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Effect of pH and ammonia on survival and growth of the early larval stages of Penaeus monodon Fabricius
ELSEVIER
Aquaculture 125 (1994) 67-72
Effect of pH and ammonia on survival and growth of the early larval stages of Penaeus monodon Fabricius Sutan Noor-Hami@* , Romeo D. Fortesb, Fe Parado-Estepa” “Brackishwater Aquaculture Development Centre, Pemandian Kartini, Jepara 59401, Indonesia bUniversity of the Philippines, Visayas, Miagao-Iloilo 5003, Philippines ‘South East Asian Fisheries Development Centre (SEAFDEC) Aquaculture Department, Iloilo 5028, Philippines
Accepted 1 March 1994
Abstract Lethal toxicity tests of ammonia at different pH levels (7,7.5,8, and 8.5) and its effect on survival and growth of the early larval stages of Penaeus monodon were determined. An increase in ammonia toxicity when the water pH increased was revealed in 96 h toxicity tests. Estimated LTso decreased from 101.09 to 25.16 h for protozoea exposed to 8 ppm ammonia, from 115.79 to 11.26 h for mysis exposed to 24 ppm, and from 51.41 to 22.58 h for PL exposed to 52 ppm ammonia with increase in pH levels. The effect of 3 and 6 ppm ammonia levels at pH levels of 7.0, 7.5, 8.0 and 8.5 on the survival and growth of P. monodon larvae and postlarvae was also investigated in a 16-day sublethal toxicity test. Results indicated that ammonia at 3 and 6 ppm affects both survival and growth of shrimp. Survival was decreased by 27% in 3 ppm and by 48% in 6 ppm ammonia, while growth was reduced by 4.4% in 3 ppm and by 6.5% in 6 ppm ammonia. Increasing pH of the rearing water resulted in significantly lower survival in protozoea, mysis, and postlarval stages. No interactive effect of pH and ammonia was detected.
1. Introduction Ammonia toxicity is known to be one of the common causes of death in fish and shrimp reared in tanks. In the intensive method of rearing shrimp larvae in hatcheries, high concentrations of ammonia could be a potential danger to the cultured animals. Ammonia in water can be either ionized (NH: ) or unionized (NH,), the unionized form being more toxic than the ionized form (Wickins, 1976; Bower and Bidwell, 1978; Boyd, 1982). The *Corresponding author. 0044-8486/94/$07.00
0 1994 Elsevier Science B.V. All rights reserved
SSDIOO44-8486(94)00057-U
68
S. Noor-Hamid etal. /Aquaculture 125 (1994) 67-72
equilibrium between these ammonia forms depends on temperature, salinity and above all the pH of the solution (Whitfield, 1974; Bower and Bidwell, 1978; Boyd, 1982). Catedral et al. ( 1977) reported that ammonia at 10 ppm is toxic to postlarvae (PL) of P. monodon. Further study on ammonia toxicity by Chin and Chen ( 1987) showed that the 24 h L& of ammonia-N were 6, 8, 24 and 52 ppm for nauplius, protozoea, mysis, and postlarva, respectively, of this species. The present study deals with the effect of ammonia at different pH levels on the larvae of P. monodon under controlled conditions. Median lethal time (LT& was determined on larvae at different stages during the lethal toxicity test while survival and growth were compared in a sublethal toxicity test.
2. Materials and methods Lethal toxicity test Static bioassay tests to assess ammonia toxicity of P. monodon at different pH levels were conducted. The shrimp were obtained from the laboratory of the Southeast Asian Fisheries Development Center (SEAFDECYAQD) and from a private hatchery in Iloilo, Philippines. Larvae at the different developmental stages were exposed to different ammonia levels, based on the LC& values determined by Chin and Chen ( 1987)) at pH levels of 7.0, 7.5,8.0 or 8.5. Zoeae were exposed to 8 ppm total ammonia-N (TAN) while mysis and PL were exposed to 24 and 52 ppm TAN respectively. The calculated unionized ammonia at each pH level is shown in Table 1. Each treatment was replicated 3 times. It was not possible to make a control group of each pH level in the experiment but the seawater pH used ranged from 8.1 to 8.3. The different ammonia solutions were prepared by adding ammonium chloride (NH,Cl) to seawater until the desired concentration was attained. Levels of pH were created by the addition of 1N HCL or 1N NaOH. Table 1 Ammonia, pH level and calculated unionized ammonia concentrationsused in the experiment Larvalstage
TAN (ppm)
PH
Unionized (NH,-N) (ppm)
zoea
8
Mysis
24
PL
52
7.0 7.5 8.0 8.5 7.0 7.5 8.0 8.5 7.0 7.5 8.0 8.5
0.05 0.16 0.51 1.40 0.16 0.50 1.53 4.23 0.35 1.09 3.31 9.14
TAN = total ammonia-N (unionized + ionized ammonia)
S. Noor-Hamid et al. /Aquaculture 125 (1994) 67-72
69
Table 2 Absolute values assigned to the respective stages to compute the population stage index Larval stage ZoeaI
Zoea II Zoea III Mysis I Mysis II
Absolute value
Larval stage
Absolute value
Mysis III PLI PL II PL III
6” 7” 8” 9”
“Postlarval substage number was based on the number of meltings and not on the number of days after the larvae metamorphosed to the postIarval stage.
Salinity was maintained at 30 f 2 ppt. Temperature was kept at 28 f 2°C by placing the containers in a waterbath with a thermostat-controlled heater. Levels of ammonia in beakers were determined every morning using the spectrophotometric method described by Strickland and Parson ( 1972), before replacing with fresh solutions. Water pH were monitored using an electronic pH meter and adjusted to test level every 4 h. Active zoea (Zl), mysis (Ml), or postlarvae (PLl) were stocked separately in l-liter glass beakers at a density of 20 individuals/ beaker. The animals were fed with diatom Chaetoceros culcitruns maintained at 30 000 cells/ml by adding new diatom culture every day. The commercially available artificial diet BP-Nippai brand was given at small amount every 6 h. Animals were observed at 2-h intervals during the first 12 h after stocking and every 12 h thereafter for the rest of the 96-h period or until the larvae molted to the next stage. The median lethal time (LT,,) was estimated using probit analysis (Finney, 1952). LT,,s at each stage were compared using ANOVA. Sublethal toxicity test P. monodon zoeae were stocked in 3-liter jars at a density of 20 individuals/l and reared until PL5. Animals were exposed to ammonia at concentration of 3 and 6 ppm TAN. Animals in the control were placed in seawater with no ammonium chloride added. Four levels of pH at each ammonia concentration were maintained: (a) 7.0, (b) 7.5, (c) 8.0 and (d) 8.5. Each treatment was replicated 3 times. Levels of ammonia and pH were obtained using the same procedure as in the lethal toxicity test. Feeding of the larvae was similar to the lethal toxicity test. Water was replaced at 50% daily. Survival in each container was determined at days 7, 10, and 16. Development was assessed by assigning numerical values to each stage (Table 2) and determining the population stage index following the procedure of Villegas and Kanazawa ( 1979). The postlarval substages were indentified according to Motoh ( 1981). Thus, substage number changed only after the postlarva has molted. The survival and computed population stage indices at the different treatments were compared using two-way ANOVA (Gomez and Gomez, 1983). 3. Result and discussion Lethal toxicity test The LT,, obtained at the various treatments are shown in Table 3. At each stage, all LTsos in all treatment were significantly different from each other (P< 0.01). The LT+ at pH 7.0 and 7.5 for the zoea stage were estimated by extrapolation from the survival curve, since
70
S. Noor-Hamid et al. /Aquaculture 125 (1994) 67-72
Table 3 Mean estimated median lethal time (LT,,) in hours) of Penaeus monodon larvae exposed to varying pH levels PH
zoeae (8 ppm)’
7.0 7.5 8.0 8.5
101.09+ 97.17* 85.37f 25.16f
1.26” 1.22b 1.10’ 1.32’
Mysis (24 ppm)’
Postlarvae (52 ppm)’
115.79* 82.65 f 34.12* 11.26 f
51.41 f 39.52 f 24.97* 22.58 f
1.02= 1.05b 1.21’ 4.29’
1.38” 1.27b 1.10’ 1.08’
Mean f se. of 3 replicates is given. Means in the same column with different superscripts are significantly different (P
survival immediately after larvae molted to the mysis stage was 64 and 52%, respectively. A similar trend of decreasing LTso with increasing pH level is reflected at all larval stages. LTso drastically decreased from 101.09 to 25.16 h at the zoea stage, and from 115.79 h to 11.26 h at the mysis stage when the pH increased from 7.0 to 8.5. At the postlarval stage the LT, also decreased significantly, though less drastically, from 51.41 h at pH 7.0 to 22.58 h at pH 8.5. Since a lower LTso value suggests higher toxicity, these results indicate that toxicity of ammonia at any particular concentration increases with increasing pH levels. The estimated LTsOfor postlarvae exposed to a total ammmonia concentration of 52 ppm and pH 8.0 was 24.97 h. This is comparable to the results of Chin and Chen (1987) which gave 52 ppm total ammonia as 24-h LC50 (concentration at which 50% of the population dies after 24 h) at pH 7.8-8.3. Chen and Sheu (1989) also found that toxicity of ammonia to P. japonicus larvae increased as pH increased. Increasing pH by one unit causes a lo-fold increase in the concentration percentage of unionized ammonia (Bower and Bidwell, 1978; Boyd, 1982). The effect of high pH - a high proportion of the unionized form of ammonia - may account for the significant reduction in LTsOvalues. Sublethal toxicity test
Two-way ANOVA of the arcsine-transformed percentage survival at termination of the test (day 16) showed that both pH and ammonia affected survival (P < 0.01) but (P > 0.05) (Tables 4 and 5). Table 4 Percentage survival and growth stage indices of P. monodon postlarvae reared at different pH levels pH level
Survival (%)
Final growth stage index
7.0 7.5 8.0 8.5
12.86 f 2.52’ 28.43 k4.32” 24.60 f4.56* 19.26f2.62bC
8.11 kO.07” 8.15 rtO.12” 8.15f0.11a 7.93 f 0.14’
Mean f se. of 12 pooled observations from the 3 different ammonia levels are given. Means in tbe same column with different superscripts are significantly different (P < 0.01) Percentage survival data were first transformed to arcsines before analysis.
S. Noor-Hamid et al. /Aquaculture
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71
Table 5 Percentage survival and population stage indices (PSI) of P. monodon postlarvae reared at different ammonia levels Ammonia level
Survival (%)
Final growth stage index
Control’ 3 ppm 6 ppm
28.50 f 3.06” 20.60 rt4.34b 14.8Ok 1.14b
8.36 f 0.07” 8.00 f 0.06b 7.88 f 0.06b
Mean f s.e. of 12 pooled observations from the 3 different pH levels are given. Means in the same column with different superscripts am significantly different (P < 0.01) . Percentage survival data were first transformed to arcsines before analysis. ‘Control ammonia level was 0.23 f 0.11 ppm. Survival was highest at pH level of 7.5 and lowest at pH 7.0, although this value was not significantly different from that obtained at pH 8.5 (Table 4). Development stage index did not vary significantly with pH level. These results indicate that at ammonia concentrations of O-6 ppm, P. monodon can survive and develop at pH levels of 7.5-8.0. Parado-Estepa et al. (1990) suggested that pH range of 7.3-8.5 is suitable for shrimp hatchery. During larval rearing, however, pH range must be narrowed to 7.0-8.0 based on the results of the present test. The survival and developmental stage index of P. monodon larvae in the control were significantly higher (P < 0.01) than those obtained in other ammonia test levels. These results indicate that total ammonia concentrations exceeding 3 ppm can reduce survival and retard the growth of P. monodon larvae or postlarvae. In the control the calculated unionized ammonia related to pH ranged from 0.0015 to 0.038 ppm. This level is considered too low to affect larval survival. Regression analysis of unionized ammonia concentration at each treatment against survival and developmental indices showed that survival and growth stage index were not correlated with each other (r = - 0.028; P > 0.05). This further supports the lack of significant interaction between total ammonia and pH within the concentrations tested. Since TAN and pH levels determine the amount of unionized ammonia in the water, some interaction between these two factors is expected. However, the range of unionized amomnia concentration in the test (0.001-l .06 ppm) may have been too narrow to enable detection of such an interaction. The effect of either total ammonia or pH may have been greater and more discernible than the effect of unionized ammonia.
Acknowledgement Sincere appreciation is expressed to FAO-United Shrimp Culture Development Project INS/O85/009.
Nations, Rome, for support under the
References Boyd, CF., 1982. Water Quality Management for Pond Fish Culture. Elsevier, Amsterdam, 303 pp. Bower, J.E. and Bidwell, J.P. 1978. Ionization of ammonia in sea water: Effect of temperature, pH and salinity. J. Fish. Res. Board Can., 35: 1012-1016.
12
S. Noor-Hamid et al. /Aquaculture 125 (1994) 67-72
CatedraI, F.F., Gerochi, D.D., Quibuyen A.T. and Casalmir, C.M., 1977.Effect of nitrite, ammoniaand temperature on Penaeus monodon. Quart. Res. Rep. SEAFDEC Philipp., 3: 9-12. Cben, J.C. and Sbeu, T.S., 1989. Effect of ammonia at different pH on Penaeus japonicus postlarvae. In: J.L. McLean, L.B. Dizon and L.V. Hosillos (Editors), 2nd Asian Fish. Forum. Asian Fish. Sot., Philippines, pp. 61-64. Chin, T.S. and Chen, J.C., 1987. Acute toxicity of ammonia to larvae of tiger prawn Penaeus monodon. Aquaculture, 66: 247-253. Finney, W.D., 1952. Probit Analysis. Cambridge University Press, 633 pp. Gomez, K.A. and Gomez, A.A., 1983. Statistical Procedure for Agricultural Research. IRRI, John Wiley and Sons. Publ., Singapore, 680 pp. Motoh, H., 1981. Study on the fisheries biology of the giant tiger prawn Penaeus monodon in the Philippines. Tech. Rep. 7, SEAFDEC, AQD, Iloilo. Parado-Estepa, F.D., Quinitio, E.T. and Borlongan, E.L., 1990. Prawn hatchery operation. SEAFDEC Ext. Man. 19. Iloilo, 44 pp. Strickland, J.D.H. and Parson, T.R., 1972. A Practical Handbook of Seawater Analysis. Bull. Res. Board Canada, 310 pp. Villegas, C.F. and Kanazawa, V., -1979. Relationship betweeen diet and growth rate of meal and mysis stage of Penaeus japonicus. Fish. Res. J. Philipp., 4( 2) : 32-40. Whitfield, M., 1974. The hydrolysis of ammonium ion in sea water. J. Mar. Biol. Assoc. UK, 54: 565-580. Wickins, J.F., 1976. The tolerance of warm water prawn to recirculated water. Aquaculture, 9: 19-37.
Aquaculture 125 (1994) 67-72
Effect of pH and ammonia on survival and growth of the early larval stages of Penaeus monodon Fabricius Sutan Noor-Hami@* , Romeo D. Fortesb, Fe Parado-Estepa” “Brackishwater Aquaculture Development Centre, Pemandian Kartini, Jepara 59401, Indonesia bUniversity of the Philippines, Visayas, Miagao-Iloilo 5003, Philippines ‘South East Asian Fisheries Development Centre (SEAFDEC) Aquaculture Department, Iloilo 5028, Philippines
Accepted 1 March 1994
Abstract Lethal toxicity tests of ammonia at different pH levels (7,7.5,8, and 8.5) and its effect on survival and growth of the early larval stages of Penaeus monodon were determined. An increase in ammonia toxicity when the water pH increased was revealed in 96 h toxicity tests. Estimated LTso decreased from 101.09 to 25.16 h for protozoea exposed to 8 ppm ammonia, from 115.79 to 11.26 h for mysis exposed to 24 ppm, and from 51.41 to 22.58 h for PL exposed to 52 ppm ammonia with increase in pH levels. The effect of 3 and 6 ppm ammonia levels at pH levels of 7.0, 7.5, 8.0 and 8.5 on the survival and growth of P. monodon larvae and postlarvae was also investigated in a 16-day sublethal toxicity test. Results indicated that ammonia at 3 and 6 ppm affects both survival and growth of shrimp. Survival was decreased by 27% in 3 ppm and by 48% in 6 ppm ammonia, while growth was reduced by 4.4% in 3 ppm and by 6.5% in 6 ppm ammonia. Increasing pH of the rearing water resulted in significantly lower survival in protozoea, mysis, and postlarval stages. No interactive effect of pH and ammonia was detected.
1. Introduction Ammonia toxicity is known to be one of the common causes of death in fish and shrimp reared in tanks. In the intensive method of rearing shrimp larvae in hatcheries, high concentrations of ammonia could be a potential danger to the cultured animals. Ammonia in water can be either ionized (NH: ) or unionized (NH,), the unionized form being more toxic than the ionized form (Wickins, 1976; Bower and Bidwell, 1978; Boyd, 1982). The *Corresponding author. 0044-8486/94/$07.00
0 1994 Elsevier Science B.V. All rights reserved
SSDIOO44-8486(94)00057-U
68
S. Noor-Hamid etal. /Aquaculture 125 (1994) 67-72
equilibrium between these ammonia forms depends on temperature, salinity and above all the pH of the solution (Whitfield, 1974; Bower and Bidwell, 1978; Boyd, 1982). Catedral et al. ( 1977) reported that ammonia at 10 ppm is toxic to postlarvae (PL) of P. monodon. Further study on ammonia toxicity by Chin and Chen ( 1987) showed that the 24 h L& of ammonia-N were 6, 8, 24 and 52 ppm for nauplius, protozoea, mysis, and postlarva, respectively, of this species. The present study deals with the effect of ammonia at different pH levels on the larvae of P. monodon under controlled conditions. Median lethal time (LT& was determined on larvae at different stages during the lethal toxicity test while survival and growth were compared in a sublethal toxicity test.
2. Materials and methods Lethal toxicity test Static bioassay tests to assess ammonia toxicity of P. monodon at different pH levels were conducted. The shrimp were obtained from the laboratory of the Southeast Asian Fisheries Development Center (SEAFDECYAQD) and from a private hatchery in Iloilo, Philippines. Larvae at the different developmental stages were exposed to different ammonia levels, based on the LC& values determined by Chin and Chen ( 1987)) at pH levels of 7.0, 7.5,8.0 or 8.5. Zoeae were exposed to 8 ppm total ammonia-N (TAN) while mysis and PL were exposed to 24 and 52 ppm TAN respectively. The calculated unionized ammonia at each pH level is shown in Table 1. Each treatment was replicated 3 times. It was not possible to make a control group of each pH level in the experiment but the seawater pH used ranged from 8.1 to 8.3. The different ammonia solutions were prepared by adding ammonium chloride (NH,Cl) to seawater until the desired concentration was attained. Levels of pH were created by the addition of 1N HCL or 1N NaOH. Table 1 Ammonia, pH level and calculated unionized ammonia concentrationsused in the experiment Larvalstage
TAN (ppm)
PH
Unionized (NH,-N) (ppm)
zoea
8
Mysis
24
PL
52
7.0 7.5 8.0 8.5 7.0 7.5 8.0 8.5 7.0 7.5 8.0 8.5
0.05 0.16 0.51 1.40 0.16 0.50 1.53 4.23 0.35 1.09 3.31 9.14
TAN = total ammonia-N (unionized + ionized ammonia)
S. Noor-Hamid et al. /Aquaculture 125 (1994) 67-72
69
Table 2 Absolute values assigned to the respective stages to compute the population stage index Larval stage ZoeaI
Zoea II Zoea III Mysis I Mysis II
Absolute value
Larval stage
Absolute value
Mysis III PLI PL II PL III
6” 7” 8” 9”
“Postlarval substage number was based on the number of meltings and not on the number of days after the larvae metamorphosed to the postIarval stage.
Salinity was maintained at 30 f 2 ppt. Temperature was kept at 28 f 2°C by placing the containers in a waterbath with a thermostat-controlled heater. Levels of ammonia in beakers were determined every morning using the spectrophotometric method described by Strickland and Parson ( 1972), before replacing with fresh solutions. Water pH were monitored using an electronic pH meter and adjusted to test level every 4 h. Active zoea (Zl), mysis (Ml), or postlarvae (PLl) were stocked separately in l-liter glass beakers at a density of 20 individuals/ beaker. The animals were fed with diatom Chaetoceros culcitruns maintained at 30 000 cells/ml by adding new diatom culture every day. The commercially available artificial diet BP-Nippai brand was given at small amount every 6 h. Animals were observed at 2-h intervals during the first 12 h after stocking and every 12 h thereafter for the rest of the 96-h period or until the larvae molted to the next stage. The median lethal time (LT,,) was estimated using probit analysis (Finney, 1952). LT,,s at each stage were compared using ANOVA. Sublethal toxicity test P. monodon zoeae were stocked in 3-liter jars at a density of 20 individuals/l and reared until PL5. Animals were exposed to ammonia at concentration of 3 and 6 ppm TAN. Animals in the control were placed in seawater with no ammonium chloride added. Four levels of pH at each ammonia concentration were maintained: (a) 7.0, (b) 7.5, (c) 8.0 and (d) 8.5. Each treatment was replicated 3 times. Levels of ammonia and pH were obtained using the same procedure as in the lethal toxicity test. Feeding of the larvae was similar to the lethal toxicity test. Water was replaced at 50% daily. Survival in each container was determined at days 7, 10, and 16. Development was assessed by assigning numerical values to each stage (Table 2) and determining the population stage index following the procedure of Villegas and Kanazawa ( 1979). The postlarval substages were indentified according to Motoh ( 1981). Thus, substage number changed only after the postlarva has molted. The survival and computed population stage indices at the different treatments were compared using two-way ANOVA (Gomez and Gomez, 1983). 3. Result and discussion Lethal toxicity test The LT,, obtained at the various treatments are shown in Table 3. At each stage, all LTsos in all treatment were significantly different from each other (P< 0.01). The LT+ at pH 7.0 and 7.5 for the zoea stage were estimated by extrapolation from the survival curve, since
70
S. Noor-Hamid et al. /Aquaculture 125 (1994) 67-72
Table 3 Mean estimated median lethal time (LT,,) in hours) of Penaeus monodon larvae exposed to varying pH levels PH
zoeae (8 ppm)’
7.0 7.5 8.0 8.5
101.09+ 97.17* 85.37f 25.16f
1.26” 1.22b 1.10’ 1.32’
Mysis (24 ppm)’
Postlarvae (52 ppm)’
115.79* 82.65 f 34.12* 11.26 f
51.41 f 39.52 f 24.97* 22.58 f
1.02= 1.05b 1.21’ 4.29’
1.38” 1.27b 1.10’ 1.08’
Mean f se. of 3 replicates is given. Means in the same column with different superscripts are significantly different (P
survival immediately after larvae molted to the mysis stage was 64 and 52%, respectively. A similar trend of decreasing LTso with increasing pH level is reflected at all larval stages. LTso drastically decreased from 101.09 to 25.16 h at the zoea stage, and from 115.79 h to 11.26 h at the mysis stage when the pH increased from 7.0 to 8.5. At the postlarval stage the LT, also decreased significantly, though less drastically, from 51.41 h at pH 7.0 to 22.58 h at pH 8.5. Since a lower LTso value suggests higher toxicity, these results indicate that toxicity of ammonia at any particular concentration increases with increasing pH levels. The estimated LTsOfor postlarvae exposed to a total ammmonia concentration of 52 ppm and pH 8.0 was 24.97 h. This is comparable to the results of Chin and Chen (1987) which gave 52 ppm total ammonia as 24-h LC50 (concentration at which 50% of the population dies after 24 h) at pH 7.8-8.3. Chen and Sheu (1989) also found that toxicity of ammonia to P. japonicus larvae increased as pH increased. Increasing pH by one unit causes a lo-fold increase in the concentration percentage of unionized ammonia (Bower and Bidwell, 1978; Boyd, 1982). The effect of high pH - a high proportion of the unionized form of ammonia - may account for the significant reduction in LTsOvalues. Sublethal toxicity test
Two-way ANOVA of the arcsine-transformed percentage survival at termination of the test (day 16) showed that both pH and ammonia affected survival (P < 0.01) but (P > 0.05) (Tables 4 and 5). Table 4 Percentage survival and growth stage indices of P. monodon postlarvae reared at different pH levels pH level
Survival (%)
Final growth stage index
7.0 7.5 8.0 8.5
12.86 f 2.52’ 28.43 k4.32” 24.60 f4.56* 19.26f2.62bC
8.11 kO.07” 8.15 rtO.12” 8.15f0.11a 7.93 f 0.14’
Mean f se. of 12 pooled observations from the 3 different ammonia levels are given. Means in tbe same column with different superscripts are significantly different (P < 0.01) Percentage survival data were first transformed to arcsines before analysis.
S. Noor-Hamid et al. /Aquaculture
I25 (1994) 67-72
71
Table 5 Percentage survival and population stage indices (PSI) of P. monodon postlarvae reared at different ammonia levels Ammonia level
Survival (%)
Final growth stage index
Control’ 3 ppm 6 ppm
28.50 f 3.06” 20.60 rt4.34b 14.8Ok 1.14b
8.36 f 0.07” 8.00 f 0.06b 7.88 f 0.06b
Mean f s.e. of 12 pooled observations from the 3 different pH levels are given. Means in the same column with different superscripts am significantly different (P < 0.01) . Percentage survival data were first transformed to arcsines before analysis. ‘Control ammonia level was 0.23 f 0.11 ppm. Survival was highest at pH level of 7.5 and lowest at pH 7.0, although this value was not significantly different from that obtained at pH 8.5 (Table 4). Development stage index did not vary significantly with pH level. These results indicate that at ammonia concentrations of O-6 ppm, P. monodon can survive and develop at pH levels of 7.5-8.0. Parado-Estepa et al. (1990) suggested that pH range of 7.3-8.5 is suitable for shrimp hatchery. During larval rearing, however, pH range must be narrowed to 7.0-8.0 based on the results of the present test. The survival and developmental stage index of P. monodon larvae in the control were significantly higher (P < 0.01) than those obtained in other ammonia test levels. These results indicate that total ammonia concentrations exceeding 3 ppm can reduce survival and retard the growth of P. monodon larvae or postlarvae. In the control the calculated unionized ammonia related to pH ranged from 0.0015 to 0.038 ppm. This level is considered too low to affect larval survival. Regression analysis of unionized ammonia concentration at each treatment against survival and developmental indices showed that survival and growth stage index were not correlated with each other (r = - 0.028; P > 0.05). This further supports the lack of significant interaction between total ammonia and pH within the concentrations tested. Since TAN and pH levels determine the amount of unionized ammonia in the water, some interaction between these two factors is expected. However, the range of unionized amomnia concentration in the test (0.001-l .06 ppm) may have been too narrow to enable detection of such an interaction. The effect of either total ammonia or pH may have been greater and more discernible than the effect of unionized ammonia.
Acknowledgement Sincere appreciation is expressed to FAO-United Shrimp Culture Development Project INS/O85/009.
Nations, Rome, for support under the
References Boyd, CF., 1982. Water Quality Management for Pond Fish Culture. Elsevier, Amsterdam, 303 pp. Bower, J.E. and Bidwell, J.P. 1978. Ionization of ammonia in sea water: Effect of temperature, pH and salinity. J. Fish. Res. Board Can., 35: 1012-1016.
12
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CatedraI, F.F., Gerochi, D.D., Quibuyen A.T. and Casalmir, C.M., 1977.Effect of nitrite, ammoniaand temperature on Penaeus monodon. Quart. Res. Rep. SEAFDEC Philipp., 3: 9-12. Cben, J.C. and Sbeu, T.S., 1989. Effect of ammonia at different pH on Penaeus japonicus postlarvae. In: J.L. McLean, L.B. Dizon and L.V. Hosillos (Editors), 2nd Asian Fish. Forum. Asian Fish. Sot., Philippines, pp. 61-64. Chin, T.S. and Chen, J.C., 1987. Acute toxicity of ammonia to larvae of tiger prawn Penaeus monodon. Aquaculture, 66: 247-253. Finney, W.D., 1952. Probit Analysis. Cambridge University Press, 633 pp. Gomez, K.A. and Gomez, A.A., 1983. Statistical Procedure for Agricultural Research. IRRI, John Wiley and Sons. Publ., Singapore, 680 pp. Motoh, H., 1981. Study on the fisheries biology of the giant tiger prawn Penaeus monodon in the Philippines. Tech. Rep. 7, SEAFDEC, AQD, Iloilo. Parado-Estepa, F.D., Quinitio, E.T. and Borlongan, E.L., 1990. Prawn hatchery operation. SEAFDEC Ext. Man. 19. Iloilo, 44 pp. Strickland, J.D.H. and Parson, T.R., 1972. A Practical Handbook of Seawater Analysis. Bull. Res. Board Canada, 310 pp. Villegas, C.F. and Kanazawa, V., -1979. Relationship betweeen diet and growth rate of meal and mysis stage of Penaeus japonicus. Fish. Res. J. Philipp., 4( 2) : 32-40. Whitfield, M., 1974. The hydrolysis of ammonium ion in sea water. J. Mar. Biol. Assoc. UK, 54: 565-580. Wickins, J.F., 1976. The tolerance of warm water prawn to recirculated water. Aquaculture, 9: 19-37.