LARGE SCALE FISH PRODUCTION THOUGH CARP POLYCULTURE SYSTEM IN A FISH FARM IN BANGLADESH
Authors:
1.
Jagannath University
Type:
Article
Pages:
from 67
to 73
Status:
Published
Received:
05.12.2016
Accepted:
25.12.2016
Published:
25.12.2016
Subject area:
UDK 639.371.5.03/.06:639.3(549.3)
GRNTI 34.39 Физиология человека и животных
GRNTI 62.13 Биотехнологические процессы и аппараты
GRNTI 69.01 Общие вопросы рыбного хозяйства
GRNTI 69.25 Аквакультура. Рыбоводство
GRNTI 69.31 Промышленное рыболовство
GRNTI 69.51 Технология переработки сырья водного происхождения
GRNTI 87.19 Загрязнение и охрана вод суши, морей и океанов
GRNTI 34.39 Физиология человека и животных
GRNTI 62.13 Биотехнологические процессы и аппараты
GRNTI 69.01 Общие вопросы рыбного хозяйства
GRNTI 69.25 Аквакультура. Рыбоводство
GRNTI 69.31 Промышленное рыболовство
GRNTI 69.51 Технология переработки сырья водного происхождения
GRNTI 87.19 Загрязнение и охрана вод суши, морей и океанов
Language:
Russian
Keywords:
pond, polyculture, carp, growth rate, production volume
Abstract (English):
The aim of the study is to obtain maximum fish production per unit area within semi-intensive culture system. The duration of rearing Rui ( Labeo rohita ), Catla ( Catla catla ), Mrigal ( Cirrhinus mrigala ), Common carp ( Cyprinus carpio ), Grass carp ( Ctenopharyngodon idella ) and Silver carp ( Hypophthalmichthys molitrix) in 5 ponds (0.15 ha to 0.18 ha in size and water depth 2-2.5 m) was 8 months (March-October). All the aquatic vegetation was removed, all unwanted fish were destroyed with phostoxin. In 7 days after liming (200 kg/ha) the following fertilizers were introduced: organic (coudung at the rate of 1500 kg/ha) and chemical (urea - 50 kg/ha, TSP - 25 kg/ha). The water temperature was 28.4 ± 0.18 to 29.2 ± 0.88, pH value ranged from 6.96 ± 0.34 to 7.43 ± 0.52 and dissolved oxygen was 6.72 ± 0.22 to 7.74 ± 0.55 mg/l. In addition, fingerlings got fish flour, rice bran, wheat bran, mastered oil cake (once a day according to 4-6 % of the body weight). Sampling of fish was every 15 days. The highest average level of survival of fish was 89.2% (Rui - 91.0%), the lowest - 82.9% (carp - 78.0%). The average maximum weight was fixed in silver carp - 814.2 ± 11.8 and grass carp - 781,1 ± 11,8; the average minimum was in Rui (501.6 ± 10.8). The total volume of fish production (25 877.78 kg/ha) was higher than the average fish culture procedures followed in the rural areas of Bangladesh. Rui (1254.11 kg/ha, pond area 0.18 ha) and Mrigal (1222.22 kg/ha, pond area 0.15 ha) dominated by this parameter despite the highest values of stocking density. The obtained results confirm the efficiency of the proposed method of fish production in polyculture.
The aim of the study is to obtain maximum fish production per unit area within semi-intensive culture system. The duration of rearing Rui ( Labeo rohita ), Catla ( Catla catla ), Mrigal ( Cirrhinus mrigala ), Common carp ( Cyprinus carpio ), Grass carp ( Ctenopharyngodon idella ) and Silver carp ( Hypophthalmichthys molitrix) in 5 ponds (0.15 ha to 0.18 ha in size and water depth 2-2.5 m) was 8 months (March-October). All the aquatic vegetation was removed, all unwanted fish were destroyed with phostoxin. In 7 days after liming (200 kg/ha) the following fertilizers were introduced: organic (coudung at the rate of 1500 kg/ha) and chemical (urea - 50 kg/ha, TSP - 25 kg/ha). The water temperature was 28.4 ± 0.18 to 29.2 ± 0.88, pH value ranged from 6.96 ± 0.34 to 7.43 ± 0.52 and dissolved oxygen was 6.72 ± 0.22 to 7.74 ± 0.55 mg/l. In addition, fingerlings got fish flour, rice bran, wheat bran, mastered oil cake (once a day according to 4-6 % of the body weight). Sampling of fish was every 15 days. The highest average level of survival of fish was 89.2% (Rui - 91.0%), the lowest - 82.9% (carp - 78.0%). The average maximum weight was fixed in silver carp - 814.2 ± 11.8 and grass carp - 781,1 ± 11,8; the average minimum was in Rui (501.6 ± 10.8). The total volume of fish production (25 877.78 kg/ha) was higher than the average fish culture procedures followed in the rural areas of Bangladesh. Rui (1254.11 kg/ha, pond area 0.18 ha) and Mrigal (1222.22 kg/ha, pond area 0.15 ha) dominated by this parameter despite the highest values of stocking density. The obtained results confirm the efficiency of the proposed method of fish production in polyculture.
Keywords:
pond, polyculture, carp, growth rate, production volume
pond, polyculture, carp, growth rate, production volume
Introduction Bangladesh is a densely populated country of 147 570 km2 with a population of 130 million people. It is fortunate in having an extensive water resource in the form of ponds, natural depressions (haors and heels), lakes, canals, rivers and estuaries covering an area of 4.56 million ha [1]. Bangladesh is one of the world leading inland fisheries producer with a production of 1 646 819 tonnes during 2003-2004, with marine catch total of 455 601 tonnes and a total production from aquaculture of 914 752 tonnes during 2003-2004. Bangladesh's total fish production for the year totaled above 2.1 million tonnes [1]. Food and Agriculture Organization of the United Nations (FAO) [2] ranked Bangladesh as sixth largest aquaculture producing country with its estimated production of 856 956 tonnes in 2003 [2]. Aquaculture accounted for about 43.5% of the total fish production during 2003-2004, with inland open water fisheries contributed 34.8% [1]. Polyculture, the rearing of two or more species in each culture unit, enjoys wide popularity throughout much of the world [3]. Polyculture comprises different compatible species of fish of different trophic and spatial niches are raised together in the same pond to utilize all sorts of natural food available in the pond. In Bangladesh, aquaculture production systems are mainly extensive and extended extensive, with some semi-intensive and in very few cases intensive systems. Although the culture fishery contributes over 55% of inland fish production, it covers only about 1l% of the total inland water resources. As most of the farmers are poor and living in rural area, it is not possible for them to follow the intensive technology of fish production which requires higher inputs supply. An appropriate intermediate technology for the farmers of Bangladesh, thus should be the semi-intensive culture technique which requires moderate inputs and production management based mainly on proper stocking rate and ratio and adequate manuring on a regular basis with or without supplementary feeding. Indigenous freshwater carps (22%) and exotic carps (10%) from both the farming and capture sectors are the primary contributors to total production [4]; other freshwater fish include catfish, snakeheads and small indigenous species. However, carp polyculture in ponds is more productive, capital intensive and is a more profitable activity when compared to the other culture systems. Materials and Methods The experiment was carried out in five different ponds at Ratan Matsya Khamar, Netrakona, Bangladesh. Management of fish polycuture in ponds includes successive stages from pond preparation to final harvesting of fish. Pond preparation. A pond with suitable environmental features would give higher fish production per unit area than that of a pond having adverse environmental conditions. All the aquatic vegetation (floating, submerged or emergent) was removed from the pond. The pond bottom was made even to allow effective netting and harvesting of fish. The broken pond dyke repaired. All the predatory and unwanted fishes were eradicated from the pond by using phostoxin (2 tablets/decimal). Liming of the pond was carried out at the rate of 200 kg/ha in order to neutralize the soil acidity, settles excess dissolved organic matter and make the pond free from any parasites. After 7 days of liming, ponds were manured with coudung at the rate of 1500 kg/ha. The chemical fertilizers such as urea and TSP were applied at the rate of 50 and 25 kg/ha correspondingly all over the ponds. Species selection. Selection of compatible fast growing species was of vital importance in maximizing fish production. This was also considered that the species grows fast with accumulation of natural food. A combination of six species, viz. Rui (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus mrigala), Common carp (Cyprinus carpio), Grass carp (Ctenopharyngodon idella) and Silver carp (Hypophthalmichthys molitrix). Of these, Rui was column feeder; Catla was surface feeder; Common carp and Mrigal was bottom feeder; Grass carp was surface/column feeder and Silver carp was surface feeder. Stocking density. Fishes were stocked in three tanks (Pond 1 - T1, Pond 2 - T2, Pond 3 - T3, Pond 4 - T4, Pond 5 - T5) by completely randomized design (CRD) (Table 1). Table 1 Stocking densities of different fishes in five different ponds Fish Species Stoking densities of different fish species in five different treatments T1 T2 T3 T4 T5 Rui 500 400 400 400 500 Catla 300 200 200 200 300 Mrigal 250 250 400 300 300 Common Carp 200 200 300 300 200 Grass Carp 200 150 200 200 200 Silver Carp 300 200 200 200 300 Total 1750 1400 1700 1600 1800 Pond area, ha 0.18 0.16 0.15 0.16 0.18 Supplementary feeding. After stocking of fingerlings, supplementary food (fish meal, rice bran, wheat bran, mastered oil cake and wheat flour) was applied once a day according to the 4-6% of the body weight (Table 2). Table 2 Composition of supplementary feed with theirdry weight and percentage Feed Ingredients Dry weight, g % Wheat Bran 150 15 Rice bran 250 25 Mastered oil cake 300 30 Fish Meal 200 20 Wheat flour 100 10 Sampling of fish. Sampling of fish was done in every fifteen days to check the health condition, growth rate and mortality of the fishes. Periodic sampling of fish was done at least in a month. Water quality parameters. Physical and chemical parameters such as water temperature (˚C), dissolved oxygen (mg/l), and pH were measured by thermometer, DO meter (DO8401) and pH meter (PH 004) respectively. Harvesting. Final harvesting of fish was done after 6 month of stocking in tanks when the carrying capacity of tank was saturated. Statistical analysis. Simple arithmetical tools like average, range, percentage etc. were used to tabulate the results. For analysis of treatment effects of fish production and separation of treatment means by Duncans Multiple Range Test (DMRT) were performed as per methods outlined in [5]. Results Physical and chemical parameters: The optimum fish production depends on the physical and chemical qualities of water. The water quality parameters that were recorded during the study period are provided in Table 3. Table 3 Average physico chemical parameters in five different ponds Treatments No of Estimation Physical and chemical parameters Temperature, °C pH Dissolved Oxygen, mg/l T1 32 28.4 ± 0.18 6.96 ± 0.34 6.92 ± 0.52 T2 32 29.2 ± 0.88 7.25 ± 0.38 7.35 ± 0.31 T3 32 28.8 ± 0.85 7.33 ± 0.41 7.74 ± 0.55 T4 32 28.6 ± 0.65 7.35 ± 0.31 6.85 ± 0.72 T5 32 28.7 ± 0.25 7.43 ± 0.52 6.72 ± 0.22 The values of water quality parameters were within the acceptable ranges that regulate this semi-intensive culture system strongly. The water temperature was almost the same ranged from 28.4 ± 0.18 to 29.2 ± 0.88, pH value ranged from 6.96 ± 0.34 to 7.43 ± 0.52 and Dissolved Oxygen was 6.72 ± 0.22 to 7.74 ± 0.55 mg/l. Fish Survival: During the period of investigation the survival of the fish was fairly high in all the ponds. The survival rate was estimated after the total count of the fishes at the end of the culture period. Highest survival rate was recorded in Pond 1. The survival rate of the fishes that stocked in different ponds is presented in Table 4. Table 4 Survival rate of fishes in five different ponds Treatments Species Name Stocking No. Harvested No. Survival, % T1 Rui 500 455 91.0 Catla 300 260 86.6 Mrigal 250 220 88.0 Common Carp 200 175 86.0 Grass Carp 200 181 90.5 Silver Carp 300 270 90.0 Total 1750 1561 89.2 T2 Rui 400 341 85.2 Catla 200 165 82.5 Mrigal 250 213 85.2 Common Carp 200 156 78.0 Grass Carp 150 123 82.0 Silver Carp 200 165 82.5 Total 1400 1163 83.0 T3 Rui 400 320 80.0 Catla 200 157 78.5 Mrigal 400 359 89.7 Common Carp 300 245 81.6 Grass Carp 200 166 83.0 Silver Carp 200 163 81.5 Total 1700 1410 82.9 T4 Rui 400 343 85.7 Catla 200 173 86.5 Mrigal 300 241 80.3 Common Carp 300 270 90.0 Grass Carp 200 175 87.5 Silver Carp 200 171 85.5 Total 1600 1373 85.8 T5 Rui 500 440 88.0 Catla 300 269 89.6 Mrigal 300 257 85.6 Common Carp 200 169 84.5 Grass Carp 200 173 86.5 Silver Carp 300 251 83.6 Total 1800 1559 86.6 Fish growth and production: Observations were made on fish growth performances in terms of monthly weight gain and daily weight gain. The average cumulative weight gain of fishes for five ponds is presented in Table 5. Gross production of individual species of fish was calculated from the average final weight gain multiplied by the actual number of fish harvested. Estimation for the gross fish production in different ponds is shown in Table 6. Table 5 Average cumulative growth performances in months in five different treatments Species Treat-ments Stocking Size in March, g Average cumulative growth performances, g April May June July August September October Rui T1 18.4 ± 1.1 48.4 ± 2.9 114.0 ± 3.6 161.6 ± 3.3 223.8 ± 4.8 295.3 ± 7.3 380.8 ± 5.2 464.5 ± 7.9 T2 20.1 ± 1.4 50.7 ± 3.9 111.0 ± 8.3 160.2 ± 7.6 225 ± 10.4 301.2 ± 10.9 384.6 ± 10.3 493.5 ± 13 T3 20.7 ± 0.8 60.2 ± 7.0 113.0 ± 9.3 165.2 ± 8.5 230.5 ± 11 305 ± 11.6 384.6 ± 10.3 495.9 ± 12 T4 25.0 ± 3.9 68.7 ± 9.3 121.3 ± 9.2 183.7 ± 11.6 245.3 ± 10.6 310 ± 10.3 389.1 ± 10.6 501.6 ± 10.8 T5 24.1 ± 3.0 68.2 ± 8.8 120.3 ± 7.2 182.4 ± 9.5 242.3 ± 10.2 306.8 ± 8.8 388.1 ± 8.7 500.0 ± 9.7 Catla T1 24.0 ± 3.0 88.8 ± 5.8 170.1 ± 3.3 249.7 ± 5.7 327.8 ± 6.7 413.8 ± 9.1 495.4 ± 6.4 576.8 ± 7.4 T2 25.0 ± 2.0 90.3 ± 4.3 176.5 ± 6.7 256.4 ± 6.8 334.7 ± 6.9 419.1 ± 5.7 500.5 ± 8.12 578.5 ± 9.0 T3 25.0 ± 2.0 88.5 ± 5.9 174.5 ± 8.5 254.7 ± 6.7 335.4 ± 7.4 421.0 ± 5.1 502.7 ± 10.9 582.4 ± 12.5 T4 27.5 ± 3.9 91.4 ± 10.1 180.5 ±9.0 259.2 ± 7.3 337.1 ± 9.3 425.5 ± 7.1 503.4 ± 10.6 586.1 ± 11.4 T5 28.8 ± 3.7 95.7 ± 9.1 187.4 ±8.5 264.2 ± 7.9 346.5 ± 11.5 430.5 ± 10.1 516.2 ± 9.5 601.4 ± 10.5 Mrigal T1 19.1 ± 1.6 57.0 ± 5.6 128.1 ±5.3 206.8 ± 5.9 272.1 ± 5.4 360.7 ± 4.5 457.0 ± 6.8 515.4 ± 6.0 T2 22.8 ± 1.6 75.2 ± 5.1 131.0 ±5.6 210.8 ± 7.6 278.1 ± 8.5 363.7 ± 10.3 455.5 ± 8.1 521.1 ± 9.9 T3 21.8 ± 1.3 72.2 ± 5.5 130.7 ±5.8 212.2 ± 10.1 282.7 ± 11.0 366.0 ± 9.0 458.0 ± 8.2 524.0 ± 10.7 T4 22.5 ± 1.9 74.5 ± 6.2 134.5 ± 9.3 215.2 ± 9.3 285.5 ± 11.3 371.7 ± 11.0 463.7 ± 8.6 526.8 ± 11.7 T5 26.8 ± 3.2 81.0 ± 6.1 136.5 ± 9.2 219.5 ± 7.8 288.4 ± 9.7 384.7 ± 10.7 468.0 ± 8.0 537.5 ± 10.6 Common Carp T1 22.4 ± 1.9 103.4 ± 6.1 182.0 ± 9.3 278.0 ± 13.0 345.8 ± 8.7 416.8 ± 8.7 514.8 ± 8.1 613.0 ± 12.7 T2 21.8 ± 2.4 106.0 ± 8.6 183.0 ± 8.9 279.1 ± 11.1 347.2 ± 8.4 417.8 ± 8.6 516.2 ± 7.6 618.7 ± 14.7 T3 23.0 ± 2.1 107.4 ± 7.9 182.2 ± 9.8 280.5 ± 10.0 345.7 ± 11.4 419.2 ± 10.6 515.2 ± 9.9 618.7 ± 10.5 T4 23.2 ± 2.6 108.8 ± 8.8 182.8 ± 10.0 280.1 ± 9.2 351.4 ± 9.1 425.0 ± 10.4 517.4 ± 10.4 620.1 ± 10.1 T5 24.1 ± 2.1 110.2 ± 8.9 184.0 ± 10.0 283.0 ± 10.0 362.1 ± 11.5 429.2 ± 11.4 521.7 ± 9.8 621.4 ± 10.8 Grass Carp T1 24.7 ± 1.9 111.5 ± 6.8 265.4 ±12.7 342.7 ± 10.3 467.4 ± 8.1 571.0 ± 9.4 676.0 ± 12.1 781.1 ± 11.8 T2 23.4 ± 2.0 114.5 ± 9.2 267.0 ± 11.3 344.2 ± 11.8 470.2 ± 8.5 572.1 ± 9.7 675.5 ± 11.6 774.4 ± 10.8 T3 24.2 ± 1.3 112.1 ± 8.2 265.5 ± 9.5 342.8 ± 10.0 467.0 ± 8.7 571.5 ± 10.5 672.7 ± 9.8 775.8 ± 11.1 T4 25.0 ± 2.1 114.0 ± 8.3 266.7 ± 9.2 345.2 ± 11.4 469.5 ± 9.05 576.4 ± 9.2 673.2 ± 8.7 775.1 ± 10.5 T5 26.1 ± 2.4 115.0 ± 8.5 265.7 ± 11.4 344.1 ± 10.0 466.7 ± 8.2 574.8 ± 8.0 670.0 ± 7.9 773.0 ± 9.7 Silver Carp T1 32.0 ± 2.7 132.5 ± 5.8 284.4 ± 7.1 375.0 ± 7.6 492.1 ± 10.0 604.8 ± 14.2 715.0 ± 12.2 810.0 ± 14.5 T2 33.0 ± 2.3 138.4 ± 6.1 280.0 ± 8.2 379.2 ± 7.9 502.1 ± 15.8 613.4 ± 13.6 720.4 ± 13.8 814.2 ± 11.8 T3 32.0 ± 1.9 139.7 ± 8.2 279.0 ± 8.8 382.8 ± 11.9 513.2 ± 11.7 616.4 ± 12.1 722.0 ± 10.7 812.8 ± 10.0 T4 32.8 ± 2.1 141.1 ± 9.1 285.2 ± 9.7 386.8 ± 11.3 517.5 ± 9.3 620.5 ± 9.5 723.5 ± 10.3 814.2 ± 10.6 T5 31.2 ± 1.8 136.8 ± 9.1 272.7 ± 9.2 375.7 ± 10.5 499.7 ± 10.5 607.8 ± 9.7 704.4 ± 9.6 795.0 ± 11.9 Table 6 Gross production of fishes in five different treatments Species Name Treatments Fish stocking No. No. of Survival Initial weight, g Final weight, g Gross Production, kg Area of pond, ha Gross production, kg/ha/crop Rui T1 500 455 18.4 464.5 211.35 0.18 1174.15 T2 400 341 20.1 493.5 168.28 0.16 1051.77 T3 400 320 20.7 495.9 158.69 0.15 1057.92 T4 400 343 25.0 501.6 172.05 0.16 1075.31 T5 500 440 24.1 500.0 220.00 0.18 1222.22 Catla T1 300 260 24.0 576.8 149.97 0.18 833.16 T2 200 165 25.0 578.5 95.45 0.16 596.58 T3 200 157 25.0 582.1 91.39 0.15 609.26 T4 200 173 27.5 586.1 101.40 0.16 633.72 T5 300 269 28.8 601.4 161.78 0.18 898.76 Mrigal T1 250 220 19.1 515.4 113.39 0.18 629.93 T2 250 213 22.8 521.1 110.99 0.16 693.71 T3 400 359 21.8 524.0 188.12 0.15 1254.11 T4 300 241 22.5 526.8 126.96 0.16 793.49 T5 300 257 26.8 537.5 138.14 0.18 767.43 Continued table 6 Gross production of fishes in five different treatments Species Name Treatments Fish stocking No. No. of Survival Initial weight, g Final weight, g Gross Production, kg Area of pond, ha Gross production, kg/ha/crop Common Carp T1 200 175 22.4 613.0 107.28 0.18 595.97 T2 200 156 21.8 618.7 96.52 0.16 603.23 T3 300 245 23.0 618.7 151.58 0.15 1010.54 T4 300 270 23.2 620.1 167.43 0.16 1046.42 T5 200 169 24.1 621.4 105.02 0.18 583.43 Grass Carp T1 200 181 24.7 781.1 141.38 0.18 785.44 T2 150 123 23.4 774.4 95.25 0.16 595.32 T3 200 166 24.2 775.8 128.78 0.15 858.55 T4 200 175 25.0 775.1 135.64 0.16 847.77 T5 200 173 26.1 773.0 133.73 0.18 742.94 Silver Carp T1 300 270 32.0 810.0 218.70 0.18 1215.00 T2 200 165 33.0 814.2 134.34 0.16 839.64 T3 200 163 32.0 812.8 132.49 0.15 883.24 T4 200 171 32.8 814.2 139.23 0.16 870.18 T5 300 251 31.2 795.0 199.55 0.18 1108.58 Total 25877.78 Due to availability of the supplementary food the fishes are increased in body weight enormously. All of six species attained an average maximum weight at the last month of the study period (Table 5) in five different ponds. Silver carp attained the maximum weight 810.0 ± 14.5, 814.2 ± 11.8, 812.8 ± 10.0, 814.2 ± 10.6 and 795.0 ± 11.9 g in five ponds respectively. Grass carp also followed by the silver carp that gained their weight 781.1 ± 11.8, 774.4 ± 10.8, 775.8 ± 11.1, 775.1 ± 10.5 and 773. 0 ± 9.7 g in Pond 1, Pond 2, Pond 3, Pond 4 and Pond 5 respectively. Rui gained their maximum weight (501.6 ± 10.8) in Pond 4. Catla, Mrigal and Common Carp gained their maximum weight 601.4 ± 10.5, 537.5 ± 10.6 and 621.4 ± 10.8 g respectively in the same pond (Pond 5). This also noted that in the Pond 5 silver carp comparatively gained minimum weight where Catla gained their maximum weight. Discussion The average growth of Rui (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus mrigala), Common carp (Cyprinus carpio), Grass carp (Ctenopharyngodon idella) and Silver carp (Hypophthalmichthys molitrix) were observed in all five ponds. The average cumulative growth increment of fishes showed that fishes gained their weight significantly with the months. In this semi-intensive pond culture system, due to availability of natural food the fishes were fed actively and gained their weight very quickly. Davis et al. [6] observed that slow growth of fishes due to less feeding activity during fish growth study. Observations made on the five ponds clearly indicate that silver carp exhibited better growth than other species. But the growth rate of grass carp also followed by the silver carp and the growth rate of common carp is closer to the grass carp. This indicates that the growth rate of the exotic carps is higher than any other fish species. Jhingran [7] reported about the superiority of growth performances by silver carp. In the water quality parameter, the recorded water temperature (28.4 ± 0.18 to 29.2 ± 0.88) was favorable for active growth and feeding of fishes because water temperature affects the feeding pattern and growth of fish. The range of pH and dissolved oxygen was also in normal condition that affected the growth of the fishes positively. From the investigation, it is found that the production of fish is high and rather satisfactory. DoF [8] reported that Carp production from trial and experimental ponds was 2000 kg/ha/yr. Conclusion Polyculture is an effective way to maximize benefit from available natural food in a pond. The possibilities of increasing fish production per unit area, through polyculture, are considerable. Growth rate of these carps in semi intensive culture system was higher than we observed. The productivity, growth and survivability of the fishes in the pond environment were notable. The present study disclosed that the production of the ponds was higher than the average fish culture procedures followed in the rural areas of Bangladesh. This indicates that the feed and fertilizers used were adjusted according to the body weight.
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