Proceedings of the UNESCO - University of Tsukuba International Seminar on Traditional Technology for Environmental Conservation and Sustainable Development in the Asian-Pacific Region, held in Tsukuba Science City, Japan, 11-14 December, 1995.
Editors: Kozo Ishizuka, D. Sc. , Shigeru Hisajima, D. Sc. , Darryl R.J. Macer, Ph.D.
and Mr. M.G.M. Alam
Research Student, Tsukuba University, Japan
Production from inland open water capture fisheries is being depleted due to over-exploitation and habitat degradation. However, aquaculture production both from fresh water and brackish water which mostly follows traditional and improved traditional practices has been steadily increasing. Semi-intensive shrimp farming in a limited scale is a recent development where production of 3-5 ton/ha is being obtained. Production from improved traditional practices which comprises over 95% of the total shrimp farming is as low as 300-500 kg/ha. Aquaculture technologies so far developed and practiced in Bangladesh include polyculture of carps, integrated aquaculture, culture of tilapia and silver barb in seasonal water bodies, breeding and culture of various catfishes, culture of fish in pens, brood stock improvement and nursery management etc. These are very low input environment friendly sustainable technologies being able to produce 2-6 ton/ha or more depending on the management and culture practices with assurance of good quality produce.
Key Words: Aquaculture technology, Sustainable development, Fish, Shrimp.
In the agro-based economy of Bangladesh, fish and fisheries play an important role in nutrition, income, employment and foreign exchange earnings. It contributes 73% to national animal protein intake, 4% to GDP and 10% to export earnings, in addition to providing full time employment to 1.4 m people and part time employment to another 11 m. An estimated 73% of rural households are involved in rural fishing.
The production of fish in 1993-94 has been estimated to be about 1.08 m tons. Inland open water capture fisheries contributes to 51%, inland fresh and brackish water aquaculture 25% and marine capture fisheries 24%. Current per capita fish consumption is about 25.0 g up from 20.5 g in 1989-90. However, to achieve recommended consumption rate of 38 g/capita/day, the country needs to produce about 1.9 m tons of fish. Vast potential exists to achieve this production through sustainable development of aquaculture and resource management. The role of fisheries in nutrition and economy of Bangladesh is shown in Table 1.
During 1994-95, export earnings from fish and fishery products increased considerably to Tk. 13,000 m (US$ 325 m; Tk. 40=US$ 1) in foreign exchange of which the export of shrimp alone contributed to Tk. 10,400 m (US$ 260 m) (DOF, 1994). The production of shrimp in 1992-93 from the sea was 23,233 tons, from rivers and inland water bodies 53,520 tons and from coastal shrimp farms about 23,530 tons, the country total being 101,025 tons (Hussain and Uddin, 1995).
Fisheries contribute: : 4.0% of GDP
Source Water area Production % contribution to
Culture of tilapia
FRI then in 1987 and 1988 imported black and red tilapia, carried out investigation on their biology and behaviour and successfully developed culture technologies through research. As a short-cycled quick growing fish, O. niloticus has proved as a worthy fish for culture in seasonal ponds and ditches in the rural areas of the country which retain water for 4-6 months. The culture technology is so simple that by stocking at a density of 20,000/ha and by using 60% rice bran and 40% mustard oil cake as feed, a production of 3.5 tons/ha was possible to obtain in 6 months with a net profit of Tk. 65,000. Under intensive system, net yield of 6.6 tons/ha/6 months was obtained in monosex culture which makes aquaculture of tilapia competitive than any other trade.
In case of red tilapia, a production of over 5.5 tons/ha/yr was achieved applying the same management practices. In such culture practices the fish farmers could get a net profit of Tk. 0.19 m/ha/yr. This low-input technology is suitable for rural women's participation in the context of socio-religious point of view where women can not get out of home for work. Culture of tilapia even in seasonal ponds and ditches would substantially increase the country's total production of fish.
Culture of Silver barb (Puntius gonionotus
Figure 1: Map of Bangladesh
Taking into account of the potential and prospect of tilapia and silver barb culture in large number of country's existing seasonal ponds and ditches, the successful transfer of the technology to the farmers would certainly bring a revolutionary change in aquaculture production, public nutrition and economy of Bangladesh.
Polyculture of carps
In case of medium and large farmers who have some financial resources, integration of polyculture with poultry has been found to be highly profitable. It is evident that through aquaculture practice, a farmer can increase his income 5-7 times more than from agriculture, thus offering an excellent opportunities for generation of employment and alleviation of poverty.
Integrated poultry/duck fish farming
In integrated poultry/duck fish farming, droppings of birds and feed wastes are recycled in ponds for production of fish. Only by raising 500 ducks or chickens in a poultry shed over per hectare pond, production of 4.0-6.0 tons/ha/yr of fish in the case of duck-fish and 4.0 tons/ha/yr in the case of chicken-fish was obtained. In addition, up to 240 eggs were obtained per bird per year (Latif et al., 1993). Broiler/fish is more profitable than layer/ fish farming as the broilers grow fast and become sellable within 6-8 weeks thus ensuring quick cash return for the poor farmers. Use of 500 birds/ha has been found a standard density which keeps water quality good for domestic purposes except for drinking. Here, except feeding the birds, the fish do not require any supplementary feed or fertilizer in order to grow.
In such an integrated system, poultry excreta acts as manure in the pond and enter into the food-chain in the pond ecosystem. Economic analysis of operations proved the system to be highly remunerative providing a net profit of up to Tk. 0.16-0.18 m/ha/yr thereby enhancing productivity of land many-folds.
In the context of present rice cultivation method, two crops of paddy (long-stem transplanted Aman in Kharif and HYV in Rabi season) and a single crop of fish rearing through both the seasons can be obtained. In Bangladesh, short-cycled fish like, Silver barb (P. gonionotus ), Tilapia (O. niloticus ), Common carp (C. carpio ) and shrimp (M. rosenbergii ) in freshwater paddy fields, P. monodon in coastal paddy fields have been found to grow well in rice-fields.
In rice-fish farming experiments of FRI, production of T. Aman ranged from 0.6-3.0 tons/ha and that of second crop of boro ranged from 4.5-5.0 tons/ha. Production of fish (major carps, common carp and silver barb) stocked at a density of 6,000-9,000/ha ranged from 0.70-0.80 tons/ha. Net benefit from concurrent rice-fish culture would stand around Tk. 41,208.0/ha/6 months. Freshwater giant prawn (M. rosenbergii ) when cultured with rice at 16,000-17,000 stocking density/ha, produced 0.30-0.40 tons/ha (Haroon, 1989). Both fish and shrimp culture with rice do not require any feed or any extra fertilizer other than those that are normally applied for rice.
In rice-fish integration as shown in Figure 2, crop residues (brans and straw) can be used as feed to fish (bran) and livestock (bran and straw); pond mud can be used as manure in rice fields and vegetable plots and livestock manure can be used for fertilizing fish ponds and rice fields.
Coastal saline soils occupy an estimated 2.8 m ha in southern part of the country which receive tidal saline water and hold for few months. Kharif paddy varieties are widely cultivated in these areas. After the tidal water enters in March, tiger shrimp (P. monodon ) and mullet (Liza parsia ) are stocked at a density of 100,000/ha and cultured up to June and harvested. Subsequently, saline water is drained off before monsoon and after washing out the land with monsoon water, kharif paddy cultivation with freshwater fish is undertaken. The fish cultivation for 3 months gives an yield of 0.25-0.30 tons/ha of which 40% is contributed by M. rosenbergii and the rest by carps.
In Bangladesh, both native and exotic catfishes are popular to the farmers. Among them Ompok pabda , Mystus cavasius , Clarias batrachus , Pangasius pangasius are native and C. gariepinus and P. sutchi are exotic. Breeding and culture techniques of all of them have been developed.
Hybrids have been produced through cross breeding between native female C. batrachus and male African C. gariepinus . The F1 hybrid showed better growth and survival than the parental stocks and proved to be a maternal heterosis. This hybrids attain a size of 200-300 g within 2-3 months, where it needs about one year for C. batrachus to grow to this size. Fingerlings of 5-10 g in size are stocked at a density of 50,000 - 400,000/ha depending on the culture and management practices. Feeding is applied daily at 4-5% of body weight. Formulated diet containing either fish meal (40%), rice bran (20%), wheat bran (15%), oil cake (20%), molasses (4%) and vit. premix (1%) or fish meal (2%), blood meal (22.5%), sesame oil cake (23%), rice bran (43.5%), flour (4.5%), vit. premix (0.5%), salt (1%), soybean oil (1%) and oyster shell (2%) is used as feed. Fish production ranges between 49.0 and 50.0 tons/ha and net profit is around Tk. 1.70 m/ha.
Polyculture of Pangasius spp. with major carps at a stocking density of Pangasius 8,000/ha, Catla 1,000/ha and Labeo 500/ha produced an yield of 4.0-4.5 tons/ha/yr and net benefit was at the tune of Tk. 0.194 m/ha/yr. In contrast, monoculture of Pangasius produced only 2.0-2.5 tons/ha/yr. In 1990, P. sutchi was introduced to Bangladesh from Thailand. Subsequently its breeding and larval rearing techniques have been developed in 1993. By now it became one of the popular species for closed water aquaculture.
Culture of fish in pens
Genetic approaches to the stock improvement of some commercially important fishes
Improvement of stocks of P. gonionotus , C. catla and L. rohita through selective breeding and line crossing techniques is in progress.
Fish feeding and nutrition
Initially a nationwide survey was undertaken to identify potential fish feed ingredients based on their availability, price and primary nutritional value (FRI, 1989). Eighty three different types of ingredients, both of plant and animal origin, have been studied. The survey covered materials that are being traditionally used and also non-conventional items such as, kitchen waste, processed waste from the food/fish industry, aquatic weed, etc. On the basis of the results, 35 out of 83 ingredients were found suitable as fish feed. Most important ones are : rice bran, wheat bran, mustard oil cake, sesame oil cake, fish meal, animal blood meal and viscera, silk worm pupae and aquatic plants like, water hyacinth, duck weed, azolla, etc.
The use of animal protein source in the supplemental feed is most important for growth. The institute from an investigation determined that the requirement of protein in the diet for various species of major carps remain between 35% and 45% depending on the type of species (Akhter et al, 1993). Keeping in view the socio-economic aspects of rural poor fish farmers, the Institute has developed low-cost but high quality supplementary feed for carp polyculture and nursery. The formula of two such supplementary feed are given in Table 4.
Ingredients % used % protein
Aquaculture for its high potential is expanding at a faster rate because of development of improved technology. However, the shortage of fish seed is a major constraint. This problem can be reduced to an extent if the hatchlings produced in the hatchery are raised properly in nursery pond. To meet the increased demand for fish seed for large-scale aquaculture extension, the Institute conducted a series of experiments for the development of nursery technique to increase the growth and survival through improved pond preparation and optimizing stocking density, feeding and fertilization. A flow diagram of improved nursery management operation of carp is in Figure 3.
Improved nursery management practice follows a double stage rearing technique. In the first stage nursery, fries are stocked at a density as high as 8.0 m/ha and reared for up to 21 days to attain 2.5 cm size survival rate being obtained as 70%. In the second stage nursery, stocking density is reduced to 10% (0.8 m/ha) and reared for 60 days to get fingerlings of 5.0-7.5 cm size which are suitable for stocking in the ponds (Haque et al, 1993, 1994). The net income derived from nursery operation of a 10 decimal pond was estimated to be Tk. 0.16-0.19 m.
From economic point of view, shrimp is a high value commodity in the world market. In Bangladesh, a large quantum of foreign exchange earnings (9% of total export earnings) is being generated from the export of both freshwater and marine shrimps and is continuously increasing year by year. This has given a big push in rapid expansion of brackish water shrimp farming in the coastal areas. However, freshwater shrimp farming did not progress significantly compared to the brackish water shrimp culture, although favourable climatic conditions prevail.
Freshwater giant prawn (M. rosenbergii ) is the major freshwater shrimp in respect of production and demand. Keeping this in view, FRI gave a major thrust for the development of a viable technology for commercial culture of Macrobrachium in freshwater ponds and achieved significant success. Monoculture of Macrobrachium at a density of 15,000/ha yields 0.277-0.322 tons/ha/6 months (Mahmud et al, 1991, 1993) which is quite satisfactory compared to the present level of production of 0.15-0.20 tons/ha from extensive culture practice.
Polyculture of Macrobrachium with fish is more profitable than its monoculture. A production of 3.0 tons/ha of fish and 0.20 tons/ha of prawn is obtained when juveniles of shrimp are stocked at a density of 10,000/ha and fish at 5,000/ha (following recommended ratios for various carp species) and cultured for 8-10 months in perennial waters. Macrobrachium has also been found suitable for concurrent culture with rice and a production of about 0.30-0.40 tons/ha/6 months is obtained in such operation.
Macrobrachium constitutes about 70% of the total freshwater prawn production. So, culture of Macrobrachium in ponds with fish would not only increase total pond production but would also raise the economic return of the farmer in view of the high price it commands in the market. However, the constraints in expanding Macrobrachium culture is the non-availability of seed to the farmers. The Government has put top priority to encourage establishment of Macrobrachium hatchery for large scale production of seed. FRI has recently developed a prototype backyard prawn (freshwater) hatchery which already has become extremely popular to the progressive prawn seed producers.
With the increase in demand and price in the international market, shrimp culture started expanding since 1970's. According to a survey conducted in 1982-83, the area under shrimp culture was 52,000 ha (Mazid, 1994). Presently land under shrimp culture has increased to about 0.125 m ha. About 75% of this land is located in the Khulna, Bagerhat and Satkhira districts in the south-west and the rest in the Cox's Bazar district in the south-eastern region of the country. The area suitable for penaeid shrimp culture in the country is about 0.20 m ha. In Khulna areas, penaeid shrimp is cultured in the dry season followed by paddy cultivation in the rainy season often with freshwater prawn and in Cox's Bazar area, shrimp and salt are produced alternatively.
The average production of shrimp under traditional culture system as mentioned in the previous section is about 0.20 tons/ha. Some of the private farms initiated semi-intensive shrimp culture in Cox's Bazar area in 1993 and achieved a production of 3-5 tons/ha which opened a new era in shrimp culture (Hussain, 1995). However, the semi-intensive shrimp culture requires high investment in the form of seed, feed and other appliances (aerator, pump, soil/water quality checker, etc.). The greatest problem affecting semi-intensive shrimp culture is the shortage of seeds. Presently, monodon culture almost entirely depends on the collection of wilds seeds. Over-exploitation of shrimp seeds in the natural water is not only causing ecological imbalance but also resulting in severe scarcity. Therefore, in order to sustain the penaeid shrimp culture, establishment of monodon hatchery is an urgent need. Foreign collaboration is very much encouraged for this purpose. However, experiences from other countries show that semi-intensive shrimp culture has a high risk of disease which need highly improved management in respect of water quality management, stocking density, feeding, aeration, water exchange, sludge removal, etc.
In Bangladesh, penaeid shrimp is cultured mostly by extensive, improved extensive and in a very limited scale by semi-intensive method. Under the improved extensive method as developed by FRI, 2-3 juveniles are stocked per m2 in ponds of a few to 50 ha size. With little pond preparation, soil and water quality management, manuring, fertilization and occasional feeding with some water exchange, a production of 500-800 kg/ha is being obtained. This is sustainable and environmentally compatible having no risk of disease.
Fisheries Research Institute is the nodal institution in the public sector and is responsible for conducting and coordinating all fisheries research in Bangladesh and advising the Government in all matters relating to fisheries research and development. The institute practically functioning from 1986 is still in its infancy. In order to carry out its mandated responsibility, the capability of the institute needs to be strengthened in respect of physical research facility creation, procurement of equipment, manpower development and research planning. So, the institute would appreciate any Japanese technical cooperation for its development. It is worthy to mention that many Bangladeshi Scientists have persuade higher studies in the field of fisheries from Japanese Universities but they are not in a position to fully utilize their knowledge and expertise that they have gained during their higher studies in Japan because of inadequate and inappropriate research facilities at home. Presently about 20 FRI Scientists are pursuing higher studies in different Japanese Universities.
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