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The reproductive performance of wild and pondreared Penaeus semisulcatus de Haan
Aquaculture, 59 (1986) 251-258 Elsevier Science Publishers B.V., Amsterdam -
251 Primed in The Netherlands
The Reproductive Performance of Wild and Pondreared Penaeus semisulcatus De Haan CRAIG L. BROWDY1r2 ALIZA HADANP, TSACHI M. SAMOCHA’ and YOSSI LOYA’ ‘Israel Oceanographic and Limnological Research Institute, National Center for Mariculture, P.O.B. 1212, Eilat 88112 (Israel) ‘Tel Aviv University, George S. Wise Faculty of Life Sciences, Department of Zoology, Ramat Aviv, 69978 Tel Aviv ,(Israel) (Accepted 13 August 1986)
ABSTRACT Browdy, C.L., Hadani, A., Samocha, T.M. and Loya, Y., 1986. The reproductive performance of wild and pond-reared Penaeus semisulcatus de Haan. Aquaculture, 59: 251-258. A controlled comparison of the reproductive performance of individually tagged wild (PO) and first generation pond-reared (Pl) Penaeus semisulcatus is presented. Eyestalk ablated and nonablated females matured and spawned in 3-m3 maturation tanks. Females which had undergone unilateral eyestalk ablation showed: (1) a slower growth rate (g/day) ; (2) a trend towards shortening of the molt cycle; (3) a significantly smaller number of eggs and nauplii per spawn; and (4 ) significantly increased spawn frequency and increased rate of egg and nauplii production. The fertility and hatchability of spawns from ablated females were not different from those of spawns from nonablated females. All of these trends were observed for both PO and Pl spawners. The average spawn from a Pl female had fewer eggs than the average spawn from a PO female. Fertility and hatchability of spawns from both generations were variable and no significant difference was found in the number of nauplii in an average spawn. No significant differences were found between the two generations in the average number of spawns, eggs and nauplii produced per day. Thus the reproductive potential of Pl broodstock was not different from that of PO females induced to mature and spawn in captivity.
INTRODUCTION
Over the past 15 years an intensive research effort has been directed towards the controlled husbandry of marine penaeid shrimp. Recognition of the necessity to complete the life cycle in captivity has led to the successful maturation and spawning of around 14 penaeid species (Primavera, 1985). Since 1983, controlled reproduction of captive Penaeus semisukuttls has been achieved year round at the National Center for Mariculture in Eilat, Israel (Browdy and &mocha, 1985a). The production of successive generations of broodstock in captivity is crucial 0044-8486/86/$03.50
0 1986 Elsevier Science Publishers B.V.
252
for a number of reasons. Firstly, collection of penaeid broodstock from the sea is both costly and unreliable. Secondly, the introduction of fungal, bacterial or viral disease organisms is a potential hazard which requires expensive, timeconsuming and, at times, fallible counter-measures. Finally, the development of selective breeding, hybridization and other genetic programs depends on technology for the rearing of successive generations of high quality genetic stock. Larvae have been reared from captive Pl broodstock reared in captivity for several penaeid species including: Penueus aztecus (AQUACOP, 1977); P. juponicus (Laubier-3onichon, 1975; AQUACOP, 1977; Lumare, 1981) ; P. merguiensis (AQUACOP, 1975; Beard et al., 1977) ; P. monodon (AQUACOP, 1979); P. stylirostris (AQUACOP, 1979; Brown et al., 1985); P. vannamei (AQUACOP, 1979). In a previous paper, we reported the successful rearing of two generations of P. semisuZcatus broodstock (Browdy and Samocha, 1985a) and we have since collected viable spawns from third generation pond-reared (P3) females. To date, no controlled comparison of fecundity has been made between successive generations of spawners. The aim of this study is, therefore, to compare the reproductive performance of wild broodstock (PO) with that of first generation pond-reared broodstock (Pl ) in a controlled experimental system. MATERIALSAND METHODS Adult Penueus semisulcatus were collected from an eastern Mediterranean spawning ground in May 1984. The Pl broodstock were reared from the first spawn collected from three of these females (all of which had mated in the wild). Larvae were cultured at a density of 100/l according to the Galveston method with some local modifications (Mock et al., 1980). They were fed on the algae Chuetoceros gracilis and Tetraselmis chuii, the rotifer Brachionus plicatilis, and nauplii of Artemia salinu in accordance with their developmental stage. Postlarvae were transferred to nursery tanks and were reared to 500 mg at a density of 2500/m3. During this period the animals were fed on live nauplii and frozen adult Artemiu salinu and ground, frozen seafood with a dry pelleted feed added as a supplement. Nine hundred animals were then transferred to an earthen pond for grow&out.The pond was rectangular with gradually sloping sides to a maximum depth of 1 m, a surface area of 325 m2, and a volume of 175 m3. Water temperatures ranged from a maximum summer temperature of 32 oC to a minimum temperature of 13 oC in winter. Frozen seafood was the principal diet, with a dry pelleted feed added as a supplement. In May 1985, Pl females were transferred from the pond for the experiment and fresh PO animals were again brought from the same spawning ground. From each generation 21 females were placed into three circular maturation tanks (7 females into each tank). Twelve females from each group (four per
253
tank) were chosen at random and were unilaterally ablated using an electrocautery apparatus. Females which died during the first 2 weeks were replaced. Six males (PO) were also stocked into each tank, yielding a female to male ratio of 2.33:1. Each maturation tank had black walls and a white bottom and contained 3 m3 of water attaining a depth of 80 cm. All tanks were shaded and partially covered with a black plastic mesh to decrease illumination to 0.1-0.3 PE m2 s-l. Flow rates were held at 5 l/min. Salinity and pH were constant at 40 ppt and 8.2, respectively. Dissolved oxygen ranged from 6.1 to 7.7 ppm. Temperature ranged from a daily minimum of 22.2 ‘C-25.0’ C to a daily maximum of 23.O”C-265°C. The animals were fed twice daily. Food provided in the morning consisted of frozen adult Artemiu dim and in the late afternoon frozen fish and frozen squid were offered. Every 10 days nitrofurazone bath treatments (5 ppm over 1 h) were given to prevent possible bacterial infection. The maturation, spawning, molting and mating of each individual female were monitored daily. Females were marked by placing a numbered ring around the eyestalk and making coded cuts in one or more of the four uropoda, allowing identification of fresh molts and individuals in the tanks. On a daily basis, molts were identified and freshly molted females were checked for evidence of spermatophore transfer. In addition, the degree of ovarian maturation was checked each afternoon by external macroscopic examination of the color and size of the developing ovaries. Females with ripe ovaries were removed to separate spawning tanks. When a spawn was detected, eggs and nauplii were counted using aliquot samples. Methodological details have been reported in a previous publication (Browdy and Samocha, 1985b). Wet weight was measured upon stocking and at the end of the 40-day experimental period. Data from the three maturation tanks were pooled according to treatment and generation. Statistical analyses were carried out using a two-way analysis of variance of the effects of broodstock generation and the ablation treatment ( Walonick, 1984). RESULTS
The initial weights of the females in each group are presented in Table 1. The overall average weight for ablated females and nonablated females was 40.2% 5.6 g and 40.724.1 g, respectively. The average weight of PO and Pl females was 41.6 + 5.5 g and 39.2 -I-3.6 g, respectively. No significant differences in weight were found between these groups, The growth rate (mg/day ) was calculated for each female individually. No significant difference in the average growth rate over the two generations was found (PC 0.05) ; however, the ablated females grew almost three times slower than the nonablated females (PC 0.05, Table 1) . By the end of the experiment the condition of ablated
254 TABLE 1 Weight, growth, molting and mating of Penaeus semisulcatus spawners Ablated PO Average initial weight (g)b Av. growth rate (mg/day)’ Av. length of the molt cycle (days) =sd Spermatophore transfer success ( % ) dr
41.6 f 3.8 (11) 2.2k8.1 21.5t-3.4 (6) 93.75 (16)
Nonablated Pl 38.9 + 3.9 (13) 2.0a6.6 21.7k2.3 (6) 100.00 (17)
Significance”
PQ
Pl
PO/P1
Ab./Nab.
41.7k7.0 (12) 8.6k5.7
39.6k3.1 (10) 5.927.4
P>O.O5
P>O.O5
P>O.O5
P
22.6f 1.5 (5) 71.43
23.6f1.5 (5) 90.91
(14)
-
-
(11)
“Two-way analysis of variance (WaIonick, 1984). t-standard Nab. = nonablated, PO=wiId, Pl = Pond reared. bNumber of animals measured in parentheses. “Calculated only for females which survived 10 days or more. dInsufficient data for statistical analysis. “Number of molts in parentheses.
deviation.
Ab.=Ablated,
females was poorer than that of nonablated females (as evidenced by black spots, a loss of equilibrium, loss of appendages, short antennules, etc. ) . The average length of the molt cycle calculated for females which molted twice over the course of the experiment is presented in Table 1. In 52 out of 58 cases (89.7%)) freshly molted females had received spermatophores. Nonablated females were less successful in mating than ablated females. The total percentage of spermatophore transfer for each group is given in Table 1. Table 2 summarizes the average size, fertility and hatchability of spawns from ablated and nonablated females belonging to the PO and Pl generations. The average spawn from a PO female was somewhat larger than the size of an average spawn from a pond-reared female (PC 0.05). The average spawn from a nonablated female was significantly larger than the average spawn from an ablated female (P < 0.05). The rates of fertilization and hatching were variable and no significant differences were found between the groups (P> 0.05). No significant difference was found in the average number of nauplii per spawn between generations (P> 0.05) ; however, a significant reduction in the average number of nauplii per spawn was observed for ablated females (PC 0.05). Table 3 provides the results concerning the average daily rate of spawning, egg and nauplii production per female. The rate of reproduction (the average number of spawnings per female per day and the average number of eggs and nauplii produced per female per day) was faster for ablated females (PC 0.05) while no significant differences were found between generations (P> 0.05). The total cumulative egg production per female is shown in Fig. 1.
255 TABLE 2 Average size, fertility, and hatchability of spawns from Penaeus semisulcatus Ablated
Av. number of eggs/spawn ( f 103) Av. % fertility Av. number of nauplii/spawn ( X 103) Av. % hatch
Nonablated
Significance”
PO
Pl
PO
Pl
PO/P1
Ab./Nab.
89.2rt33.9
17.4k30.5
113.6f46.0
97.9t-17.8
P
P
68.6f27.1 49.2k38.4
i’5.8f23.4 52.8k27.2
83.6k14.4 85.8k48.5
72.7k24.5 63.6k29.0
P>O.O5 P>O.O5
P>O.O5 P
65.8228.9
82.4kl3.4
83.7k15.5
71.6k28.8
P>O.O5
P>O.O5
“Two-way analysis of variance (Walonick, 1984). Nab. = nonablated, PO= wild, Pl = pond reared.
31standard deviation.
Ab. = Ablated,
DISCUSSION
The relationship between reproduction and growth is dependent upon the division of energy resources between these processes. At the same time each is dependent on the size and condition of the animal. In the present experiment, growth rate was found to be slower for ablated animals. This could be related to increased reproductive rate or to a reduction in the health or condition of the ablated females. The increase in weight was, however, very small and further research with larger numbers of animals and careful control for weighing errors is needed before positive conclusions can be reached. In the present experiment, nonablated females were somewhat less successful in mating than ablated females while in previous studies the opposite relationship was observed (Browdy and Samocha, 198513). More research into factors affecting mating TABLE 3 Average daily rate of spawning, egg and nauplii production per female Penaeus semisulcatus Nonablated
Ablated PO Av. number of spawns/day Av. number of eggs/day ( x lo3 ) Av. number of nauplii/day (x103)
0.13f0.06 12.8 f8.3 6.0 +4.8
Significance”
Pl
PO
Pl
PO/P1
Ab./Nab.
0.13+0.07
0.04+0.04
0.07?0.04
P>O.O5
Pt0.01
9.6 +7.5
3.7 k4.1
6.5 k5.0
P>O.O5
P
5.8 f4.5
2.8 23.3
4.1 +3.3
P>O.O5
P=O.O5
“Two-way analysis of variance ( WaIonick, 1984). Nab. = nonablated, PO= wild, Pl =pond reared.
t-standard
deviation.
Ab. = Ablated,
256
0
10
20
30
40
DRYS Fig. 1. Cumulative eggproduction per female Penaeus semisulcatus. 0 = Ablated, PO; X = ablated, PI; Y = nonablated, PO;* = nonablated, Pl.
success in closed thelycum penaeids is necessary to optimize spermatophore transfer in captivity. Results of comparisons between ablated and nonablated females documented in previous experiments (Browdy and Samocha, 1985a,b) were again observed in this study. An apparent trend towards a shortening of the molt cycle of ablated females was evident and spawn frequency and corresponding egg and nauplii production were significantly increased for ablated females. These effects are presumably due to the decrease in the levels of hormones .which inhibit molting (MIH) and gonad development (GIH) ( Adiyodi, 1985). Similarly, the results on spawn size and percent hatch, for ablated and nonablated broodstock, parallelled those reported in our papers cited above. The average spawn from an ablated female had significantly fewer eggs and nauplii than the average spawn from a nonablated female and hatchability of spawns from ablated females was as high as that of spontaneous spawns. These trends were similar for both PO and Pl broodstock. The effects of the rearing of broodstock in captivity on spawn quality and spawn frequency is not clear. Some authors have reported no reduction in fecundity (AQUACOP, 1979) while others have reported on trends toward reduced spawn size (Mock, 1971; Browdy and Samocha, 1985a). The present study is a controlled comparison based on a first generation pond-reared broodstock grown at a low density and fed a diet based on fresh or frozen seafood throughout the life cycle. The reduction in the size of spawns from pond-
257
reared broodstock was small but significant. Variability in percent fertility and percent hatch, however, all but masked the trend completely as no significant difference was found in the number of nauplii per spawn. Differences in average initial weight were very small while the variation within groups was-large. Therefore it is unlikely that differences in initial weight could account for the reduction observed in the size of spawns from Pl females. This trend suggests that the rearing techniques used were less than optimal. Broodstock diet and rearing conditions could have an important effect on reproductive fitness. More research into this area is necessary to insure multiple generations of high quality broodstock. Despite the reduction in the number of eggs per spawn, the average number of spawns, eggs and nauplii produced per day and the overall total egg production from Pl broodstock were not significantly different from the PO broodstock (P> 0.05). This indicates that the reproductive potential of the first generation of captive broodstock is not different from that of females brought from the sea and induced to mature and spawn in captivity. This can be of great importance in relieving the dependence of commercial maturation facilities on wild spawners. A small number of PO can be used to produce a large Pl breeding stock. These broodstock can then be used to produce the massive quantities of eggs needed for stocking modern commercial hatcheries.
REFERENCES Adiyodi, R.G., 1985. Reproduction and its control. In: D.E. Bliss and L.H. Mantel (Editors), Crustacea, Vol. 9. Integument, Pigments, and Hormonal Processes. Academic Press Inc., New York, NY, pp. 147-215. AQUACOP, 1975. Maturation and spawning in captivity of penaeid shrimp Penaeus merguiensis de Man, Penaeus japonicus Bate, Penaeus aztecus Ives, Metapenaeus ensis de Haan, and Penaeus semisulcatus de Haan. J. World Maricult. Sot., 6: 123-132. AQUACOP, 1977. Reproduction in captivity and growth of Penaeus monodon, Fabricus in Polynesia. J. World Maricult. Sot., 8: 927-945. AQUACOP, 1979. Penaeid reared broodstock: closing the cycle of P. monodon, P. stylirostris and P. vannamei. J. World Ma&&. Sot., 10: 445-452. Beard, T.W., Wickins, J.F. and Arnstein, D.R., 1977. The breeding and growth of Penaew merguiensis de Man in laboratory recirculation systems. Aquaculture, 10: 275-289. Browdy, C.L. and &mocha, T.M., 1985a. Maturation and spawning of ablated and nonablated Penaeus semisulcatus de Haan, 1844. J. World Maricult. Sot., 16: 236-249. Browdy, C.L. and &mocha, T.M., 1985b. The effect of eyestalk ablation on spawning, molting and mating of Penaezu semisulcatus de Haan. Aquaculture, 48: 19-29. Brown, A. Jr., Tave, D., Williams, T.D. and Duronslet, M.J., 1985. Production of second generation penaeid shrimp, Penaeus stylirostris, fromMexico. Aquaculture, 41: 81-84. Laubier-Bonichon, A., 1975. Induction de la maturation sexuelle et ponte chez la crevette Penaeus japonicus Bate en milieu contr5le. C. R. Acad. Sci. Paris, 281(3) : 2013-2016. Lumare, F., 1981. Artificial reproduction of Penaeus japonicw Bate as a basis for the mass production of eggs and larvae. J. World Maricult. Sot., I2 (2) : 335-344.
Mock, C.R., 1971. Crustacean culture. In: W.N. Shaw (Editor), Proc. First U.S.-Japan Meeting on Aquaculture, Tokyo, Japan, 1971. NOAA Rep. NMFS CIRC 388, pp. 111-113. Mock, C.R., Revera, D.B. and Fontaine, C.T., 1980. The larval culture of Penuew stylirostris using modifications of the Galveston laboratory technique. J. World Maricult. Sot., 7: 102-117. Primavera, J.H., 1985. A review of maturation and reproduction in closed thelycum penaeids. In: Y. Taki, J. H. Primavera and J.A. Llobrera (Editors), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, Philippines, 1984. Aquaculture Dept., Southeast Asian Fisheries Development Center, pp. 47-64. Walonick, D.S., 1984. Statpac - Statistical Analysis Package. Price Waterhouse Associates, Ont., pp. l-100.
251 Primed in The Netherlands
The Reproductive Performance of Wild and Pondreared Penaeus semisulcatus De Haan CRAIG L. BROWDY1r2 ALIZA HADANP, TSACHI M. SAMOCHA’ and YOSSI LOYA’ ‘Israel Oceanographic and Limnological Research Institute, National Center for Mariculture, P.O.B. 1212, Eilat 88112 (Israel) ‘Tel Aviv University, George S. Wise Faculty of Life Sciences, Department of Zoology, Ramat Aviv, 69978 Tel Aviv ,(Israel) (Accepted 13 August 1986)
ABSTRACT Browdy, C.L., Hadani, A., Samocha, T.M. and Loya, Y., 1986. The reproductive performance of wild and pond-reared Penaeus semisulcatus de Haan. Aquaculture, 59: 251-258. A controlled comparison of the reproductive performance of individually tagged wild (PO) and first generation pond-reared (Pl) Penaeus semisulcatus is presented. Eyestalk ablated and nonablated females matured and spawned in 3-m3 maturation tanks. Females which had undergone unilateral eyestalk ablation showed: (1) a slower growth rate (g/day) ; (2) a trend towards shortening of the molt cycle; (3) a significantly smaller number of eggs and nauplii per spawn; and (4 ) significantly increased spawn frequency and increased rate of egg and nauplii production. The fertility and hatchability of spawns from ablated females were not different from those of spawns from nonablated females. All of these trends were observed for both PO and Pl spawners. The average spawn from a Pl female had fewer eggs than the average spawn from a PO female. Fertility and hatchability of spawns from both generations were variable and no significant difference was found in the number of nauplii in an average spawn. No significant differences were found between the two generations in the average number of spawns, eggs and nauplii produced per day. Thus the reproductive potential of Pl broodstock was not different from that of PO females induced to mature and spawn in captivity.
INTRODUCTION
Over the past 15 years an intensive research effort has been directed towards the controlled husbandry of marine penaeid shrimp. Recognition of the necessity to complete the life cycle in captivity has led to the successful maturation and spawning of around 14 penaeid species (Primavera, 1985). Since 1983, controlled reproduction of captive Penaeus semisukuttls has been achieved year round at the National Center for Mariculture in Eilat, Israel (Browdy and &mocha, 1985a). The production of successive generations of broodstock in captivity is crucial 0044-8486/86/$03.50
0 1986 Elsevier Science Publishers B.V.
252
for a number of reasons. Firstly, collection of penaeid broodstock from the sea is both costly and unreliable. Secondly, the introduction of fungal, bacterial or viral disease organisms is a potential hazard which requires expensive, timeconsuming and, at times, fallible counter-measures. Finally, the development of selective breeding, hybridization and other genetic programs depends on technology for the rearing of successive generations of high quality genetic stock. Larvae have been reared from captive Pl broodstock reared in captivity for several penaeid species including: Penueus aztecus (AQUACOP, 1977); P. juponicus (Laubier-3onichon, 1975; AQUACOP, 1977; Lumare, 1981) ; P. merguiensis (AQUACOP, 1975; Beard et al., 1977) ; P. monodon (AQUACOP, 1979); P. stylirostris (AQUACOP, 1979; Brown et al., 1985); P. vannamei (AQUACOP, 1979). In a previous paper, we reported the successful rearing of two generations of P. semisuZcatus broodstock (Browdy and Samocha, 1985a) and we have since collected viable spawns from third generation pond-reared (P3) females. To date, no controlled comparison of fecundity has been made between successive generations of spawners. The aim of this study is, therefore, to compare the reproductive performance of wild broodstock (PO) with that of first generation pond-reared broodstock (Pl ) in a controlled experimental system. MATERIALSAND METHODS Adult Penueus semisulcatus were collected from an eastern Mediterranean spawning ground in May 1984. The Pl broodstock were reared from the first spawn collected from three of these females (all of which had mated in the wild). Larvae were cultured at a density of 100/l according to the Galveston method with some local modifications (Mock et al., 1980). They were fed on the algae Chuetoceros gracilis and Tetraselmis chuii, the rotifer Brachionus plicatilis, and nauplii of Artemia salinu in accordance with their developmental stage. Postlarvae were transferred to nursery tanks and were reared to 500 mg at a density of 2500/m3. During this period the animals were fed on live nauplii and frozen adult Artemiu salinu and ground, frozen seafood with a dry pelleted feed added as a supplement. Nine hundred animals were then transferred to an earthen pond for grow&out.The pond was rectangular with gradually sloping sides to a maximum depth of 1 m, a surface area of 325 m2, and a volume of 175 m3. Water temperatures ranged from a maximum summer temperature of 32 oC to a minimum temperature of 13 oC in winter. Frozen seafood was the principal diet, with a dry pelleted feed added as a supplement. In May 1985, Pl females were transferred from the pond for the experiment and fresh PO animals were again brought from the same spawning ground. From each generation 21 females were placed into three circular maturation tanks (7 females into each tank). Twelve females from each group (four per
253
tank) were chosen at random and were unilaterally ablated using an electrocautery apparatus. Females which died during the first 2 weeks were replaced. Six males (PO) were also stocked into each tank, yielding a female to male ratio of 2.33:1. Each maturation tank had black walls and a white bottom and contained 3 m3 of water attaining a depth of 80 cm. All tanks were shaded and partially covered with a black plastic mesh to decrease illumination to 0.1-0.3 PE m2 s-l. Flow rates were held at 5 l/min. Salinity and pH were constant at 40 ppt and 8.2, respectively. Dissolved oxygen ranged from 6.1 to 7.7 ppm. Temperature ranged from a daily minimum of 22.2 ‘C-25.0’ C to a daily maximum of 23.O”C-265°C. The animals were fed twice daily. Food provided in the morning consisted of frozen adult Artemiu dim and in the late afternoon frozen fish and frozen squid were offered. Every 10 days nitrofurazone bath treatments (5 ppm over 1 h) were given to prevent possible bacterial infection. The maturation, spawning, molting and mating of each individual female were monitored daily. Females were marked by placing a numbered ring around the eyestalk and making coded cuts in one or more of the four uropoda, allowing identification of fresh molts and individuals in the tanks. On a daily basis, molts were identified and freshly molted females were checked for evidence of spermatophore transfer. In addition, the degree of ovarian maturation was checked each afternoon by external macroscopic examination of the color and size of the developing ovaries. Females with ripe ovaries were removed to separate spawning tanks. When a spawn was detected, eggs and nauplii were counted using aliquot samples. Methodological details have been reported in a previous publication (Browdy and Samocha, 1985b). Wet weight was measured upon stocking and at the end of the 40-day experimental period. Data from the three maturation tanks were pooled according to treatment and generation. Statistical analyses were carried out using a two-way analysis of variance of the effects of broodstock generation and the ablation treatment ( Walonick, 1984). RESULTS
The initial weights of the females in each group are presented in Table 1. The overall average weight for ablated females and nonablated females was 40.2% 5.6 g and 40.724.1 g, respectively. The average weight of PO and Pl females was 41.6 + 5.5 g and 39.2 -I-3.6 g, respectively. No significant differences in weight were found between these groups, The growth rate (mg/day ) was calculated for each female individually. No significant difference in the average growth rate over the two generations was found (PC 0.05) ; however, the ablated females grew almost three times slower than the nonablated females (PC 0.05, Table 1) . By the end of the experiment the condition of ablated
254 TABLE 1 Weight, growth, molting and mating of Penaeus semisulcatus spawners Ablated PO Average initial weight (g)b Av. growth rate (mg/day)’ Av. length of the molt cycle (days) =sd Spermatophore transfer success ( % ) dr
41.6 f 3.8 (11) 2.2k8.1 21.5t-3.4 (6) 93.75 (16)
Nonablated Pl 38.9 + 3.9 (13) 2.0a6.6 21.7k2.3 (6) 100.00 (17)
Significance”
PQ
Pl
PO/P1
Ab./Nab.
41.7k7.0 (12) 8.6k5.7
39.6k3.1 (10) 5.927.4
P>O.O5
P>O.O5
P>O.O5
P
22.6f 1.5 (5) 71.43
23.6f1.5 (5) 90.91
(14)
-
-
(11)
“Two-way analysis of variance (WaIonick, 1984). t-standard Nab. = nonablated, PO=wiId, Pl = Pond reared. bNumber of animals measured in parentheses. “Calculated only for females which survived 10 days or more. dInsufficient data for statistical analysis. “Number of molts in parentheses.
deviation.
Ab.=Ablated,
females was poorer than that of nonablated females (as evidenced by black spots, a loss of equilibrium, loss of appendages, short antennules, etc. ) . The average length of the molt cycle calculated for females which molted twice over the course of the experiment is presented in Table 1. In 52 out of 58 cases (89.7%)) freshly molted females had received spermatophores. Nonablated females were less successful in mating than ablated females. The total percentage of spermatophore transfer for each group is given in Table 1. Table 2 summarizes the average size, fertility and hatchability of spawns from ablated and nonablated females belonging to the PO and Pl generations. The average spawn from a PO female was somewhat larger than the size of an average spawn from a pond-reared female (PC 0.05). The average spawn from a nonablated female was significantly larger than the average spawn from an ablated female (P < 0.05). The rates of fertilization and hatching were variable and no significant differences were found between the groups (P> 0.05). No significant difference was found in the average number of nauplii per spawn between generations (P> 0.05) ; however, a significant reduction in the average number of nauplii per spawn was observed for ablated females (PC 0.05). Table 3 provides the results concerning the average daily rate of spawning, egg and nauplii production per female. The rate of reproduction (the average number of spawnings per female per day and the average number of eggs and nauplii produced per female per day) was faster for ablated females (PC 0.05) while no significant differences were found between generations (P> 0.05). The total cumulative egg production per female is shown in Fig. 1.
255 TABLE 2 Average size, fertility, and hatchability of spawns from Penaeus semisulcatus Ablated
Av. number of eggs/spawn ( f 103) Av. % fertility Av. number of nauplii/spawn ( X 103) Av. % hatch
Nonablated
Significance”
PO
Pl
PO
Pl
PO/P1
Ab./Nab.
89.2rt33.9
17.4k30.5
113.6f46.0
97.9t-17.8
P
P
68.6f27.1 49.2k38.4
i’5.8f23.4 52.8k27.2
83.6k14.4 85.8k48.5
72.7k24.5 63.6k29.0
P>O.O5 P>O.O5
P>O.O5 P
65.8228.9
82.4kl3.4
83.7k15.5
71.6k28.8
P>O.O5
P>O.O5
“Two-way analysis of variance (Walonick, 1984). Nab. = nonablated, PO= wild, Pl = pond reared.
31standard deviation.
Ab. = Ablated,
DISCUSSION
The relationship between reproduction and growth is dependent upon the division of energy resources between these processes. At the same time each is dependent on the size and condition of the animal. In the present experiment, growth rate was found to be slower for ablated animals. This could be related to increased reproductive rate or to a reduction in the health or condition of the ablated females. The increase in weight was, however, very small and further research with larger numbers of animals and careful control for weighing errors is needed before positive conclusions can be reached. In the present experiment, nonablated females were somewhat less successful in mating than ablated females while in previous studies the opposite relationship was observed (Browdy and Samocha, 198513). More research into factors affecting mating TABLE 3 Average daily rate of spawning, egg and nauplii production per female Penaeus semisulcatus Nonablated
Ablated PO Av. number of spawns/day Av. number of eggs/day ( x lo3 ) Av. number of nauplii/day (x103)
0.13f0.06 12.8 f8.3 6.0 +4.8
Significance”
Pl
PO
Pl
PO/P1
Ab./Nab.
0.13+0.07
0.04+0.04
0.07?0.04
P>O.O5
Pt0.01
9.6 +7.5
3.7 k4.1
6.5 k5.0
P>O.O5
P
5.8 f4.5
2.8 23.3
4.1 +3.3
P>O.O5
P=O.O5
“Two-way analysis of variance ( WaIonick, 1984). Nab. = nonablated, PO= wild, Pl =pond reared.
t-standard
deviation.
Ab. = Ablated,
256
0
10
20
30
40
DRYS Fig. 1. Cumulative eggproduction per female Penaeus semisulcatus. 0 = Ablated, PO; X = ablated, PI; Y = nonablated, PO;* = nonablated, Pl.
success in closed thelycum penaeids is necessary to optimize spermatophore transfer in captivity. Results of comparisons between ablated and nonablated females documented in previous experiments (Browdy and Samocha, 1985a,b) were again observed in this study. An apparent trend towards a shortening of the molt cycle of ablated females was evident and spawn frequency and corresponding egg and nauplii production were significantly increased for ablated females. These effects are presumably due to the decrease in the levels of hormones .which inhibit molting (MIH) and gonad development (GIH) ( Adiyodi, 1985). Similarly, the results on spawn size and percent hatch, for ablated and nonablated broodstock, parallelled those reported in our papers cited above. The average spawn from an ablated female had significantly fewer eggs and nauplii than the average spawn from a nonablated female and hatchability of spawns from ablated females was as high as that of spontaneous spawns. These trends were similar for both PO and Pl broodstock. The effects of the rearing of broodstock in captivity on spawn quality and spawn frequency is not clear. Some authors have reported no reduction in fecundity (AQUACOP, 1979) while others have reported on trends toward reduced spawn size (Mock, 1971; Browdy and Samocha, 1985a). The present study is a controlled comparison based on a first generation pond-reared broodstock grown at a low density and fed a diet based on fresh or frozen seafood throughout the life cycle. The reduction in the size of spawns from pond-
257
reared broodstock was small but significant. Variability in percent fertility and percent hatch, however, all but masked the trend completely as no significant difference was found in the number of nauplii per spawn. Differences in average initial weight were very small while the variation within groups was-large. Therefore it is unlikely that differences in initial weight could account for the reduction observed in the size of spawns from Pl females. This trend suggests that the rearing techniques used were less than optimal. Broodstock diet and rearing conditions could have an important effect on reproductive fitness. More research into this area is necessary to insure multiple generations of high quality broodstock. Despite the reduction in the number of eggs per spawn, the average number of spawns, eggs and nauplii produced per day and the overall total egg production from Pl broodstock were not significantly different from the PO broodstock (P> 0.05). This indicates that the reproductive potential of the first generation of captive broodstock is not different from that of females brought from the sea and induced to mature and spawn in captivity. This can be of great importance in relieving the dependence of commercial maturation facilities on wild spawners. A small number of PO can be used to produce a large Pl breeding stock. These broodstock can then be used to produce the massive quantities of eggs needed for stocking modern commercial hatcheries.
REFERENCES Adiyodi, R.G., 1985. Reproduction and its control. In: D.E. Bliss and L.H. Mantel (Editors), Crustacea, Vol. 9. Integument, Pigments, and Hormonal Processes. Academic Press Inc., New York, NY, pp. 147-215. AQUACOP, 1975. Maturation and spawning in captivity of penaeid shrimp Penaeus merguiensis de Man, Penaeus japonicus Bate, Penaeus aztecus Ives, Metapenaeus ensis de Haan, and Penaeus semisulcatus de Haan. J. World Maricult. Sot., 6: 123-132. AQUACOP, 1977. Reproduction in captivity and growth of Penaeus monodon, Fabricus in Polynesia. J. World Maricult. Sot., 8: 927-945. AQUACOP, 1979. Penaeid reared broodstock: closing the cycle of P. monodon, P. stylirostris and P. vannamei. J. World Ma&&. Sot., 10: 445-452. Beard, T.W., Wickins, J.F. and Arnstein, D.R., 1977. The breeding and growth of Penaew merguiensis de Man in laboratory recirculation systems. Aquaculture, 10: 275-289. Browdy, C.L. and &mocha, T.M., 1985a. Maturation and spawning of ablated and nonablated Penaeus semisulcatus de Haan, 1844. J. World Maricult. Sot., 16: 236-249. Browdy, C.L. and &mocha, T.M., 1985b. The effect of eyestalk ablation on spawning, molting and mating of Penaezu semisulcatus de Haan. Aquaculture, 48: 19-29. Brown, A. Jr., Tave, D., Williams, T.D. and Duronslet, M.J., 1985. Production of second generation penaeid shrimp, Penaeus stylirostris, fromMexico. Aquaculture, 41: 81-84. Laubier-Bonichon, A., 1975. Induction de la maturation sexuelle et ponte chez la crevette Penaeus japonicus Bate en milieu contr5le. C. R. Acad. Sci. Paris, 281(3) : 2013-2016. Lumare, F., 1981. Artificial reproduction of Penaeus japonicw Bate as a basis for the mass production of eggs and larvae. J. World Maricult. Sot., I2 (2) : 335-344.
Mock, C.R., 1971. Crustacean culture. In: W.N. Shaw (Editor), Proc. First U.S.-Japan Meeting on Aquaculture, Tokyo, Japan, 1971. NOAA Rep. NMFS CIRC 388, pp. 111-113. Mock, C.R., Revera, D.B. and Fontaine, C.T., 1980. The larval culture of Penuew stylirostris using modifications of the Galveston laboratory technique. J. World Maricult. Sot., 7: 102-117. Primavera, J.H., 1985. A review of maturation and reproduction in closed thelycum penaeids. In: Y. Taki, J. H. Primavera and J.A. Llobrera (Editors), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, Philippines, 1984. Aquaculture Dept., Southeast Asian Fisheries Development Center, pp. 47-64. Walonick, D.S., 1984. Statpac - Statistical Analysis Package. Price Waterhouse Associates, Ont., pp. l-100.