistance to cold with lower acclimation temperatures is consistent with other data available for M. rosenbergii (Farmanfarmaian, 1975; Uno et al., 1975) and with the physiological response of poikilotherms in general (Vernberg and Vernberg, 1970). There is a genetic lower lethal limit below which animals cannot be successfully acclimated, but the 16°C temperature used in our experiments seems to be above the minimum for M. rosenbergii. Caution should be used in extrapolating these data to larger animals, as it is not unusual for different stages in the life cycle to show varying resistance to temperature (cf. Wiesepape, 1975). We examined the effect of salinity on cold tolerance, since it has been shown to affect resistance to thermal extremes in a variety of animals (Vernberg and Silverthorn, 1978). We found no significant effect of salinity on survival, although the prawns subjected to the most severe temperature shock at the lowest salinity (50/o. ) had higher mortality than the corresponding animals at 8 and 140ho. This is consistent with the observation that survival of estuarine animals in cold extremes may be enhanced by higher salinities (Theede, 1973). Our study showed a tendency for growth rate to decrease with increased salinity over a 4-week period. This decrease was statistically significant only in the 14’ho experimental group (1977) when compared to the 5°/oo group. Perdue and Nakamura (1976) found a significant drop in growth rate in juvenile prawns in 15 and 8.5 o/oo,respectively, when compared to salinities of 0 and 2’ho over a lo-week period. The data in this study support the observation that cold is a major factor limiting Mucrobruchium rosenbergii aquaculture in the continental United States. In areas where outdoor pond culture is restricted to the warmer months, it may be advantageous to pre-acclimate post-larvae to cooler temperatures in the laboratory prior to stocking. This should enhance survival
254
and increase the resistance of the prawns to a transient cold snap after they are in the ponds. Although there is no growth at 16°C animals held at that temperature for up to 3 weeks show no adverse effects on their later growth. This fact might allow early stocking so that laboratory facilities could be used for a second group. Although we are able to manipulate the cold tolerance of M. rosenbergii within a narrow range, the lower limit of the prawn’s resistance to cold is ultimately a genetic trait. The most reasonable solution to the temperature limitation placed on aquaculture programs is likely the development of a Macrobrachium hybrid, produced from crossing M. rosenbergii with a suitable indigenous, cold-tolerant American species. ACKNOWLEDGEMENT
We thank Dr. P.A. Sandifer for reviewing the manuscript. REFERENCES Farmanfarmaian, A., 1975. Integration of Thermal and Food Processing Residuals into a System for Commercial Culture of Fresh Water Shrimp. Report to the National Science Foundation, Program of Research Applied to National Needs, on Grant NSF/RANN GI-43925,25 pp. Goodwin, H.L. and Hanson, J.A., 1975. The Aquaculture of Freshwater Prawns (Macrobrachium Species). Augmented Summary of Proceedings of the Workshop on Culture of Freshwater Prawns, St, Petersburg, Fla., November, 1974. The Oceanic Institute, Waimanalo, Hawaii, 95 pp. Hanson, J.A. and Goodwin, H.L., (Editors), 1977. Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., 429 pp. Ling, S.W., 1969. The general biology and development of Macrobrachium rosenbergii (De Man). FAO Fish. Rep., (57) 3 : 589-606. Ling, S.W. and Costello, T.J., 1976. Review of Culture of Freshwater Prawns. FAO Technical Conference on Aquaculture, Kyoto, Japan, May 26-June 2, 1976. FIR:AQ/Conf/76/R.29, 12 pp. Malecha, S.R., 1977. Genetics and selective breeding of M. rosenbergii. In: J.A. Hanson and H.L. Goodwin (Editors), Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., pp. 328-351. Perdue, J.A. Nakamura, R., 1976. The effect of salinity on the growth of Akrobruchium rosenbergii. Proc, 7th Annu. Meet World Mariculture Sot., pp. 647-654. Sandifer, P.A. and Smith, T.I.J., 1976. Experimental Aquaculture of the Malaysian Prawn, Macrobrachium rosenbergii (De Man), in South Carolina, U.S.A. FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June, 1976, FIR:AQ/Conf l76lE.3, 7 pp. Sandifer, P.A., Hopkins, J.S. and Smith, T.I.J., 1977. Production of juveniles: status of Macrobrachium hatcheries, 1976. In : J.A. Hanson and H.L. Goodwin (Editors), Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., pp. 220-231. Sokal, R.R. and Rohlf, F.J., 1969. Biometry: the principles and practices of statistics in biological research. W.H. Freeman & Company, San Francisco, Calif., 776 pp. Theede, H., 1973. Resistance adaptations of marine invertebrates and fish to cold. In: W. Wieser (Editor), Effects of Temperature on Ectothermic Organisms. Springer Verlag, New York, N.Y., pp. 249-270.
255
Uno, Y., Bejie, A.B. and Igarashi, Y., 1975. Effects of temperature on the activity of Macrobrachium rosenbergii. La Mer, 13: 38-42. Vernberg, F.J. and Silverthorn, S.U., 1978. Temperature and osmoregulation in aquatic species. In: R. Gilles (Editor), Mechanisms of Osmoregulation in Animals. Wiley-Interscience, New York, N.Y., in press. Vernberg, F.J. and Vernberg, W.B., 1970. The Animal and the Environment. Holt, Rhinehart & Winston, Inc., New York, N.Y., 398 pp. Wiesepape, L.M., 1975. Thermal Resistance and Acclimation Rate in Young White and Brown Shrimp, Penaeus setiferus Linn and Peneaeus aztecus Ives. Texas A & M University, Sea Grant Publ. TAMU SG-76-202, 196 pp. Willis, S.A. and Berrigan, M.E., 1977. Effects of stocking size and density on growth and survival of Macrobrachium rosenbergii (De Man) in ponds. Proc. World Mariculture Sot., 8: in press.
249
COLD TOLERANCE AT THREE SALINITIES IN POST-LARVAL PRAWNS, MACROBRACHIUM ROSENBERGII (DE MAN)
S. UNGLAUB SILVERTHORN* Department
and ANNE M. REESE
of Physiology, Medical University of South Carolina, Charleston, S. C.
29402 (U.S.A.) *Present address: Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston, Texas 77550 (U.S.A.) This work was sponsored by N.O.A.A., under grant number 04-6-158-44096.
Office of Sea Grant, Department of Commerce,
(Received 22 April 1978; revised 2 August 1978)
ABSTRACT Silverthorn, S. U. and Reese, A.M., 1978. Cold tolerance at three salinities in post-larval prawns, Macrobrachium rosenbergii (De Man). Aquaculture, 15: 249-255. Post-larval Macrobrachium rosenbergii acclimated to 27, 22, or 16°C and 5, 8, or 14 “/,,, were temperature-shocked to 16°C or 13” /lS”C for 1 week. Survival was significantly better in animals acclimated to 22” C or below. Salinity had no significant effect on survival. Growth of post-larvae which had been maintained at 16°C or below for 3 weeks was followed for 1 month at 27” C; it was not significantly different from that of 27” C controls. Slower growth was observed in the 14’/,, prawns. These data indicate that postlarvae stocked into cool ponds from warm hatcheries might benefit from pre-acclimation to lower temperatures. Exposure to cold does not adversely affect later growth.
INTRODUCTION
The giant Malaysian prawn, Mucrobruchium rosenbergii, is currently under investigation as a candidate for aquaculture in many areas of the world, including the continental United States (Goodwin and Hanson, 1975; Ling and Costello, 1976; Sandifer and Smith, 1976; Hanson and Goodwin, 1977; Willis and Berrigan, 1977). Temperatures of 22-32” C are necessary for adequate growth (Ling, 1969), which means that lower winter temperatures in the continental United States limit the growing season of prawns in outdoor pond culture. In South Carolina, for example, pond cultivation is restricted to the period from late April to mid-October (Sandifer and Smith, 1976). Animals stocked in April in this region may still be subjected tmcold shock in the event of a late cold front. Little information is available on the cold tolerance of Macrobrachium
250
rosenbergi& Farmanfarmaian (1975) described the ‘critical temperature minimum’ of 20”Cacclimated adult prawns as 125°C. Uno et al. (1975) were able to acclimate some juveniles to 14.3”C for 3 days, but stated that mortality was high below 15” C. Sandifer and Smith (in Goodwin and Hanson, 1975) observed that prawns in the field survived 16°C for several days but they showed some mortality when temperatures dipped to 14” C. The present study was conducted as part of an interdisciplinary program concerning the development of Macrobruchium aquaculture in South Carolina (Sandifer and Smith, 1976). Our experiments were designed to test the survival of post-larval juveniles at 16” C and after short exposure to 13°C. Prawns were acclimated to several temperatures to determine whether animals reared in the laboratory at 27°C would benefit from pre-acclimation to lower temperatures prior to being stocked in ponds in spring. A second series of experiments followed the growth of cold-stressed shrimp once they had been returned to a near-optimum temperature (27°C). MATERIALS
AND METHODS
Post-larval Macrobruchium rosenbergii (laboratory-reared at 27” C and 20/o. and averaging 10 mg each) of the Anuenue (or Fujimura) strain (Malecha, 1977) were obtained from the Macrobrachium aquaculture program of the South Carolina Marine Resources Research Institute. After transfer to our laboratory, the prawns were acclimated for 1 week to 27°C or 22°C and salinity of 5,8, or 14 o/oo (Instant Ocean sea salts in deionized water). Groups of 20 animals were held in 22.5 X 30.5 X 10 cm covered plastic boxes containing about 4.5 1 of water (stocking density of 291 animals/m2 bottom area). To minimize aggression and cannibalism at these high stocking densities, free-form hoops and fences of plastic screening were placed in each box to provide additional surface area and habitat. Boxes held at 22°C and above were aerated. The post-larvae were fed three times a week with an experimental shrimp food obtained from Ralston Purina Company (Marine Ration 25), supplemented by frozen Artemia Water was changed three times a week. The first series of experiments tested the effect of acclimation temperature on the survival of cold-stressed prawns at 16°C and 13°C. Boxes of animals acclimated to 27”C, 22”C, or 16°C were placed in incubators at 16°C for 1 week, or at 13°C for 24 h followed by 16°C for 6 days. Mortality was assessed after 1 week in the experimental regime. The second series of experiments was-designed to determine the effect of transient cold stress on growth. The.experimental design is shown in Table I. Cold-stressed animals were exposed to,a total of 2 weeks at 22°C 20 days at 16”C, and 1 clay at 13°C before being returned to the control temperature of 27°C. A group weight for each box was obtained weekly and from it the average weight per shrimp calculated.
251
TABLE I Experimental design of the growth experiment Week
Control animals
1 2 3 4
27” C
5 6 7-9
t 27°C
Experimental animals 22°C 16°C 16°C 13°C for 1 day 1 16” C for 6 days 22°C 27°C 27°C
RESULTS
Results of the survival study are shown in Fig. 1. Since there were different numbers of replicates in each block, experiments were pooled to give total percent survival for each set of treatments. Following arc-sine transformation, the data were analyzed by two-way and three-way analysis of variance without replication (Sokal and Rohlf, 1969). Experimental
Fig. 1. Survival of M. rosenbergii
Temperature
exposed to cold at three salinities. *Number of animals.
252
The three-way (experimental temperature X acclimation temperature X salinity) analysis of variance indicated significant (P = 0.05) interaction of acclimation and experimental temperatures. Salinity did not significantly interact with either temperature factor. Two-way (acclimation temperature X salinity) analysis of variance of the results for the 16” C experimental group showed no significant effect of either acclimation temperature or salinity. For the 13” C animals, the same test gave a significant (P = 0.05) effect of acclimation temperature but not of salinity. Although the tests employed indicated that salinity effects were not statis tically significant, the lowest salinity (50/o. ) was associated with higher mortality in the most stressful experiments (27” C to 16°C; 27°C and 22°C to 13°C) (Fig. 1). Growth rates of the M. rosenbergii post-larvae were calculated by linear regression analysis and expressed as mg animal-’ week-’ . Although growth overall follows a logarithmic pattern, growth rate was linear for the small time interval (4 weeks) used here; all regression coefficients for the calculated lines were > 0.95. A break in linearity occurred at about 100 mg weight, so the groups of shrimp were divided after the experiments into weight classes (10-100 mg, and 50-200 mg) based on their weight range during the experiments. Each group contained a minimum of 40 animals. The prawns exhibited no growth at temperatures below 22’C. At 27” C there was no significant difference between the growth rates of the experimental and control groups for any of the salinities tested (Table II). Thus, there was no inhibition of growth by 3-weeks exposure to 16°C in the experimental group. The 1977 control group at 5°/oo did show significantly (P = 0.05) faster growth than the equivalent control group tested in 1976. The reason for this difference is not known. TABLE II
Growth (mg/week) of Macrobrachium Group 1976
1977
Salinity (“/,,)
rosenbergii
after cold stress
Controla
ExperimentaIb
Weight (mg)
14
9.2 + 1.3c 14.8 * 2.4 8.9 f 2.3
19.1 f 2,3d 8.3 f 4.ld 11.2 * 4.9d
10-100 50-200 10-100 10-100
5 8 14
18.9 f 3.9 17.7 f 3.1 13.1 + 2.3
23.5 + 9.1* 13.0 t 4.7 12.3 f 1.4df
10-100 10-100
5
10-100
aMaintained at 27” C throughout study. bSee Table I. c95% confidence interval. dNot significantly different from controls. eSignificantiy different (P = 0.05) from equivalent 1976 group. fSignificantly different (P = 0.05) from 1977 5’/,, experimental group.
253
DISCUSSION
The survival of Mucrobrachium rosenbergii subjected to cold shock is influenced by the previous acclimation temperature of the animals. Increased survival with decreased acclimation temperature is most obvious when prawns are subjected to 13”C, but was also observed among the animals subjected to 16°C at 50/oo. Shrimp acclimated to 27°C showed 60% mortality after exposure to 16°C for 1 week, while the group which was pre-acclimated to 22°C for a week prior to the 16°C stress had only 26% mortality. M. rosenbergii larvae are generally reared to the post-larval stage under temperature and salinity conditions of = 28°C and 12-16 ‘loo (Sandifer et al., 1977). Since pond water temperatures in the continental United States are generally considerably cooler than 28” C in spring, when pond stocking occurs and there is always the danger of a late cold front, it might be advantageous to pre-condition the prawns to cooler temperatures prior to stocking them outdoors. The increased resistance to cold with lower acclimation temperatures is consistent with other data available for M. rosenbergii (Farmanfarmaian, 1975; Uno et al., 1975) and with the physiological response of poikilotherms in general (Vernberg and Vernberg, 1970). There is a genetic lower lethal limit below which animals cannot be successfully acclimated, but the 16°C temperature used in our experiments seems to be above the minimum for M. rosenbergii. Caution should be used in extrapolating these data to larger animals, as it is not unusual for different stages in the life cycle to show varying resistance to temperature (cf. Wiesepape, 1975). We examined the effect of salinity on cold tolerance, since it has been shown to affect resistance to thermal extremes in a variety of animals (Vernberg and Silverthorn, 1978). We found no significant effect of salinity on survival, although the prawns subjected to the most severe temperature shock at the lowest salinity (50/o. ) had higher mortality than the corresponding animals at 8 and 140ho. This is consistent with the observation that survival of estuarine animals in cold extremes may be enhanced by higher salinities (Theede, 1973). Our study showed a tendency for growth rate to decrease with increased salinity over a 4-week period. This decrease was statistically significant only in the 14’ho experimental group (1977) when compared to the 5°/oo group. Perdue and Nakamura (1976) found a significant drop in growth rate in juvenile prawns in 15 and 8.5 o/oo,respectively, when compared to salinities of 0 and 2’ho over a lo-week period. The data in this study support the observation that cold is a major factor limiting Mucrobruchium rosenbergii aquaculture in the continental United States. In areas where outdoor pond culture is restricted to the warmer months, it may be advantageous to pre-acclimate post-larvae to cooler temperatures in the laboratory prior to stocking. This should enhance survival
254
and increase the resistance of the prawns to a transient cold snap after they are in the ponds. Although there is no growth at 16°C animals held at that temperature for up to 3 weeks show no adverse effects on their later growth. This fact might allow early stocking so that laboratory facilities could be used for a second group. Although we are able to manipulate the cold tolerance of M. rosenbergii within a narrow range, the lower limit of the prawn’s resistance to cold is ultimately a genetic trait. The most reasonable solution to the temperature limitation placed on aquaculture programs is likely the development of a Macrobrachium hybrid, produced from crossing M. rosenbergii with a suitable indigenous, cold-tolerant American species. ACKNOWLEDGEMENT
We thank Dr. P.A. Sandifer for reviewing the manuscript. REFERENCES Farmanfarmaian, A., 1975. Integration of Thermal and Food Processing Residuals into a System for Commercial Culture of Fresh Water Shrimp. Report to the National Science Foundation, Program of Research Applied to National Needs, on Grant NSF/RANN GI-43925,25 pp. Goodwin, H.L. and Hanson, J.A., 1975. The Aquaculture of Freshwater Prawns (Macrobrachium Species). Augmented Summary of Proceedings of the Workshop on Culture of Freshwater Prawns, St, Petersburg, Fla., November, 1974. The Oceanic Institute, Waimanalo, Hawaii, 95 pp. Hanson, J.A. and Goodwin, H.L., (Editors), 1977. Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., 429 pp. Ling, S.W., 1969. The general biology and development of Macrobrachium rosenbergii (De Man). FAO Fish. Rep., (57) 3 : 589-606. Ling, S.W. and Costello, T.J., 1976. Review of Culture of Freshwater Prawns. FAO Technical Conference on Aquaculture, Kyoto, Japan, May 26-June 2, 1976. FIR:AQ/Conf/76/R.29, 12 pp. Malecha, S.R., 1977. Genetics and selective breeding of M. rosenbergii. In: J.A. Hanson and H.L. Goodwin (Editors), Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., pp. 328-351. Perdue, J.A. Nakamura, R., 1976. The effect of salinity on the growth of Akrobruchium rosenbergii. Proc, 7th Annu. Meet World Mariculture Sot., pp. 647-654. Sandifer, P.A. and Smith, T.I.J., 1976. Experimental Aquaculture of the Malaysian Prawn, Macrobrachium rosenbergii (De Man), in South Carolina, U.S.A. FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June, 1976, FIR:AQ/Conf l76lE.3, 7 pp. Sandifer, P.A., Hopkins, J.S. and Smith, T.I.J., 1977. Production of juveniles: status of Macrobrachium hatcheries, 1976. In : J.A. Hanson and H.L. Goodwin (Editors), Shrimp and Prawn Farming in the Western Hemisphere. Dowden, Hutchinson & Ross, Inc., Stroudsburg, Pa., pp. 220-231. Sokal, R.R. and Rohlf, F.J., 1969. Biometry: the principles and practices of statistics in biological research. W.H. Freeman & Company, San Francisco, Calif., 776 pp. Theede, H., 1973. Resistance adaptations of marine invertebrates and fish to cold. In: W. Wieser (Editor), Effects of Temperature on Ectothermic Organisms. Springer Verlag, New York, N.Y., pp. 249-270.
255
Uno, Y., Bejie, A.B. and Igarashi, Y., 1975. Effects of temperature on the activity of Macrobrachium rosenbergii. La Mer, 13: 38-42. Vernberg, F.J. and Silverthorn, S.U., 1978. Temperature and osmoregulation in aquatic species. In: R. Gilles (Editor), Mechanisms of Osmoregulation in Animals. Wiley-Interscience, New York, N.Y., in press. Vernberg, F.J. and Vernberg, W.B., 1970. The Animal and the Environment. Holt, Rhinehart & Winston, Inc., New York, N.Y., 398 pp. Wiesepape, L.M., 1975. Thermal Resistance and Acclimation Rate in Young White and Brown Shrimp, Penaeus setiferus Linn and Peneaeus aztecus Ives. Texas A & M University, Sea Grant Publ. TAMU SG-76-202, 196 pp. Willis, S.A. and Berrigan, M.E., 1977. Effects of stocking size and density on growth and survival of Macrobrachium rosenbergii (De Man) in ponds. Proc. World Mariculture Sot., 8: in press.