Dr M. A. Mazid, Director, Fisheries Research Institute, Mymensingh.
Inland pond culture in Bangladesh: experimental work on integrated fish farming at the Fisheries Research Institute, Mymensingh.
Aquaculture plays an important role in nutrition, income, employment and foreign exchange earnings in Bangladesh. Fish contributes approximately 80% of the animal protein intake of the Bangladeshi population, 3.5% of GDP and 9% of export earnings. Approximately 1.4 million people are directly engaged in fisheries; 11 million in part-time fishing and another 3 million in aquaculture. Bangladesh earns about US $ 230 million per annum through the export of fish and fisheries products. The fisheries of Bangladesh are very diverse and are comprised of inland openwater capture fisheries, inland and coastal aquaculture and marine fisheries. These contribute 46.5%, 28.5% and 25% respectively to the total fish production of 1.04 million tonnes.
Freshwater aquaculture consists mainly of polyculture of carps and monoculture of tilapia and various catfish in ponds. Integrated fish farming with paddy-poultry/duck-fish is also practised. An area of 0.15 million ha is currently devoted to pond culture in Bangladesh and yields vary between 5 and 9 t/ha/year in scientific culture. Brackishwater aquaculture mainly involves shrimp cultivation and covers an area of 0.11 million ha. Culture systems are predominantly extensive and semi-intensive, mostly using fertilisation and occasionally both feeding and fertilisation. The giant freshwater prawn and tiger shrimp are cultured mostly by extensive, extensive-improved and semi-intensive methods and yields range from 0.16–5.0 t/ha/yr, depending on management and culture technology. Lack of infrastructure in terms of storage, transport, communication, electricity, marketing and inadequate feed and seed supplies have been identified as major constraints to both fresh and brackish water aquaculture development in Bangladesh.
Map of Bangladesh
Environmental factors which have had a negative impact on aquaculture development are, by and large, caused by man-made interventions in riverine morphology, the disruption of ecology, intensive agricultural practices and modern developments. In addition, natural disasters such as flood, drought and cyclones also have a negative impact. In brackishwater environments, there is very little chemical pollution but soil erosion, heavy siltation, salinity and oxygen fluctuations, mangrove disruption and land use conflicts are emerging as major problems, along with the indiscriminate collection of wild juvenile shrimp. Legislation and regulations for fish conservation are in existence but enforcement is difficult and not many regulatory mechanisms presently exist for protecting aquaculture. A case study on shrimp farming in Bangladesh is included in this report.
Bangladesh is endowed with unique aquatic resources for aquaculture development, but this was not given proper attention until the early 1980s, as enough fish were available through capture fisheries. Production of fish from inland waters, which accounts for around 50% of the total production, started to show a decline in the mid 1980s and this trend has continued, mainly as a result of flood control measures. Other factors contributing to the decline in natural fish stocks were: over-exploitation; abstraction of water for irrigation; intensive agriculture; industrial development; erosion and siltation; reclamation of land for human settlement; pollution; and destruction of mangrove forests. Thus, both the carrying capacity and productivity of the aquatic environment in Bangladesh have been adversely affected.
To compensate for the loss of natural fish production, both public and private sectors initiated efforts to expand aquaculture. These endeavours have been very successful and have resulted in an increase in aquaculture by about 31% over the last 5 years, although its contribution to total national fish production is still only 29%. The future of aquaculture in Bangladesh looks promising with the country possessing 1.3 million ponds (0.15 million ha), oxbow lakes and brackishwater enclosures which have a total area of 0.24 million ha. Scientific fish culture, to optimise fish production, has still to be introduced to over 75% of the fish ponds, which currently have a very low production rate of 0.5–0.6 t/ha/yr.
Shrimp culture under traditional, improved traditional, semi-intensive and intensive methods is being practised in brackishwater ponds. Intensive shrimp culture may, however, have adverse effects on the environment in the future if water quality is poorly managed and maintained. This aspect of shrimp culture needs serious attention in order to circumvent environmental problems. Shrimp culture in brackishwaters also leads to conflict among various farming groups over the use of land for shrimp, rice and salt production. Poor small land holders suffer most since they find it difficult to use their land according to their preferred crop and are sometimes compelled to lease their lands to the affluent and resource rich shrimp farmers. This leads to social conflict and creates an adverse social environment in the area. In order to get hard currency, the Government has increased its support to accelerate the growth of shrimp culture by providing land, credit and materials for development and the establishment of both the shrimp culture and shrimp processing industry. This may further aggravate the prevailing socio-economic conditions in the coastal belt.
3. STATUS OF AQUACULTURE
Aquaculture forms an important sector of the Bangladesh economy and plays a vital role in offering better nutrition, higher income, better employment opportunities and sizeable foreign exchange earnings. Fisheries contribute about 80% to the nation's animal protein intake, nearly 3.5% to GDP and 9% to the export earnings of Bangladesh. Approximately 1.4 million people earn their livelihood from fisheries and another 11 million people are involved in seasonal or part-time fishing and other ancillary activities. An estimated 73% of rural households are engaged in some sort of fishing activity and fisheries comprise around 7% of the total employment (around 28 million) in Bangladesh. During 1993–1994, export earnings from fish and fishery products increased considerably to 9,210 million Taka (US $ 230 million) (Table 1) in foreign exchange, of which 7,840 million Taka (US $ 196 million) was earned from the export of 22,000 tonnes of shrimp, representing around 7.7% of the export earnings.
Table 1. Export data on fish and fishery products in Bangladesh, 1986–1994.
|Total production (tonnes)||23,761||23,423||21,719||23,339||26,109||22,080||26,408||35,923|
|Value (US $ million)||106.0||113.5||118.0||119.7||131.7||131.1||175.0||230.0|
|% of export earnings||12.99||11.93||11.51||9.62||8.64||6.91||7.57||9.12|
The 1992–93 production of shrimp from the sea was 17,600 tonnes, from rivers and inland water bodies is 45,000 tonnes and from coastal shrimp ponds around 20,000 tonnes.
3.1 Fisheries resources
The fisheries resources of Bangladesh are highly diversified in terms of types, resources and nature of the commodities produced. The inland fisheries resources are made up of rivers, estuaries, canals, floodplains, oxbow lakes, reservoirs, inundated paddy fields and ponds covering an area of about 4.3 million ha. Culture fisheries include ponds (0.15 million ha), oxbow lakes (5,488 ha) and coastal shrimp farms (0.11 million ha). Bangladesh has a coastline of some 480 km along the Bay of Bengal, with an area of 64,000 km2. These vast and varied aquatic resources support artisinal and commercial fisheries as well as offering opportunities for aquaculture development. The productivity of the water resources of Bangladesh, by resource and species, is summarised in Tables 2 and 3 respectively.
Table 2. Areas under different fisheries production systems with their contribution to total fish production.
|Source||Water Area (ha)||Production (tonnes)|
|Contribution to total production|
|Inland openwater capture system|
Rivers and estuaries
Beels and Haors
|Closed water resources|
Oxbow Lakes (Baors)
Total Inland Fisheries
According to the latest available statistics, the current level of fish and shellfish production in Bangladesh is around 1.04 million tonnes, 75% of which comes from inland waters and 25% from marine waters. Of the inland production, 69% is from capture fisheries and 31% from culture. While aquaculture production has been steadily rising, showing a growth of 31% over the last 5 years, it's contribution to total production is still only 29%. Production from inland openwater fisheries declined markedly from 0.47 million tonnes in 1983–84, to 0.44 million tonnes in 1985–86. Further scope exists to increase aquaculture production through semi-intensive or intensive culture technologies. Inland aquaculture in Bangladesh extends mainly through: (i) the central districts of Dhaka, Mymensingh, Kishorgonj; (ii) the east and north-eastern districts of Comilla, Chandpur, Noakhali, Feni, Sylhet, Moulavi Bazar, Sunamgonj; (iii) the southern districts of Jessore, Jhinaidah and (iv) the north and North-western districts of Pabna, Sirajgonj, Natore, Rajshahi, Noagoan and Kurigram.
Oxbow lakes (parts of dead rivers which are generally horse-shoe shaped) abound in the country and are mainly located in the south and south-western part, in the districts of Jessore, Jhinaidah, Choadanga, Kustia and Faridpur. There are about 100 oxbow lakes covering an area of 5,488 ha. Due to increasing fishing pressure and a drastic reduction in floodplain (which has resulted in difficulties for fish migration, feeding and reproduction) fish production from these resources has declined considerably. To compensate for this, better lake management practices have been introduced with external stocking of the seed of desirable fish species in around 30 oxbow lakes.
Results have, so far, been promising. The Government has already classified the technology based fish and shrimp farms as industry, allowing them to apply for industrial and bank loans with favourable terms.
Table 3. Fish production by species and source, 1987/88.
|% of Inland/Marine Production||% of total Production|
Other inland fish
Sharks, skates and rays
Other marine fish
|Inland||615,073 tonnes (73.1%)|
|Marine||226,584 tonnes (26.9%)|
The active support of the Government, and the dedicated endeavours of entrepreneurs, has resulted in an expansion of shrimp culture in the coastal belt during the last decade. Recent surveys have shown that the area under shrimp culture has increased from 52,000 ha in 1982–83 to 110,000 ha in 1992–93. the southern districts of Khulna, Bagherhat and Satkhira account for around 75% of shrimp farm area and the remaining 25% is in the south-eastern district of Cox's Bazar.
3.2 Species cultured with culture system
The species cultured in Bangladesh, together with culture systems, are summarised in Table 4. Freshwater aquaculture systems mainly revolve around the polyculture of carps (both Indian and Chinese), popularly known as composite fish culture. This form of culture has been carried out on a commercial scale by many farmers since the late 1980s. Polyculture of carps is practised with varying species combinations and densities, depending on the availability of seed. Supplementary feeding and fertilisation are also carried out and production is usually around 5–6 t/ha. Fingerlings are usually stocked in May/June and the fish are harvested in November/December when temperatures and water levels are low at the onset of winter. Monoculture of tilapia, Puntius sp. and catfish (both African and indigenous) is practised under improved management methods. The production rate for tilapia is around 6–7 t/ha, Puntius sp., 3 t/ha and African catfish 20 t/ha.
Table 4. Species culture and culture systems.
|Species||Common name||Culture System||Intensity|
|Fresh water fish||Catla catla||Catla||Pond culture||Ext/Semi/Int|
|Cirrhinus mrigala||Mrigala||Pond Culture||Ext/Semi/Int|
|Labeo calbasu||Kalbashu||Pond Culture||Ext|
|Labeo rohita||Rohu||Pond Culture||Ext/Semi/Int|
|Ompok pabda||Butter catfish||Pond Culture||Semi|
|Pangasius pangasius||Pangas, catfish||Pond culture||Semi|
|Pangasius sutchi||Pangas, catfish||Pond Culture||Semi|
|Clarias batrachus||Asian catfish||Pond Culture||Ext/Semi/Int|
|Clarias gariepinus||African catfish||Pond Culture||Int|
|Heteropneustes fossilis||Shingi catfish||Pond Culture||Ext|
|Hypophthalmichthys nobilis||Bighead carp||Pond Culture||Semi/Int|
|Ctenopharyngodon idellus||Grass carp||Pond Culture||Semi/Int|
|Cyprinus carpio var Comminus||Common carp||Pond Culture||Semi/Int|
|Cyprinus carpio var Specularis||Mirror carp||Pond /Rice field||Semi/Int|
|Hypophtahalmichthys molitrix||Silver carp||Pond culture||Semi/Int|
|Mylopharnygodon sp.||Black carp||Pond Culture||Semi/Int|
|Oreochromis niloticus||Nile tilapia||Pond/Rice/Cage||Semi/Int|
|O. mossambicus||Red tilapia||Pond Culture||Semi/Int|
|Fresh water shellfish||Macrobrachium rosenbergii||Giant f.w.prawn||Pond/Rice field||Ext|
|Macrobrachium malcolmsoni||Monsoon river prawn||Pond/Rice field||Ext|
|Lamellidens marginalis||Freshwater clam||Pond Culture||Int|
|Brackish water Finfish||Lates calcarifer||Giant sea perch||Embank/Rice||Ext|
|Liza cascasia||Yellow tail mullet||Embank/Rice||Ext|
|Liza oligolepis||Large-scaled mullet||Embank/Rice||Ext|
|Liza tade||Green-back mullet||Embank/Rice||Ext|
|Brackish water shellfish||Penaeus monodon||Tiger shrimp||Pond/embank||Ext/Semi/Int|
|Penaeus indicus||White shrimp||Embank||Ext|
|Scylla serrata||Mud crab||Embank||Ext|
Key: Ext=extensive; Semi=semi intensive; Int=intensive; Embank=embankment culture.
The freshwater prawn (Macrobrachium rosenbergii) is cultured both in monoculture and polyculture with carps, but a very low production rate is currently achieved (0.35 t/ha). However, giant freshwater prawns and tiger shrimp are primarily cultured in brackishwater ponds following traditional and improved extensive culture practices. Production levels under these systems are extremely low ranging from 0.16–0.2 t/ha. Both giant prawns and tiger shrimp are cultured in coastal enclosures, locally called “Gher culture”, where juvenile shrimps are trapped in a large area (covering a few hundred ha) by allowing tidal water ingress into the enclosure. Water is held in the enclosure for 4–5 months so that the prawns and shrimp can grow. Recently, shrimp farmers have initiated semi-intensive shrimp culture using pelleted feeds and have obtained production rates of 5 t/ha, which is comparable to those of any country in the world. Among the finfish group, culture technology of sea bass and mullet in the coastal area is evolving.
3.3 Supply of inputs to aquaculture
Fertilisers, manure and supplementary feeds are supplied to carp polyculture ponds. Pelleted feeds are now available for shrimp culture. Animal offals and viscera of cows and chicken are used in feeding catfish. Carp seed are generally obtained from hatcheries, however, there is a serious shortage of shrimp seed and the current farming is largely dependent on wild seed collection.
According to the FAO/WB Co-operative Programme, more than 1.5 billion post-larvae are collected annually of which 50% die before reaching the shrimp ponds due to rough handling and bad transportation (FAO/WB, 1989). Investigations at the Fisheries Research Institute (FRI) showed that for collecting one post-larvae of P. monodon, 40 other shrimp and 10 other finfish seeds are killed. This poses a serious threat to natural fish and shrimp populations, particularly in the near-shore area. However, freshwater giant shrimp and tiger shrimp seeds are now being produced in hatcheries on a limited scale.
Sale of aquaculture products is still a problem in remote areas where communication is poor and local demand is limited. The marketing of carps is particularly difficult during September and October when these fish are also caught in floodplains all over the country. Shrimp, being a 100% exportable commodity, does not face the same marketing problem, however, small shrimp farmers who sell their products to the processor need to get a fair price. Therefore, a good marketing system with proper transport and storage facilities needs to be developed so that both the producer and processor get a remunerative price.
3.5 Government policy and planning of aquaculture
A new Fisheries Management Policy was adopted in 1986 to ensure direct participation of the fishermen for the maximum utilisation of inland fisheries resources, under a long-term (minimum 3 years) licensing system. The policy aims to augment fish production through the introduction of production orientated biological management systems by replacing the existing revenue orientated systems; 264 fisheries are now being managed under this policy. The “Cabinet Committee on Finance and Economic Matters” has recently made a number of recommendations for overall development of the fisheries sector. These recommendations have been approved by the Honourable Prime Minister of the Government of Bangladesh. Recently, a draft “Fisheries Development Policy” has been formulated describing the role of the public and private sectors in aquaculture and fisheries development, management and conservation. The policy is now under the active consideration of the Government for adoption.
Fish production from inland openwaters has been on the decline, for reasons previously mentioned. In order to enhance fish production, the Government started stocking selected openwater bodies with carp fingerlings in 1988. During 1992–93, 90 million fingerlings were stocked in a number of floodplains. The Department of Fisheries (DOF) has maintained some fish sanctuaries for conservation of resources for natural recruitment.
The following priorities are set in the current Five Year Plan (1990–1995):
To increase fish production for domestic consumption.
To improve the socio-economic conditions of fishermen and others engaged in fisheries and create additional employment opportunities for poverty alleviation.
To enhance the fisheries resource base through extension of commercially important fisheries in unexplored and under-exploited areas.
To enhance fish production and management technology.
To train the required manpower at all levels for facilitating the transfer of technology.
To increase foreign exchange earnings through the export of fish and fisheries products.
To improve the general environment and public health.
3.6 Legal framework
A Fish Conservation Act under the title “East Bengal Protection and Conservation of Fish Act, 1950” was formulated and promulgated in 1950. A list of current legislation formulated and enacted for the management and development of fisheries and aquaculture is provided below:
|1.||East Bengal Protection and Conservation of Fish Act, 1950.||Described licensing system for specific fisheries. Prohibits or regulates use of fixed engines; construction of dams and embankments; prohibits the destruction of fishes by explosives, poisoning, effluents, banning of fishing season and size of fish etc. and provision of penalties for breaching of any such regulations.|
|2.||The Protection and Conservation of Fish (Amendment) Ordinance, 1982.||Made certain amendment to the above to increase the effectiveness of the above Act.|
|3.||The Tank Improvement Act, 1939 (modified up to 1964).||Described the authority of the Govt. to take possession of any derelict pond if any owner does not undertake its improvement. Also can lease out those to interested persons willing to undertake improvement for aquaculture.|
|4.||The East Bengal Fisheries Development Corporation Ordinance, 1964.||Ordinance under which FDC was created which also described its functions and responsibilities.|
|5.||The Bangladesh Fisheries Development Corporation Act, 1973.||Ordinance under which the Fisheries Development Corporation was created which also described its functions and responsibilities.|
|6.||The Tank Improvement (Amendment) Ordinance, 1986.||Made amendment to the above to increase its effectiveness.|
|7.||The Protection and Conservation of Fish Rules, 1985.||Described rules and regulations for conservation of fisheries.|
|8.||The Marine Fisheries Ordinance, 1983.||Described regulation for licensing and management of marine fishery, operation of mechanised or non-mechanised boats etc, prohibits fishing methods, marine reserve etc.|
|9.||The Marine Fisheries Rules, 1983.||Regulations for fishing vessels, equipment, crew, fishing operations, species and quantity of fish to harvest, period of license, area of fishing, description of joint venture etc.|
|10.||The Fish and Fish Products (Inspection and Quality Control) Ordinance, 1983.||Described the quality standard for frozen fish and fishery products and the authority of the quality control inspector in regard to maintain product quality.|
|11.||Fish and Fishery Products (Inspection and Quality Control) Regulations, 1989.||Regulations for maintenance of product quality.|
|12.||The new fisheries management policy, 1988.||Made provisions for leasing fisheries to genuine fishermen.|
|13.||Aquatic environment protection law.||Monitoring freshwater environment and observation on coastal zone management.|
The Ministry of Environment and Forest announced an Environment Policy in 1992 and an implementation schedule for conservation and development of the environment. The Department of the Environment under the Ministry of Environment and Forest is responsible for overall development and protection of the environment in Bangladesh, however, the present emphasis of the department is more on control of industrial and other chemical pollution. Under the present system, different aspects of environmental impact are examined carefully before undertaking a new development project, however, EIA is not mandatory for an aquaculture project.
The DOF is also responsible for overseeing the degree of intensification of aquaculture practices and its impact on the environment and is entrusted with the responsibility of framing regulations to control adverse impacts.
3.7 Fish health
Presently no quarantine is practised for imported fish.
Quality control of frozen prawn and fish for export is administered by the DOF, using standard bacteriological examination procedures. Bacteriological examination is performed for the presence of coliform, Vibrio, Shigella and Salmonella on fish muscle, gills, body surface and other parts.
3.8 Major institutional framework governing fisheries and aquaculture
|Fisheries Research Institute (FRI).||Aquaculture research and development.|
|Directorate of Fisheries (DOF).||Development and management of aquaculture.|
|Bangladesh Fisheries Development Corporation (BFDC).||Product development, quality control and marketing.|
|Bangladesh Agricultural Research Council (BARC).||Co-ordination, monitoring and evaluation of aquaculture research.|
|Faculty of Fisheries, Bangladesh Agricultural University.||Fisheries education and research.|
|University of Dhaka.||Fisheries education and research.|
|Institute of Marine Science, University of Chittagong.||Marine fisheries education and research.|
|Universities of Rajshahi and Khulna.||Fisheries education and research.|
|Bangladesh Rural Advancement Committee.||Aquaculture extension and development.|
|Mennonite Central Committee.||Aquaculture extension and development.|
|Proshika Manobik Unnayan Sangstha.||Aquaculture extension and development.|
4. INTERACTIONS BETWEEN AQUACULTURE AND THE ENVIRONMENT
Industries are being developed at a rapid rate in Bangladesh, causing damage to the environment through pollution. Aquatic pollution from oil spills and the release of effluents have been increasing daily, posing a potential threat to aquaculture. Conversely, intensification of aquaculture also contributes to environmental degradation. In particular, freshwater fish culture poses a potential health hazard in Bangladesh, as most people still use pond waters for washing, bathing and sometimes drinking.
Presently, most industrial effluents are discharged into rivers untreated, leading to degradation of the aquatic environment. Therefore, the impacts of such pollution and the extent of damage needs to be properly assessed and documented. This is essential for sustainable aquaculture development.
4.1 Impact of the external environment on aquaculture production
4.1.1 Inland aquaculture
Aquaculture in Bangladesh faces high risks since the country suffers perennially with floods and droughts. Ponds in flood-prone areas, particularly in the southern part of Bangladesh, are subject to flooding every year which discourages people from investing in aquaculture. Conversely, most of the ponds in the country dry up during the dry season due to prolonged drought conditions, making aquaculture difficult. It is thus important to offer pond production models which are well adapted to flooding and dry season risks and provide profitable remuneration through fish culture.
Heavy siltation due to erosion and the construction of a large number of Flood Control and Drainage (FCD) and Flood Control, Drainage and Irrigation (FCDI) structures, has impeded the feeding and breeding migration of many important fish and prawns to the floodplains, with a negative effect on stock recruitment. The estimated total area under floodplain was almost 6.3 million ha, but this has been reduced by 0.81 million ha by flood protection measures (MPO, 1987). It has been estimated that 2.0 million ha of floodplains will be lost to fisheries due to water development projects by the year 2005, with a consequent loss of production of over 1.0 million t/year. Again, dry season irrigation depletes many small water bodies which hold fish broodstock.
Construction of the Farakka barrage in India also adversely affected migratory fish in Bangladesh. This was particularly serious during the dry season. Acidic soil in certain areas and sandy soils in other areas of the country are also a constraint to aquaculture development.
Human and agrochemical pollution
The disposal of human wastes in Bangladesh, with the exception of some parts of the cities, is not satisfactory. Human excreta discharged into septic tanks ultimately finds its way into rivers or the sea. The total estimated BOD load from domestic wastes in the Karnaphuli River is about 3.5 million t/day in the dry season. The fish catch in the Karnaphuli is diminishing as a consequence of dissolved oxygen depletion in the river water caused by decomposition of sewage and domestic wastes.
The country has around 2.83 million ha of rice fields, which retain water from 4–6 months from April to September during the monsoon. Farmers used to catch wild fish from rice fields and some estimates put these harvests at 37 kg/ha. The farming of high yielding varieties (HYV) of rice, with the concomitant use of insecticides and pesticides, has resulted in the total disappearance of fish from such rice fields. However, farmers have recently initiated integrated rice-fish farming by stocking rice fields with fast growing species of fish. Fish yields of over 0.1 t/ha have been attained.
The use of pesticides and fertilisers in rice fields is increasing daily in Bangladesh, with 4,000–5,000 tonnes and 242 different types of pesticide used annually. An estimated 1.6 million tonnes of fertilisers are used annually. The use of pesticides is important for crop protection, but improper doses or unapproved chemicals are harmful to fish and other aquatic fauna. In a survey it was revealed that the killing of fish with pesticides occurs mainly as a result of: the use of pesticides in improper doses; the use of banned chemicals; and aerial spraying of chemicals for mosquito control. Organochlorine chemicals are highly toxic to fish and other aquatic organisms and in sub-lethal doses may affect the reproductive physiology of fish. A list of pesticides, which are effective for rice insects and cause varying degrees of harm to fish, is shown in Table 5.
Table 5. Common pesticides used in Bangladesh.
|Harmful Pesticides||Relatively safe pesticides|
|Name||Dose (per hectare)||Name||Dose (per hectare)|
|Heptachlor||4.5 kg||Dimacron||840 ml|
|Dieldrin||4.5 kg||Sumithion||1.12 litres|
|Basudin||16.8 kg||Malathion||1.12 litres|
|Diazinon||1.68 litres||Nogos||560 ml|
|Sumisidin||250 ml||Furadan||16.7 kg|
|Ripchord||560 ml||Sedin||1.3 kg|
Toxic industrial wastes
Fish kills and the accumulation of toxic substances in fish have been recorded in the five industrial zones of Dhaka, Chittagong, Narayangonj, Khulna and Ghorasal. Industrialisation, urbanisation and the use of chemicals are increasingly polluting the aquatic environment through the indiscriminate dumping of all forms of solid and liquid wastes into rivers. Water quality standards for fish life are shown in Table 6.
Table 6. Standard values for different parameters for fish life.
(all parameters in mg/l unless otherwise stated)
|Standard Value For Fisheries|
|Acidity||Less than 20|
|Alkalinity (total)||70 – 100|
|Chloride (as Cl)||600|
|Total Coliform (mg/100ml)||5,000|
|Electrical conductivity (mmhos/cm)||800–1,000|
|Hardness (as Ca CO3)||80 – 120|
|Oil and grease||0.01|
Source: Department of Fisheries, Bangladesh.
The major industries causing chemical pollution to the aquatic environment include: paper and pulp mills; rayon mills; tanneries; fertiliser factories; pharmaceutical factories; jute mills; textile mills; sugar mills; steel mills; rubber industries; chemical industries; fish processing industries; oil refineries; machine tool factories and soap factories. Most of these industries do not have waste treatment plants and thus discharge untreated industrial wates and effluent and domestic organic wastes (sewage) directly or indirectly, through canals or drains, to the rivers or other water bodies. These discharges do not, however, directly effect pond culture.
Sylhet pulp and paper mills at Chatak, Karnaphuli paper mills at Chandragona, fertiliser factories at Fenchugonj and Ghorashal and Hazaribag tanneries in Dhaka contributed to the depletion of the fishery resources of the rivers Surma, Karnaphuli, Kushiara, Sitalakhya and Buriganga, respectively. A large-scale mortality of fish at Sitalakhya river was due to the release of raw ammonia from a urea fertiliser factory at Ghorasal (Ali, 1991). Fish mortalities in waterways near Mubarakgonj sugar mills in Jhenaidah and Setabgonj sugar mills in Dinajpur district, are due to the effluent discharged from these mills (Ali, 1991). The discharge of mercury to the Karnaphuli river by the Chittagong Chemical Complex and KPM, lead from oil refineries, chromium from tanneries, cadmium from dyeing and painting and arsenic from urea fertiliser factories are also polluting the aquatic ecosystems of Bangladesh (ESCAP, 1988).
Pollution by oil
The main sources of oil pollution are refineries, garages, discharges from tankers and navigation. It has been observed that the major rivers and estuaries in the vicinity of Chalna and Chittagong port receive waste oil from ships, tankers and refineries and, as a result, the water becomes blackish and polluted.
4.1.2 Coastal aquaculture
Coastal aquaculture, i.e. the trapping and holding of shrimp, has been in vogue for the past few years and has expanded rapidly due to the high demand and price for shrimp. Tidal lands with embankments for the protection of rice fields from brackishwater intrusion are increasingly being used for shrimp culture, which has led to land-use conflicts. Shrimp farming has rendered many lands unfit for rice cultivation and also reduced the land available for grazing cattle. Trees and other plantations are also affected by the holding of saline waters in fields. It is also reported that potable water is becoming more saline in some areas.
In the south-eastern part of the Cox's Bazar area, considerable areas of mangrove forest have been destroyed by construction of shrimp ponds. Table 7 shows the types and situation of forests in Bangladesh. High water turbidity in the rivers, as a result of carrying approximately 2 billion tonnes of silt every year from upstream, is a major constraint in terms of water quality. It is detrimental to fish productivity and the nursery grounds of the fish. High fluctuations in salinity is another important constraint to all year round aquaculture production. Shrimp culture in coastal areas is predominantly dependent on the collection of juveniles from the wild which causes a serious depletion in the natural stocks of both fish and shrimp. Cyclones and tidal bores are very common in coastal areas and they cause damage to shrimp farms.
Table 7. Types and Situation of forest in Bangladesh (Bari, 1993)
|Type||Situation||Main tree species|
(× 106 ha)
|Hill forests||Greater Chittagong, Chittagong Hill; Tracts and Sylhet districts.||Garjon, Chapalish, Dhakijan, Jarul, Koro, Shegun etc.||0.67|
|Natural mangroves||Greater Khulna and Patuakhali districts.||Sundari, Keora, Baen, Gewa, Passur etc.||0.56|
|Man-made mangroves||Greater Barisal, Patuakhali, Noakhali and Chittagong districts and coastal areas of Chittagong district.||Keora, Been and Gewa.||0.11|
|Inland sal forests||Greater Dhaka, Mymensingh, Tangail, Rajshahi, Dinajpur and Rangpur districts.||Sal and its associates including Koroi.||0.12|
|Total||1.46× 106 ha|
4.2 Contamination of aquaculture products
Cases of serious contamination of aquaculture products have not so far been reported. However, systematic studies need to be undertaken in this respect. Similarly, the presence of heavy metals both in freshwater and marine fish is not commonly reported. Since there is little industrialisation in Bangladesh, the level of such contamination is assumed to be low, but there is a need for systematic study.
It has been reported that the consumption of freshwater patkafish (Tetraodon patoca) often led to death, but this was not due to contamination. The fish has a sub-cutaneous poison gland and it also contains poison in the liver and gonad. Due to people's ignorance about this fact, the fish were consumed with the poison gland. People are now being given advice about the process of separating the poison gland from the consumable flesh of the fish.
4.3 Impact of aquaculture on the environment
4.3.1 Inland aquaculture
Physical and chemical factors
Oxygen depletion during prolonged rains and algal blooms are a common occurrence in Bangladesh. Manuring and fertilisation of ponds and the feeding of fish also result in plankton blooms.
Table 8 shows the chemicals that are currently used in freshwater aquaculture in Bangladesh. No deleterious effects have been documented so far.
Table 8. List of chemicals commonly used in aquaculture in Bangladesh.
|Dipterex||0.5 ppm||To control ectoparasites.|
|Rotenone||3.0 ppm||To kill fish.|
|Phostoxin||1 tab/210 ft3||To kill fish.|
|Malachite green||0.5 – 1.0 ppm||To control fungal and parasite infections.|
|Copper sulphate||0.5 – 1.0 ppm||To control bacterial and parasite infections.|
|Terramycin||15.0 mg/kg fish||To control bacterial infection.|
Interactions between aquaculture and native species
Exotic species like silver carp compete for feed with local Catla catla and common carp with Cirrhinus mrigala. The exotic African catfish (Clarias gariepinus) is a voracious eater. Aquatic biodiversity is threatened with the introduction of exotic fish.
Social conflicts and aquaculture
The pond waters in rural areas are mostly used for household purposes. Application of cow dung and other chemicals prevent the farmers from using the water for household and sometimes drinking water purposes. Conflicts can arise over the use of water for crop production where people tend to irrigate crops. There is less competition between aquaculture and industry.
4.3.2 Coastal aquaculture
Physical and chemical factors
Disruption of mangrove causes soil erosion, siltation and salinity and oxygen fluctuations. The intake of freshwater to coastal shrimp ponds and the exchange of water in the farm leads to increases in salinity and land subsidence.
The chemicals used in coastal aquaculture are similar to those used in freshwater aquaculture. Due to extraneous feeding and improper maintenance of water quality, the condition of the pond sediments deteriorates. Heavy siltation also has adverse effects on the BOD and COD profile of the pond.
Interaction between aquaculture and native species
No exotic species of shrimp have been introduced into Bangladesh.
Social conflicts and coastal aquaculture
Coastal shrimp farms are generally very large. Affluent entrepreneurs from urban areas often acquire land leases from resource-poor land owners. In addition, the intake of saline water into the shrimp ponds also affects nearby paddy fields. The small paddy owners are unable to resist this, which creates social tensions.
There is growing conflict among groups of people depending on mangrove forests, rice cultivation and salt production with shrimp farmers and entrepreneurs. The land-less people, or agricultural labourers, become jobless with the reduction of paddy cultivation. More and more areas are being brought under shrimp culture, damaging terrestrial plantations and shrinking agricultural and grazing lands by the intake of saline water. Salinisation also prevents vegetable gardening and has a detrimental effect on some trees such as mango and date.
5. INTERACTIONS BETWEEN AQUACULTURE AND THE ENVIRONMENT: IN-DEPTH STUDY
5.1 Shrimp culture in Bangladesh
5.1.1 History of shrimp culture in Bangladesh
Bangladesh has extremely favourable conditions for shrimp culture with low production costs. Prior to the construction of coastal embankments, traditional shrimp culture in a limited area has been popular in the coastal district of Satkhira. Under the traditional system, tidal water carrying shrimp juveniles and finfish is allowed to enter during February to April through the sluice gates of the embankment. The trapped juveniles are allowed to grow for about four months before harvest. After the shrimp are harvested, the land is used for rice cultivation during July to December. Coastal embankments, constructed to increase rice production, adversely affected the natural life cycles of many fish and prawns inhabiting the seas and the estuaries.
As a result of increases in demand and price, shrimp culture started to expand in the 1970s. According to a survey conducted in 1982–83, the area under shrimp culture was 52,000 ha. Presently, land under shrimp culture has increased to about 0.11 million ha. About 75% of this land is located in the Khulna, Bagerhat and Satkhira districts in the south and the rest in the Cox's Bazar district in the south-eastern region of the country. According to some estimates, the area suitable for shrimp culture in Bangladesh is around 0.2 million ha. In Khulna areas, shrimp is cultured in the dry season and paddy in the rainy season and in the Cox's Bazar area, shrimp and salt are produced alternately.
5.1.2 Economic importance
Shrimp play an important role in the economy of Bangladesh and have become the third largest export earner. In 1993–94, the country earned about US $ 196 million from the export of shrimp, which is 7.8% of the total national export earnings and 86% of the export earnings from fish and fishery commodities. The present shrimp catch from the sea stands at 17,600 tonnes. The production from coastal shrimp farms is about 20,000 tonnes.
5.1.3 Types of technology
Shrimp culture practices include: (1) extensive (traditional); (2) extensive (improved); (3) semi-intensive; and (4) intensive systems.
The ponds are fed tidally and size varies from a few ha to over 100 ha. Collection of seed is done mostly by trapping from the wild at high tide. No liming, fertilisation and feeding are carried out and some water is exchanged at spring tide. Production is very low ranging from 0.06 – 0.2 t/ha/year.
Ponds are usually a few ha to 50 ha in size and are normally tidally fed. Smaller ponds at higher elevations are sometimes fed with a pump. Two to three juveniles are stocked/m2. Lime and fertilisers are used and feeding is also done, but not systematically. About 50% of the pond water is exchanged during each spring tide cycle or 5–7 cm of water is exchanged every alternate day. Production is usually between 0.6–1.0 t/ha/year over two crops.
In this system, 10–35 post-larvae/m2 are stocked in smaller ponds, with sizes ranging from 0.4–5.0 ha. They are given mostly pelleted feed but they also partly subsist on natural foods. The ponds are generally aerated and 10–20% of water is exchanged daily by gravity drainage. Yields of 2–5 t/ha/yr are commonly obtained.
Above 35 post-larvae/m2 are stocked in intensive pond systems, with ponds of 0.1 ha to 5 ha in size. Water is aerated and at least 30% of pond water is exchanged daily. Shrimp are fed entirely with artificial feed and production is about 5–10 t/ha/year.
Improved traditional and semi-intensive shrimp culture need quality feed, which is in short supply. Presently, only 10% of the total feed required by the shrimp farming industry is produced in the country. Fish meal, the major ingredient of shrimp feed is constrained because of the scarcity of fish meal.
During the last twenty years, shrimp culture practices have changed from traditional to improved traditional and there is increasing emphasis now on semi-intensive systems. The introduction of intensive systems is anticipated shortly, which emphasises the need for proper attention to the maintenance of water quality and disease control.
5.1.4 Management and legal regime for access to shrimp culture
Government owned tidal lands are leased out for shrimp culture. In the Cox's Bazar area, three size categories of land (i.e. <10 acres; 11–32 acres and >33 acres) are leased out for a ten year period. The Government has introduced a new Fisheries Management Policy for licensing fisheries based on a production orientated biological management plan, replacing the revenue oriented system. The license for allocation of coastal land in the Cox's Bazar area is issued by the Department of Fisheries under the Ministry of Fisheries and Livestock, which has already leased 6,715 ha, whereas the Ministry of Land has leased out 5,800 ha. In the Khulna region, entrepreneurs take leases directly from private land owners and establish shrimp farms.
5.2 The environmental impacts of shrimp culture
Indiscriminate killing of wild fish seed
In the absence of adequate numbers of functional hatcheries, and with the rapid expansion of shrimp farming, the collection of wild tiger shrimp post-larvae from estuaries and near shore waters has increased tremendously, leading to the destruction of shrimp and other finfish species. An investigation by the Fisheries Research Institute showed that in the collection of one P. monodon post-larvae, 40 other shrimp and 10 other finfish seeds are killed, which has led to a serious depletion of natural populations of both shrimp and finfish, particularly in the near shore area. It has been estimated that more than 1.5 billion post-larvae are collected annually in Bangladesh, of which 50% die before reaching shrimp ponds because of rough handling and bad transportation. Strategies to reduce mortality rates are badly needed.
Imbalance in coastal ecology
The unplanned growth of shrimp culture has a serious effect by altering the coastal ecology. Tidal land previously used for rice cultivation has been changed to shrimp farms and inundation of rice fields by saline water has become a common occurrence.
A large number of people, both male and female (and including children), are increasingly becoming engaged in fry collection. Net dragging by thousands of fry collectors every day causes river erosion and increases siltation.
Adverse effects on biodiversity
Table 9 shows the aquatic and semi-aquatic animal species in Bangladesh. About twelve fish species are considered as endangered/threatened due to their gradual disappearance as a result of change or conversion of habitat and degradation of environment.
Table 9. Diversity of aquatic and semi-aquatic animal species. (Ahmed, 1993).
|Animal Groups||Habitat||Species Number|
|Shrimp||Freshwater and marine||56|
|Fish||Freshwater||260+13 exotic species|
|Turtles and Tortoise||Freshwater||24|
|Birds||Freshwater and marine||200|
|Others||Freshwater and marine||3|
Although fry collection from the wild presently provides some employment, this is not significant compared with the loss that may result in the form of ecological alteration, environmental degradation and changes in the natural balance of fish populations.
In order to reduce the adverse impacts of shrimp fry collection, the Government is planning to expand its support to establish hatcheries in the private sector. Establishment of shrimp estates for private hatcheries and construction of the required infrastructural facilities for the private entrepreneur are included in the Government plan. The plan also demarcates land which is considered suitable for shrimp farming and specifies the management method to be used in a particular area.
Adverse effects caused by the removal of mangroves
The Sundarbans mangrove forest in Khulna, the south-western part of the country, covers nearly 60,000 ha, and is the largest single mangrove resource in the world. The south-eastern part, the Chakaria Sundarban in Cox's Bazar, has a mangrove area of 7,500 ha. The coastal belt along Barisal, Patuakhali, Noakhali and Chittagong districts has about 110,000 ha of mangrove forest. The mangrove has been reduced by over exploitation, housing settlement, expansion of shrimp culture and other development works in the coastal area related to cyclones, tornadoes and tidal bores.
Once the Chakaria Sundarban had a dense mangrove forest of 18,200 ha. With the expansion of shrimp farming since the 1970s, over 50% of the mangrove has been cleared for the establishment of shrimp farms and now only a small patch of forest remains in the interior. The natural breeding grounds have been lost to a great extent. The clearing of the mangrove resulted in an increased vulnerability to cyclones and tidal waves. Increased salinity has been caused by longer retention of saline water and greater evaporation and acidification of surface waters. The conversion of mangrove forests would appear to be uneconomic if the potential yields are compared with the combined yields of the forests and traditional fisheries which are now both lost.
The recent upsurge of shrimp farming has also created certain problems and conflict with other farming systems such as rice cultivation and salt production.
5.3 Description and diagnosis of environmental impacts related to the discharge of shrimp farm effluents
Semi-intensive and intensive culture systems employ occasional water exchange. Intensive culture systems (which are now taking off in Bangladesh) use some pond preparation, water quality management, supplementary feeding, aeration and regular water exchange. Although noticeable environmental problems have not been observed yet, signs of increased salinity in the enclosure where the same land was used for paddy cultivation, and deposition of organic matter and nutrients are there. Proper engineering design of the pond and farm is essential. The “nutrient sink” concept has to be adopted to utilise the effluent from the farm.
5.4 Description and diagnosis of environmental impacts related to the use of land for shrimp farming
As stated previously, large areas of tidal land are converted to shrimp farms by dyking the land which forms a large single sheet of water with no compartments. These lands used to be used for rice and salt production in Cox's Bazar and shrimp and rice production in Khulna, Satkhira and Bagerhat districts. Under semi-intensive culture systems, a cluster of ponds with manageable water areas is constructed.
The high rate of economic return in shrimp farming is constantly inducing farmers to convert more and more paddy field into shrimp farms. This has resulted in over exploitation of shrimp juveniles from the wild leading to ecological imbalance, a change in the cropping pattern, conflicts of interest, leasing of land from small farmers depriving them of their right to own land and other socio-economic and environmental consequences. The Government is planning to demarcate land for shrimp farming and shrimp hatcheries to resolve these socio-economic conflicts and conserve coastal fishery resources.
Research and extension services are being strengthened in order to improve farm management practices in an attempt to mitigate the negative environmental impacts discussed above.
6. PRIORITIES FOR DEALING WITH ENVIRONMENTAL PROBLEMS
Appropriate research needs to be conducted for sustainable development and to address possible negative impacts. Research on coastal aquaculture development and management is still in an early stage and the actual status of aquaculture development and the extent of impacts on the environment need to be assessed, monitored and documented. This would provide baseline information which could be used to determine and develop appropriate as well as environmentally friendly technology.
The Government should register all shrimp farms, carry out environmental monitoring and allow farms which have no environmental impacts to continue operating. The financial institutions should grant financial assistance to the aquaculture industry based on skills and efficiency in environmental management.
6.1 Prevention and cure of the detrimental effects on aquaculture of man-made changes to the environment and environmental impacts of aquaculture
6.1.1 Detrimental effects on aquaculture
Preventative and mitigating action is needed to redress the problems related to the construction of flood control structures, such as:
Reclaimed land in fisheries habitats.
Destroyed spawning and nursery grounds.
A reduction in fisheries habitats.
An end to natural fish recruitment.
Reduced natural fish food organisms like aquatic insects, molluscs and invertebrates.
The endangered resource base has to be protected and the loss of fisheries by the FCDI projects has to be properly assessed and compensated for by the development of culture-based capture fisheries. Deforestation has caused increased soil erosion, turbidity, siltation, water temperatures and salinities, which have affected the propagation of fish and destroyed their natural breeding and nursery grounds. To maintain a proper ecological balance, the Government is pursuing a forest conservation, expansion, development and plantation programme.
Heavy siltation during the monsoon causes inflammation of the gills which can kill young fish, reduce the natural productivity of the waterbody and increase bacterial growth. Measures need to be taken to reduce soil erosion and consequent siltation.
Cultivation of HYV paddy has increased the use of fertilisers and pesticides, resulting in mortalities of fish in paddy fields. It is essential that fertilisers, pesticides and other artificial inputs that affect living aquatic organisms and soil and water fertility are used judiciously. Biological pest management should be introduced and the wilful destruction of fish stocks by poisoning, which is sometimes a cause of social tension, should be stopped.
The introduction of exotic fish species has resulted in increased competition for feed and survival, threatened the survival of indigenous fish, changed the compatibility of species and altered natural biodiversity. Other man-made changes result in intersectoral conflicts between forestry, fisheries and agriculture, through the conversion of rice field into fish ponds, the conversion of river shores into rice fields causing siltation to rivers, increased competition for manure and feed ingredients and the salinisation of freshwaters.
6.1.2 Prevention and cure
Major mitigation measures which are planned or should be undertaken
Construction of fish passages or fish ways in the flood control structures.
Undertake planned aquaculture in reservoirs, borrow pit canals and other waterbodies created by construction of dams, embankments and other water control structures.
Provision of such arrangements in new flood control structures.
Introduction of rotational fish-shrimp cropping.
Artificial stocking of floodplains and reservoirs.
Undertake and expand integrated livestock-fish and rice-fish farming activities.
Development of fish sanctuaries.
Protection of fish habitats.
Maintenance of water quality and regular monitoring.
6.2 Aquaculture causing harmful changes to the environment
The destruction of mangrove for the construction of shrimp farms is of great consequence as is the shrinking of grazing land and destruction of inland forests. The horizontal expansion of traditional extensive shrimp farming absorbs grazing land and adversely affects fruit bearing trees, due to prolonged retention of saline water. Coastal embankments, which were originally constructed for flood protection and to prevent tidal water incursion for rice production, are now being used to trap tidal water for shrimp production.
The lack of hatchery produced shrimp on one hand, and the expansion of shrimp culture in coastal areas on the other, has increased pressure for the collection of wild seed.
6.2.2 Major mitigating measures planned or undertaken
Establishment of shrimp hatcheries.
Reduction in the harvest of wild shrimp seed.
Formulation of appropriate land-use policies.
Reduction of farm size for more efficient operation.
Conservation and development of mangrove forest.
Development of appropriate shrimp culture technology.
Soil and water quality management.
Rotational shrimp and fish culture.
7. FUTURE AQUACULTURE DEVELOPMENT PLANS
The present fish production of 1.04 million tonnes has to be increased to keep pace with demand from the country. Potential exists to greatly increase aquaculture production but as yet there is no Bangladesh Aquaculture Development Plan similar to that prepared by FAO for Asia in 1975.
The Ministry of Fisheries and Livestock has been pursuing the following policies for the development of aquaculture:
Taking control of Government owned water bodies, presently under the management of other agencies, for the purposes of aquaculture development.
Preparing a Fish Culture Manual for the different agencies to enable them to undertake aquaculture in water bodies under their control.
Set up shrimp hatchery estates and shrimp culture zones.
Large-scale dissemination of finfish and shrimp culture technologies to the rural farmer.
Development of culture based capture fisheries in oxbow lakes and reservoirs created from the construction of flood control and other water development structures.
Ensure institutional financing for aquaculture development by the private sector.
Carry out research to evolve environmentally compatible appropriate technologies.
The Government has formulated an Environment Policy, (1992) for the protection, conservation and development of the environment and to ensure maintenance of environmental quality in all development activities.
7.1 Development activities
Some of the major fisheries development and research activities are listed below:
|1.||Shrimp culture project.||To expand shrimp culture in Khulna and Cox's Bazar districts through improved methods. Establishment of one shrimp hatchery in the public sector and 30 hatcheries in the private sector.|
|2.||North-west aquaculture project.||To establish hatchery and extension of aquaculture technologies to the north-western districts of Bangladesh.|
|3.||Second aquaculture development project.||Artificial stocking of fingerlings in floodplains of Mymensingh and Sylhet districts to increase production. Establish fish and shrimp demonstration farms in 15 districts, including 5 coastal districts, to demonstrate improved aquaculture technologies to the farmer.|
|4.||Integrated aquaculture development project.||Establishment of 16 hatcheries, extension of aquaculture through providing technical and material support and undertake aquaculture within 4 irrigation project areas through artificial stocking.|
|5.||Oxbow lake development and management project.||Development of culture-based capture fisheries in 30 oxbow lakes in greater Jessore, Kustia and Faridpur districts through artificial stocking and improved lake management.|
|6.||Aquaculture extension project in Mymensingh district.||Extension of pond culture technologies to the farmers of Mymensingh district through providing credit, demonstration and training.|
|7.||Third fisheries project.||To increase the productivity of floodplains in the north-west and south-western districts through artificial stocking and conduct research on the productivity, gear selectivity, disease and impact of such in the floodplain.|
|8.||Integrated aquaculture.||Development of aquaculture in the flood development in the irrigation protection area and flood control project area.|
7.2 Research activities
Some of the on-going research activities related to aquaculture development follow:
Genetic improvements of carps by chromosome manipulations.
Survey of fish diseases and parasites in freshwater ponds of Bangladesh.
Development of techniques for the culture and breeding of catfish, Gulsa, Pabda and tilapia.
Development of cost-effective feeds from indigenous raw materials for fingerling and adult carps.
Development of integrated livestock-fish farming.
Development of nursery pond management methods for optimising production of fry/fingerlings of carps.
Polyculture of cultivated fish species for optimising production from ponds.
Development of techniques for the breeding and culture of Clarias batrachus and C. gariepinus.
Development of breeding and culture of Masheer (Tor putitora) and maternal effect study in Mrigal (Cirrhinus mrigala).
Socio-economic impact and constraints of shrimp culture in Bangladesh.
Survey and assessment of shrimp fry resources of Bangladesh.
Development of culture techniques for tiger shrimp (P. monodon).
Pond culture of Macrobrachium rosenbergii.
Freshwater aquaculture research is progressing exceedingly well. However, research on shrimp culture and other coastal finfish breeding and larval rearing, coastal aquaculture, coastal ecology, coastal socio-economics and coastal zone management, need to be strengthened. Three tiers of training would be beneficial for aquaculture development and management.
Training for administrators and planners.
Training for scientists and extension workers.
Training of farmers.
Research studies have generated considerable amounts of useful information on aquaculture management, which are now available for exchange at national and regional level for mutual benefit. An effective mechanism for regional information exchange needs to be further strengthened.
8. GENERAL RECOMMENDATIONS
Different categories of shrimp hatchery, based on production capacity, should be established.
Destructive fishing of shrimp seed from the wild should be stopped, or regulated at a sustainable level.
Nursery and larval rearing technologies for shrimp need to be developed.
Facilities for water quality monitoring and EIA should be strengthened in the region.
Super-intensive aquaculture practices have to be avoided for environmental reasons.
Appropriate land-use patterns have to be introduced to resolve socio-economic conflicts. Aquaculture and shrimp culture zones have to be demarcated and established. There should be a mandatory mangrove afforestation programme for the shrimp grower in places where mangrove forests have been destroyed.
Acute shortages of fish feeds require the establishment of feed mills for the production of cheaper and better quality feeds.
Liberal Government or bank financing should be extended to the private entrepreneurs for brackishwater aquaculture development.
Insurance schemes should be introduced for aquaculture.
International support and collaboration are needed for sustainable aquaculture development, pollution control, monitoring and assessment of environmental impact and to evolve mitigatory measures.
The Government should provide basic facilities like dykes, canal and road construction, power and water supply for the development of aquaculture.
Chemical fertilisers may be gradually replaced by bio-fertilisers. Non-biodegradable pesticides should be replaced by biodegradable ones and integrated pest management systems should be practised.
The indiscriminate use of fertilisers should be stopped.
The industry should adopt appropriate measures for the proper disposal of industrial wastes, following standard procedures.
Agricultural residues should be converted to fish feed and manure.
Industrial wastes should be recycled or converted into other useful products through the promotion of research.
Appropriate regulation of oil spills in coastal areas should be established and implemented to minimise marine pollution. Fish ways and passes should be constructed in existing dams and embankments.
Provision should be made in designing new water control structures/regulators, and barrages to allow fish migration for propagation.
There is a need to establish formal and informal environmental education and to promote linkages between concerned institutions.
Industrial waste permit systems and inspection procedures and their effective enforcement need to be introduced.
People's awareness about fisheries and the environment has to be enhanced through proper training.
Ahmed, A.T.A, 1993. Biodiversity in aquatic environments. Assistance to Fisheries Research Institute, Mymensingh. BGD/89/012, Field Document - 3.
Ali, M.Y. 1991. Towards sustainable development: Fisheries Resources of Bangladesh. Background paper prepared for National Conservation Strategy, Bangladesh.
Bari, A. 1993. Afforestation and the nutrient sink. Assistance to the Fisheries Research Institute, Mymensingh.
Environment Policy, 1992 and Implementation programme. Ministry of Environment and Forest, Government of the People's Republic of Bangladesh.
ESCAP, 1988. Coastal environmental management plan for Bangladesh. Final Report Volume 2, Bangkok.
FAO/WB, 1989. Bangladesh fisheries sector project preparation report, Rome.
MPO, 1987. Technical report No 17. Fisheries and flood control, drainage and irrigation development.
Touch Seang Thana, Department of Fisheries, Phnom Penh.
Cage culture in Cambodia is an important economic activity on the Great Lake and Tolne Sap river.
Aquaculture in Cambodia is developing slowly as fish production from capture fisheries is still significant. Aquaculture currently contributes less than 10% of the total fisheries production in Cambodia, with inland cage culture representing 70–80% of total aquaculture production. Catfish (Pangasius hypopthalmus) and snakehead (Channa micropeltes) are the preferred species for cage culture, providing around 95% of the production from cages (74% from Pangasius sp. culture and 21% from snakehead culture). Recently, intensive shrimp culture in the coastal province of Koh Kong, near to the Thai border, increased sharply from 100 ha in 1992 to 273 ha in late 1993. Shrimp production was estimated at around 1,000–1,500 tonnes in 1993.
Although the role of aquaculture is not critical in terms of total fish production in Cambodia, environmental impacts of this sub-sector have already occured; over the last few years in inland aquaculture and over the past year in coastal aquaculture. These problems are a major concern of the present Royal Government which considers the environmental impacts of aquaculture to be a priority problem, in need of immediate attention.
Freshwater fish are produced mainly from capture fisheries, but also partially from aquaculture, and are the major source of fish for local consumption in Cambodia. Conversely, fish produced from marine fisheries and coastal aquaculture are mostly exported. Table 1 shows the total aquaculture production in Cambodia from 1988–1993.
Map of Cambodia
Table 1. Aquaculture production in Cambodia, 1988–1993.
Freshwater fisheries resources, which are crucial to fish production, have been depleted over the last few decades and decreased drastically in 1993. It was assumed by the fisheries authorities that this decrease was due to environmental degradation and illegal fishing. Aquaculture development is expected to accelerate to replace the shortfall in production, although this will be restricted by the internal and external aquaculture environment. The present (and potential) threat of environmental impacts of intensive shrimp culture development in coastal areas is a major concern of the Royal Government, who wish to find an appropriate policy for the sustainable development of this sub sector.
3. STATUS OF AQUACULTURE
3.1 Inland aquaculture
Inland aquaculture is not traditionally practised by ethnic Cambodians. Pen/cage culture systems seem to have originated in the Great Lake of Cambodia, while cage culture systems were reportedly introduced a century ago through the ethnic Chinese and later became very popular among ethnic Vietnamese. The extent of freshwater aquaculture production in Cambodia in 1993 is shown in Table 2. Official statistics (Table 3) recorded that around 89% was contributed from pen/cage and cage culture, while the rest was from pond culture. The major cultured species from pen/cage and cage systems are Pangasius hypopthalmus (73%), followed by Channa micropeltes (21%). Other species produced include Puntius sp. and Cirrhinus sp. which fishermen used to stock for a couple of months for fattening during abundant catches and then sell when fish were scarce.
Table 2. Freshwater aquaculture production, 1993.
|Great Lake||Siam Reap||Pen/Cage; Cage||0.7||1,372|
|Banteay M. Chey||-||0.004||7|
|Tonle Sap River||Kompong Chhnang||Cage||0.31||605|
Pond culture systems are mainly found in Phnom Penh city and Kandal province. There have been many efforts to develop fish pond systems in some areas with fish shortages, but the results are negligible. The fattening of Pangasilidae in ponds is very popular in the city and Kandal. This species is difficult to sell locally (or export) when fish are in abundance, so the fish lose weight and the fishermen are compelled to sell them to nearby fish farmers at a very low price. Exotic species such as carp and tilapia are not favoured by many fish farmers. Two Chinese style hatcheries produce 3–4 million seed of these species every year, but only around 50–60% of the seed were purchased by fish farmers and some aquaculture projects. The remainder were used to self-stock or devoted to the ranching programme of the Department of Fisheries.
Over the last few years, almost all of the Pangasius sp. produced were exported to Vietnam, even the captured and processed products. Similarly, snakehead were exported but since 1991, the main market has been Thailand rather than Vietnam. In 1993, the culture of sand goby (Oxyeleotris sp.) was started in the form of pond fattening, but results were not satisfactory as there was a high mortality rate (about 70%). The fish were exported live to Singapore by air. Other species mentioned in Table 3 were sold for local consumption.
The major foods used in freshwater fish culture are rice bran and trash fish (cage and pen/cage system), while dried fish is used in pond systems. Rice bran is mainly supplied by the rice mill factory, while trash fish and dried fish are from fishermen. Very often, however, trash fish is found to have been poached by the fish farmers themselves (particularly cage farmers).
Table 3. Fish production by species and system (tonnes).
(000 US $)
|Pangasius hypopthalmus *||4,222||530||380||5,132||4,155|
|Pangasius larnaudi *||20||8||28||34.6|
|Tilapia (O. niloticus)|
|Tilapia (O. mossambicus)|
|Silver carp (Hypophthalmichthys molitrix)|
|Common carp (Cyprinus carpio)||380||380||380|
|Bighead carp (Hypophthalmichthys nobilis)|
|Grass carp (Ctenopharyngodon idella)|
|Silver barb (Puntius gonionotus)|
|Sand goby (Oxyeleotris sp)*||1.5||1.5||6|
|Snakeskin gourami (Trichogaster pectoralis)*||4||4||4.8|
* Seed supply from the wild.
3.2 Coastal aquaculture
Coastal aquaculture in Cambodia was negligible before 1988, although there were a few traditional extensive shrimp farms in Kampot province. The production and value of coastal aquaculture since 1988 is shown in Table 4. Since 1989, one modern extensive shrimp farm in Koh Kong province was established, but the production recorded was very poor.
Table 4. Production of coastal aquaculture in Cambodia 1988–1993.
|Species Group||Production and Value||1988–89||1989–90||1990–91||1991–92||1992–93|
|Value (000s US $)||8||20||15||250||7,500|
|Value (000s US $)||-||-||-||-||28|
In mid 1991, intensive shrimp farming systems were introduced to Koh Kong province by Thai shrimp farmers and businessmen in the form of a clandestine joint venture with a provincial citizen. All inputs for construction and operation of the farm were imported from Thailand. Allegedly, the harvested shrimp were exported to Thailand after paying tax to the Thai customs, and the Cambodian private partner received 5% of income from the venture. Several small and mid-sized shrimp farms are owned by private Cambodian individuals. The types of shrimp culture system, location and production are shown in Table 5. Most of the shrimp farms are located at the coast, on the banks of estuaries or in mangrove forests.
Table 5. Shrimp farming systems in 1993.
|Farming System||No of Farms||Location||Area|
|Modern extensive||2||Koh Kong||10||P. monodon||5|
|6||Koh Kong||22.65||P. monodon||190|
Large (>20 ha)
|3||-||77.5||To be stocked in 1994|
Snapper and grouper cage culture was established in Dong estuary in Koh Kong province in early 1993, but collapsed during late July-August due to the impacts of freshwater runoff during heavy rainfall. Oyster culture was started in late 1993 by two farms of about 0.5 ha each. Seed was collected from subsistence fisherman and a harvestable crop is expected in mid-1994.
Although aquaculture development in both inland and coastal areas is not significant, environmental problems have been found in some areas during attempts to develop aquaculture. The Ministry of Agriculture, Forestry and Fisheries is concerned with issues related to aquaculture development and the environment in Cambodia, particularly shrimp culture. The Department of Fisheries is responsible for the administration and development in Cambodia (Table 6), although the aquaculture programme is a small one in the fisheries administration. Eight staff are engaged in the aquaculture programme of the Department of Fisheries. In addition, several international organisations and NGOs are also operating in Cambodia.
Since the sector lacks specialists and experts in Cambodia, the formulation of coastal aquaculture development plans is still in discussion at the moment. The proposal for NACA's assistance was submitted during the TAC 2 meeting in October 1993. Hopefully, the plan for development of coastal aquaculture will be formulated through co-operation between the Department of Fisheries' technically trained staff and NACA's experts very soon.
Table 6. National organisation of aquaculture development.
|Government of Cambodia|
|Department of Fisheries||Mandate|
Administration of fisheries and aquaculture at national level and development of the sector. Conservation and protection of fisheries resources.
1 administration building, Phnom Penh
1 freshwater aquaculture station
1 freshwater fish farm and seed producer
|International Organisations and Non-Governmental Organisations.|
|PADEK||Aquaculture development in S.E. Cambodia.|
|AIT||Small-scale aquaculture development in Svey Rieng province|
|SAO||Small-scale aquaculture development in Kandal province|
|SAMADHI||Cage culture development in Kampong Chhnang province.|
|UNICEF||Family fish pond in Family Food Production.|
|UNDP||Cage culture development in Great Lake, Pursat province.|
4. INTERACTIONS BETWEEN AQUACULTURE AND THE ENVIRONMENT
The environment is a relatively recent issue in Cambodia since the establishment of the Secretariat of the State of the Environment in mid 1993. Obviously, there are environmental problems (although some are not very serious) and many sectors, particularly aquaculture, have already reported that these problems restrict its development.
4.1 Impact of the external environment on aquaculture production
Impacts of the external environment on aquaculture are found mainly in cage culture systems during the dry season. There were common problems in the Tonle Sap river at Kampong Chhang town and the Mekong Delta in Kandal province. Waste water from urban areas and crowded communities along the river banks enter the water promoting nutrient enrichment and contamination. This has resulted in fish kills in cage fish farms, e.g. Pangasilidae and Cyprinidae culture systems in the Tonle Sap river, during the dry season. Wastes from fish processing plants is another water pollutant. Fish diseases (EUS) and parasite problems are found on Channa micropeltes, which grow in cages in the tributary of the Mekong Delta in Kandal province. EUS usually appears around November until February, when water recedes from the lake, while the parasite problem and water pollution occurs in the late dry season (March-May) when the tributary water becomes static and temperatures are too high.
No serious environmental problems have so far occured in the coastal area, although self-pollution by shrimp farms has occured due to over-intensification.
4.2 Contamination of aquaculture products
No contamination of aquaculture products has been reported in Cambodia.
4.3 Impacts of aquaculture on the environment
Due to the increase of fish culture in cages in inland waters, the main impact of aquaculture on the environment is probably from the indigenous feeding technology used by local farmers. This normally entails dumping large quantities of trash fish (1–3 tonnes when it is abundant) into the cages for 3–5 days to feed Pangasilidae. At many cage sites, spoiled fish is the main cause of water pollution.
The degradation of mangrove forests in coastal areas is due to the deliberate exploitation for charcoal kiln and fire wood. Existing shrimp farms, located in mangrove, also destroys the forest. The expansion of coastal shrimp farming is anticipated to be an increasingly significant issue in Cambodia.
5. INTERACTIONS BETWEEN AQUACULTURE AND THE ENVIRONMENT: IN-DEPTH STUDY
5.1 Pen/cage and cage culture in Cambodia
Pen/cage and cage culture systems are very important in Cambodian aquaculture since around 70% of production comes from these systems. Pen/cage systems are operated in the Great Lake and it is thought that this system originated in Cambodia due to the natural water system of the Great Lake. Large Pangasius hypopthalmus fingerlings are captured from the wild and stocked in pens during the dry season. When the floods begin during the rainy season, the fish are transferred to the cages. The culture cycle of Pangasius sp. lasts for two years and in the second dry season of culture the fish are transferred to pens. The fish grow up to 1.5–2.0 kg and are sold in the second flood season (August - September) after being transferred back to the cages and towed downstream to the city.
Cage culture systems are commonly operated in rivers and streams and these systems have also been reported as originating in Cambodia (Chua and Tech, 1990). Both pen/cage and cage culture systems are very popular among the ethnic Chinese and Vietnamese and at present there are around 5,000 fish farmers engaged in these sub-sectors. The value from production of these systems in 1993 was US $ 7,200,000. Pen/cage and cage culture systems are known as intensive fish culture with high stocking densities and feeding rates. The feeding strategy adopted is based on the availability of feed ingredients rather than on any scientific consideration.
5.1.2 Environmental impacts of cage culture
Environmental impacts related to pen/cage and cage culture in Cambodia are shown in Table 7. Since cage culture systems are operated in natural water bodies and the species cultured are indigenous and mainly omnivorous and carnivorous, most seed and feed input is reliant on capture fisheries. On the other hand a long running civil war for more than 20 years has resulted in poor management and under developed technical knowledge of the aquaculture sub-sector, which can lead to problems of environmental impact.
To prevent environmental impacts of cage culture, the Ministry of Agriculture, Forestry and Fisheries encouraged the Fisheries Department to conduct a survey on cage culture systems to identify constraints to development efforts and the major environmental impacts of the system. Accurate information from this survey can help the Ministry and Fisheries Department to formulate proper policies and regulations for sustainable aquaculture development, management and the conservation of natural resources.
Table 7. Environmental impacts of pen/cage and cage culture systems.
|Natural factors||Shallow and sedimented water in dry season.||1||-||-|
|No current during dry season.||2||2||2|
|External factors||Agricultural pollution (pesticides).||2||2||-|
|Urban waste pollution.||2||2||2|
|Waste from fish processing.||1||1||3|
|Pollution from spoiled feed of other cages.||3||3||-|
|Positive impacts of culture systems||Increase in fish production.||2||-||2|
|Improve economic income of riverine and lacustrine areas.||2||2||2|
|Provide employment in riverine and lacustrine areas.||3||3||-|
|Negative impacts of culture systems||Increased poaching for seed and feed.||2||3||-|
|Conflict of inland water resource use.||2||2||1|
|Self pollution and contamination of natural waters by feeding.||3||-||-|
|Key:||1 Present, but not serious.|
|2 Serious in some locations.|
|3 Widespread problem.|
6. PRIORITIES FOR DEALING WITH ENVIRONMENTAL PROBLEMS
To improve the feeding strategies for Pangasius sp. cultured in cages through extension work.
To allocate sites for cage culture development.
To select economic species which are appropriate to the cage system and the environment.
To develop pond culture, especially small-scale aquaculture, in rural areas.
To formulate low-cost fish feeds which would be available in the country to develop aquaculture.
To co-operate with other implicated institutions in the zonation of coastal areas to allocate sites for coastal aquaculture.
To organise credit systems in aquaculture development.
To monitor farming systems for sustainable development.
7. FUTURE AQUACULTURE DEVELOPMENT
Cambodian aquaculture is undeveloped due to many factors and a lack of qualified manpower, aquaculture research facilities, finance and appropriate policies and regulations are also major constraints. In the short-term for aquaculture to develop, the Ministry of Agriculture, Forestry and Fisheries and the Department of Fisheries need to have international and/or bilateral co-operation in terms of research, training of staff and farmers and the exchange of scientific information with international institutions following the requirement of the priorities listed in Section 6.
Chua, T.E. and Tech, E. 1990. Aquaculture in Asia-quo vadis?. In: M.M. Joseph (ed). Aquaculture in Asia, p 13–30. Asian Fisheries Society, Indian Branch, Mangalore, India.