The study was conducted at the Central Experimental Station, Philippine Rice Research Institute, Maligaya, Science City of Munoz, Nueva Ecija, Philippines during the wet season to determine the suitable stocking density(s) for better growth and yield of fish under rice-fish production systems. Recovery rate of GIFT tilapia in different stocking densities ranged from 75.74 to 83.47%. Among different treatments, rice +5,000 fingerlings/ha and rice +10,000 fingerlings/ha resulted in the highest recovery rate of 83.33% and 83.47%, respectively. The lowest recovery rate of 75.75% was obtained from rice +20,000 fingerlings/ha, but similar to that was obtained (78.56%) from rice +15,000 fingerlings/ha. Significantly higher rate of gain in body weight and that of specific growth rate were recorded in the treatment from rice +5,000 fingerlings/ha, while other treatments resulted in similar absolute and specific growth rate. Fish yield increased significantly with relatively higher stocking densities, but higher densities produced maximum number of smaller fishes and also lower recovery rate

Ali, M.H.

Aragon, Miguel L.

Mateo, Lun G.

Aquatic Commons

B11ngl!ldeshf Fish. Res., 10(1), 2006: 35-39 
Effect of stocking density on growth and yield of GIFT 
tilapia under rice-fish production system 
M. Hazrat Ali1'*, Lun G. Mateo and Miguel L. Aragon 
College of Agriculture, Central Luzon State University, Science City of Munoz, Nueva Ecija, Philippines 
Present Address: 1Rice Farming Systems Division, Bangladesh Rice Research Institute 
Gazipur 1701, Bangladesh 
*Corresponding author 
Abstract 
The study was conducted at the Central Experimental Station, Philippine Rice Research 
Institute, Maligaya, Science City of Munoz, Nueva Ecija, Philippines during the wet 
season to determine the suitable stocking density(s) for better growth and yield of fish 
under rice-fish production systems. Recovery rate of GIFT tilapia in different stocking 
densities ranged from 75.74 to 83.47%. Among different treatments, rice + 5,000 
fingerlings/ha and rice + 10,000 fingerlings/ha resulted in the highest recovery rate of 
83.33% and 83.47%, respectively. The lowest recovery rate of 75.75% was obtained from 
rice + 20,000 fingerlings/ha, but similar to that was obtained (78.56%) from rice + 15,000 
fingerlings/ha. Significantly higher rate of gain in body weight and that of specific 
grovvth rate were recorded in the treatment from rice + 5,000 fingerlings/ha, while other 
treatments resulted in similar absolute and specific growth rate. Fish yield increased 
significantly with relatively higher stocking densities, but higher densities produced 
maximum number of smaller fishes and also lower recovery rate. 
Key words: Rice-fish, Stocking density, Fish yield 
Introduction 
Fingerling population per unit area at stocking has great influence on marketable sizes 
and fish yield at harvest (Deng 1985). Generally, the production per unit area increases 
with the stocking in numbers and inversely the individual growth increases when the 
stocking decreases. However, stocking density depends on the size and productivity of 
the water. The more is stocked, the greater is the amount of natural food consumed 
resulting in natural food scarcity and growth stagnation. Literature also suggested that 
higher stocking with respect to number of fish result in better use of available natural 
food, hence higher production. According to Yuchang and Yixian (1992), stocking rates 
are closely related to fish yield. Therefore, to achieve the maximum fish yield, stocking 
density could be maximized considering the carrying capacity of water bodies to 
minimize the adverse effect on the growth rate of the fish. This study has been 
undertaken to determine appropriate stocking density for obtaining optimum growth, 
recovery rate and fish yield in the rice-fish culture system. 
M. Hazrat Ali er al. 
Materials and methods 
The study was conducted at the Central Experimental Station, Philippine Rice 
Research Institute, Maligaya, Science City of Munoz, Nueva Ecija, Philippines during 
the wet season. The experiment was conducted in 15 plots and the size of each plot was 
l l.6m x 10.6m. Five treatments were employed as: the treatments were: T 1 = Rice alone 
(Control), T 2= Rice + 5,000 fingerlings/ha, T 3 == Rice+· 10,000 fingerlings/ha, T 4= Rice 
+ 15,000 fingerlings/ha, T 5= Rice + 20,000 fingerlirigs/ha. Each treatment was 
replicated three times and the experimental plots were laid out in RCB design. 
Traditional method of rice cultivation was followed in the system. To provide adequate 
water for fish, dikes of each plot having the width of 50 cm at the base and 30-40 cm at 
top with the height of 40-50 cm as suggested by Sevilleja (1978). 
A pond refuge covering 10% of the land was excavated in each plot, except the 
control plot, as shelter for fish during adverse condition. In addition, plots were also 
provided with separate screen for water inlets and outlets and to protect the fish from 
escaping the plots. 
Fingerlings of GIFT (genetically improved farmed tilapia) tilapia with average body 
weight of 12.09 g were stocked in the plots as per treatments after 15-days of rice 
transplanting. The GIFT strain has been developed by combining the best performing 
genetic groups, based on their additive genetic performance from eight diverse Nile 
tilapia strains and their crosses (Eknath et al. 1993). It can survive in extremely adverse 
conditions and provided opportunity for better yield from rice-fish culture systems. The 
depth of water was maintained 11~15 cm in all the treatments throughout the growing 
period. A supplementary feed was supplied two times a day (50% at 7-8 a.m. and 
remaining 50% at 4-5 p.m.) based on 10 percent of the body weight at stocking. Feed 
supplying started 1-day after releasing of fingerlings. Fishes were harvested at 92 days 
cultured period immediately after the harvest of rice. 
Fish mortality, recovery percentage, final weight, absolute growth, absolute growth 
rate, and specific growth rate and fish yield were recorded from the harvested 
individuals. All collected data were analyzed by using analysis of variance (ANOV A) and 
means were computed by DMRT in IRRISTAT Version 3.1. 
Results and discussion 
Recovery rate. GIFT tilapia is a hardy fish that has higher survival rate. No dead 
fish was found in the rice field day after release and onwards. However, at harvest, the 
recovery rate ranged from 75.74 to 83.47%. The highest recovery was recorded at lower 
densities with 5000 and 1000 fish per ha and the lowest (75.74%) was derived from the 
highest stocking densities with 20,000 fingerlings/ha (Table 1). Kim and Kim (1992) 
found 92% survival rate of tilapia in rice field after four months of cultured period. 
Results also suggested that the contribution of big size fishes in total recovery rate 
ranged from 32.52 to 74.73% (Table 1). During the study period, sometimes heavy rain 
occurred causing the rice field overflow. As a result, some fish might have escaped from 
36 
Effect of stocking density on GIFT under rice-fish system 
the field and also some fishes hid under the mud. These factors might have made the 
variation of recovery at harvest. Nevertheless, the results suggest that lower stocking 
density produces higher recovery rate while higher stocking density produces lower 
recovery rate. 
Table 1. Mortality and recovery rate of GIFT tilapia with different stocking in rice-fish 
culture systems, wet season, Philippines 
At At harvest 
Treatments release Big size 
I 
Medium I Small 
I 
Total 
(nos.) (nos.) (nos.) (nos.) (nos.) 
Rice + 5,000 62 46.33 b 5.33 c 51.66 d 
finger lings (74.73) (8.60) 
Rice + 10,000 123 80.0 a 16 ab 6.67 102.67 b 
fingerlings (65.04) (13.01) (5.42) 
Rice + 15 ,000 185 80.67 a 31.67 b 33.0 145.33 c 
fingerlings ( 43.60) (17.12) (17.84) 
Rice + 20,000 246 80.0 a 56.33 a 50.0 186.33 a 
finger lings (32.52) (22.90) (20.33) 
CV('Yri) 8.7 33.5 3.7 
Means followed by a common letters is not significantly different at 5% level by DlviRT 
Recovery 
rate(%) 
83.33 a 
83.47 a 
78.56 b 
75.75 b 
2.8 
Figure within the parenthesis indicate the values of contribution (%) in total recovery rate in the respective 
parameters. 
Growth performance of GIFT tilapia 
Results indicated that the average final body weight gain (big, medium and small) of 
GIFT tilapia ranged from 121.10 to 89.06 g. The highest average growth (121.10 g) gain 
was obtained from rice + 5,000 fingerlings/ha while the lowest (89.06 g) was derived 
from rice + 20,000 fingerlings/ha (Table 2). Results also showed highly significant 
difference between the growth parameters obtained in the lowest stocking density (rice 
+ 5,000 fingerlings/ha) and the growth parameters recorded in the rest of the stocking 
densities. However, the mean growth obtained from the rest of the stocking densities 
(10,000-20,000 fingerling/ha) were identical (Table 2). 
Final body weight gain of individual size of fish showed that only big size fish 
produced the highly significant differences in body weight gain. The highest body 
weight (160.64g) was obtained from rice+ 5,000 fingerlings/ha and the lowest (126.18 g) 
was obtained from rice + 20,000 fingerlings/ha. 
The body weight gain of medium and small fish showed negligible variations which 
were not statistically different within their respective treatments. The results of the 
medium and small fish indicated that the body weight of these two groups of fish did not 
depend on stocking density which was observed in bigger size fish. The mean values of 
absolute growth, absolute growth rate, and specific growth rate for three groups of fish 
decrease with the increase in stocking density gave a similar trend as observed in the 
final body weight (Table 2). 
37 
M. Hazrat Ali er al. 
Table 2. Growth performance of GIFT tilapia under various stocking densities in 
rice-fish culture systems 
Initial Final Average Average 
Treatments weight weight growth growth rate 
(g) (g) (g) (g/day) 
Rice + 5,000 12.09 121.lOa 109.0la 1.18 a 
fingerlings/ha 
Rice + 10,000 12.09 94.65 b 82.56 b 0.90 b 
finger! in gs/ha 
Rice + 15,000 12.09 90.57 b 78.48 b 0.85 b 
finger lings/ha 
Rice + 20,000 12.09 89.06 b 76.97 b 0.84 b 
fingerlings/ha 
CV(%) 4.3 4.9 5.1 
Means followed by a common letter are not significantly different at 5% level by DMRT. 
Fish yield 
Specific 
growth 
rate(%) 
2.44 a 
2. 19 b 
2.13 b 
2.12 b 
1.6 
Mean fish yield of three fish sizes (big, medium and small) showed highly 
significant differences among the treatments (Fig. 1). The yields obtained from the 
treatments ranged from 639.84 to 1435.15 kg/ha with the highest fish yield (1434.15 
kg/ha) in treatment (rice+ 20,000 fingerlings/ha) and the lowest fish yield (639.84 kg/ha) 
in treatment (rice + 5,000 fingerlings/ha) as shown in Fig. 1. Kim and Kim (1992) 
obtained 2,720 Kg/ha of tilapia from rice field with four months stocking period. 
1600 Cf) l[) c.o 
Cf) ~ ~ OJ 1400 c.D ~ C\I 
C\J ~ 
1200 0 ~ 
1000 "1' I ~ 
' m OYield (l<g/ha) 800 1ffi [;]Recovery(%) 600 400 I ·.~ ·.~ I ' Cf) 
200 ! . ' OJ 
0 I 
T2 T3 T4 TS 
Treatments 
Fig. 1. Fish yield and recovery rate in the different treatments with various stocking density in 
rice-fish culture systems. 
The contribution of big, medium and small size of the fish ranged from 57.20 to 
94.54, 5.46 to 25.23 and 3.4 to 17.57%, respectively. These results suggested that the 
38 
Effect of stocking density on GIFT under rice-fish system 
contribution of bigger fish in total fish yield much more than medium and small size 
fishes. 
Principles of aquaculture suggest that higher stocking density results in higher fish 
yield. Stocking density, however, depends on the size and productivity of the water 
body. \'V'here stocking densities is higher, there is the greater amount of natural food 
consumed. This results in insufficient calories, for each individual fish offered by the 
natural food, which results in growth stagnation unless supplementary feed is given to 
the fish. In the study, however, the rice field was supplemented with fish feed (rice bran 
75 % and commercial feed, floating pellet 25%). Therefore, the feed perhaps was enough 
to optimize growth resulting in higher fish yield even if stocking density was increased. 
Based on the results of the study, it could be suggested that increase in stocking 
density reduces individual body weight. Conversely, reduced stocking results in an 
increase in individual growth of fish that takes advantage of the period during which 
growth reaches at its maximum. 
References 
Deng, Z., 1985. A new way of rural economics development, p. 159-164. In MAAHF.A selecLionor 
rice-fish farming experiences in China. Fishery Bureau, MinisLry of AgriculLUre, Animal 
Husbandry and Fishery, China. 
Eknath, A.E., M.M Tayamen, M.S Palada-De Vera, J,C. Danting, R.A. Reyes, E.E.Dioniso, J.B. 
Caplili, H.L.Bolivar, T.A. Abella, A.V. Circa, H.B.B Entsen, B. Gjerde, T. Gjedren and R.S. 
Pullin, 1993. Genetic improvement of farmed tilapia: the growth performance of eight strains 
of Orechromis niloticus tested in different farm environments. Aquaculture, 111: 171-188. 
Kim, B.M., Y.H. Kim, 1992. Rice-fish farming systems and future prospects in Korea, p. 63-67. In: 
C.R. dela Cruz, C. Lightfoot, B.A. Costa-Pierce, V.R. Carangal and M.P. Bimbao (eds.), 1992. 
Rice-fish Research and Development in Asia. International Center for Living Aquatic 
Resources Management (ICLARM). Makati, Manila, Philippines.ICLARM Conf. Proceedings 
24, 457 p. 
Sevilleja, RC., 1978. Alternative and modified management systems for rice-fish culture. Report of 
17th Asian Rice Farming System Working Group Meeting, 5-11 Oct., 1986. 
Yuchang, X. and G. Yixian, 1992. Rice-fish farming systems research in China, p. 315-323. In: 
C.R. dela Cruz, C. Lightfoot, B.A. Costa-Pierce, V.R. Carangal and M.P. Bimbao (eds.), 1992. 
Rice-fish Research and Development in Asia. International Center for Living Aquatic 
Resources Management (ICLARM). Makati, Manila, Philippines. ICLARM Conf. 
Proceedings, 24, 457 p. 
(Manuscript received 1 February 2006) 
39 


Effect of stocking density on growth and yield of GIFT tilapia under rice-fish production system

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Effect of stocking density on growth and yield of GIFT tilapia under rice-fish production system

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