sustainability of freshwater prawn farming in rice fields in southwest bangladesh

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Sustainability of Freshwater Prawn Farming in Rice Fields in SouthwestBangladeshNesar Ahmeda; Stephen T. Garnettb

a School of Environmental and Life Sciences, Charles Darwin University, Darwin, Australia b Schoolfor Environmental Research, Charles Darwin University, Darwin, Australia

Online publication date: 23 July 2010

To cite this Article Ahmed, Nesar and Garnett, Stephen T.(2010) 'Sustainability of Freshwater Prawn Farming in RiceFields in Southwest Bangladesh', Journal of Sustainable Agriculture, 34: 6, 659 — 679To link to this Article: DOI: 10.1080/10440046.2010.493397URL: http://dx.doi.org/10.1080/10440046.2010.493397

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Sustainability of Freshwater Prawn Farming inRice Fields in Southwest Bangladesh

NESAR AHMED1 and STEPHEN T. GARNETT2

1School of Environmental and Life Sciences, Charles Darwin University, Darwin, Australia2School for Environmental Research, Charles Darwin University, Darwin, Australia

Farming of the freshwater prawn (Macrobrachium rosenbergii)in rice fields is widespread in southwest Bangladesh. It plays animportant role in the economy of the country, earning foreignexchange, increasing food production and providing opportunitiesfor employment. This paper provides an overview of the sustain-ability of prawn farming in rice fields in southwest Bangladesh.It concludes that integrated prawn-fish-rice farming can helpBangladesh keep pace with current demand for fish and rice,and enhance economic development through exports of prawns.However, while prawn farming in rice fields has huge poten-tial, there are environmental consequences. Some of these mayeventually reduce productivity of the prawn–fish–rice farming sys-tem itself; others are the inevitable consequence of an expandinghuman population sequestering all available resources to itself.

KEYWORDS prawn, fish, rice, sustainability, Bangladesh

INTRODUCTION

The most important food crop for the 160 million people of Bangladesh, oneof the poorest and most densely populated countries in the world, is rice.In the 2007–2008 financial year, 29 million tons of rice was produced from

Nesar Ahmed was affiliated with the School of Environmental and Life Sciences, CharlesDarwin University, Darwin, NT 0909, Australia for postdoctoral research.

Professor Stephen T. Garnett is Director of the School for Environmental Research,Charles Darwin University, Darwin, NT 0909, Australia (E-mail: stephen.garnett@cdu.edu.au).

Address correspondence to Professor Nesar Ahmed, Department of FisheriesManagement, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh. E-mail:nesar_2000@yahoo.com.

Downloaded By: [Ahmed, Nesar] At: 03:01 24 July 2010

660 N. Ahmed and S. T. Garnett

about 10.8 million ha of rice fields (BRKB, 2009). Nevertheless, rice farmersand their families are often the poorest of the poor. Many small farmers can-not earn enough income to sustain themselves from rice production alone(WorldFish Centre, 2007). Raising of prawns and fish in rice fields offers asolution to this problem, contributing both food and income.

Bangladesh is considered one of the most suitable countries in theworld for farming of freshwater prawn (Macrobrachium rosenbergii). A sub-tropical climate and vast areas of shallow water provide ideal conditions forprawn production (Ahmed et al., 2008a). Within the last three decades prawnfarming has become one of the most important sectors in the largely agricul-tural economy of Bangladesh. Almost all prawns are exported, particularlyto the United States, Europe, and Japan (Ahmed et al., 2009). In 2007–2008,Bangladesh exported 49,317 tons of freshwater prawn and shrimp (marineand brackish water crustaceans) valued at US$445 million, of which 30% wascontributed by the prawns (DOF, 2009).

In Bangladesh, freshwater prawn farming first started in the southwestregion in the early 1970s (Mazid, 1994). A few prosperous local farmers inthe Bagerhat area began to experiment with stocking prawn in carp ponds.These innovators experimented with construction design, feeding, stocking,and other technical aspects and profited well (Rutherford, 1994). Finally afew pioneers, some time between the late 1970s and the mid-1980s, devel-oped the first prawn cultivation in rice fields in low-lying agricultural land(Kamp and Brand, 1994). In the late 1980s, a few local farmers first con-verted their rice fields into prawn farms, locally known as gher (Kendrick,1994). The Bengali term ‘gher’ is an enclosure made for prawn cultivationby modifying rice fields through building higher dikes around the field andexcavating a canal several feet deep inside the periphery to retain water dur-ing the dry season. The expansion of prawn cultivation has been dramatic,spreading since 1990 to other southwest districts such as Khulna, Satkhira,and Jessore. Since then, prawn farming in rice fields has become one of thefinancially most attractive investment opportunities in these areas (Ahmed etal., 2008a).

Prawn farming in rice fields is more significant for coastal Bangladeshthan for upland areas. The practice of small-scale prawn farming in rice fieldsis widespread in southwest Bangladesh due to the availability of wild postlar-vae (metamorphosed prawns <60 days old) and low-lying rice fields, a warmclimate, fertile soil, and cheap and abundant labor (Haroon, 1990; Ahmedet al., 2008a). Development of prawn farming has been most prominentin Bagerhat district (Figure 1), where thousands of farmers have convertedtheir rice fields to prawn farms to accommodate the profitable prawn cul-ture (Ahmed et al., 2008b). The innovation of prawn and fish farming inrice fields, combined with high prices for prawn in the international market,and rice and fish for household consumption, has led increasing numbersof farmers to convert their rice fields to prawn farms (Williams and Khan,2001; Ahmed et al., 2008c).

Sustainability of Prawn Farming in Rice Fields 661

FIGURE 1 Map of Bangladesh showing the areas where prawn farming occurs in rice fieldsand of Bagerhat district where the practice began.

However, while freshwater prawn farming in rice fields has huge poten-tial, its sustainability is affected by production technology, socioeconomiceffects, and environmental impacts. This paper reviews the constraints andsustainability of prawn farming in rice fields. Its aim is to illustrate keysocioeconomic and environmental challenges to prawn–fish–rice farmingsystems in Bangladesh.

FARMING SYSTEMS

Culture Area and Farm Size

Although the total area under prawn cultivation in Bangladesh is estimatedto be around 50,000 ha (Khondaker, 2009), there are no accurate dataon the area of prawn–rice farming. Using published sources and personalcommunications with relevant government departments, it is estimated tobe around 30,000 ha. Around 90% of the farms are located in the south-west with the remainder in the southeast region. It has been estimated that

a further 25,000 ha of the rice fields in southeast Bangladesh is suitable forprawn cultivation (Chowdhury et al., 2003).

Integrated prawn–rice farms average 0.28 ha compared with 0.60 ha forrice-only farms (Muir, 2003). Due to the increase in population, the averagesize of rice farm declined from 1.43 ha in 1961 to 0.87 ha in 1994, and isnow just 0.60 ha (Rahman and Parkinson, 2007). Prawn–rice farms were alsolarger in the past, averaging 0.35 ha more than a decade ago in Bagerhat dis-trict (Rutherford, 1994). Nevertheless, prawn–rice farms are typically smallerthan farms in the brackishwater shrimp (Peneous monodon) sector, whichaverage 4.0 ha (Muir, 2003).

Rice fields provide many opportunities for diversified production. Mostfarmers integrate prawn farming in rice fields with production of fish, rice,and vegetables. Prawns are produced for export markets while fish, rice andvegetables are for local markets and household consumption (Figure 2).

Culture Season

Rice fields provide a natural habitat for prawns during the rainy season. Theprincipal water sources for prawn farming in rice fields are rainfall, groundwater (through tube-wells), and sometimes river water through canals. Thepeak season of prawn farming in rice fields is from May to January. Prawnpostlarvae are stocked when they become available in May to June and areharvested primarily from November to January, a culture period of 6 to 9months. Fish are also stocked with prawn in May to June, but harvestedthroughout the year. The prawn culture period is limited to one crop annu-ally. However, two crop harvests are common in many countries, such asIndonesia, Malaysia, the Philippines, and Thailand (Ling et al., 1999).

Two types of rice crop are cultivated with the prawns: boro and amon.Boro rice is grown in the dry season, January to May, being transplanted

Prawn input: postlarvae, feed,

fertilizer

Integrated prawn-fish-rice

farming

Fish input: fish fry, feed,

fertilizer

Agricultural input: rice seedling,

fertilizer , crop seed

Output: prawn, fish, rice and vegetables

Household consumption: fish,

rice, vegetables

Local market: fish, rice and vegetables

Prawn: process and export to

international market

FIGURE 2 Inputs and outputs of integrated prawn-fish-rice production process.

in January-February and harvested in April-May. Amon, the main rice cropin Bangladesh, is planted during the monsoon beginning in June and har-vested in October and November. Farmers cultivate boro rice in the centralplateau of the rice field during the dry season from January to May, and themonsoon season amon rice during June to October when the prawns arein the rice field. The amon rice culture takes place either in deep water orwhile floating.

A variety of crops are grown on the dikes between the fields duringwinter (November to February) including tomato, carrot, onion, long yardbean, spinach, and pea. Potato, cucumber, ladies finger (okra), sweet gourd,and chilli are grown from April to August (Ahmed et al., 2008c). Short-cyclefruits such as banana, guava and papaya are grown on dikes throughoutthe year.

Culture Practices

Although freshwater prawn farming in rice fields is still extensive, about20% of farmers cultivate prawns semi-intensively. There are two types ofprawn farming system in rice fields: integrated and alternate (Table 1). While

TABLE 1 Types of Prawn Farming in Rice Fields in Southwest Bangladesh

Type Farmers involved Prevailing condition System response

Integratedfarming(prawn-rice inmonsoon andonly rice in dryseason)

87% • Low-lying rice field• Water availability• Fertile soil• Land scarcity

(populationgrowth)

• Labor intensive(family labor)

• Higher dikes(suitable for dikecropping)

• Intensification anddiversification

• Efficient utilizationof resources

• Increased soilfertility

• Mutual benefits ofprawn and rice

• Increasedproductivity

• Higher foodsupply (two ricecrops)

Alternate farming(prawn inmonsoon andrice in dryseason)

13% • Deeply flooded ricefield

• Saline waterintrusion

• Infertile soil• Less labor intensive• Limited capital

(lower productioncosts)

• Less modification ofland for prawnfarming

• Non-diversification• Inefficient

resource utilization• Decreased soil

fertility due tosalinity

• No competitionbetween prawnand rice

• Less production• Limited food

supply (one ricecrop)

almost all farmers cultivate boro rice in the central plateau of the rice fieldand most produce amon rice during the monsoon when the prawns are inthe rice field. However, a few farmers (13%) avoid cultivating amon ricebecause it is thought to reduce prawn growth, competing with the prawnsfor living space and placing demands on the farmers’ limited capital (Ahmedet al., 2008b). In addition, farmers believe that the use of pesticides for ricenegatively effects prawn growth. However where prawn farming has beenintegrated with rice and fish farming as happens in many Asian countriesincluding India, Thailand, and Vietnam, prawns prey on insects and improvesoil fertility (Giap et al., 2005). Nguyen (1993) noted that in integrated prawnculture in deep water rice fields, rice production has increased due to thepresence of prawns. Integrated farming is increasing in Bangladesh, partlyas a result of the promotion of integrated pest management (IPM). Also fearof damage to a high-value crop like prawns usually results in reduced useof pesticide in rice fields.

Production Systems

The annual stocking density of prawn postlarvae in rice fields is from 10,000to 30,000 per ha (Muir, 2003; Ahmed et al., 2008c). Most farmers directlystock postlarvae without rearing in nursery systems although, in recent years,a few farmers have started to use net cages as nurseries for postlarvae toimprove survival rates. Farmers generally rear postlarvae for 4 to 6 weekswith a stocking rate from 50 to 100 m−2 (Ahmed et al., 2008a).

A range of fish species are commonly cultured with the prawns in ricefields. Farmers stock Indian major carps such as catla (Catla catla), rohu(Labeo rohita), mrigal (Cirrhinus cirrhosus) and exotic carps: silver carp(Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella) andcommon carp (Cyprinus carpio). The annual stocking density of fish finger-lings (size, 5 to 10 cm) ranges from 2,000 to 5,000 ha−1. Farmers do notattempt to stock any specific ratio of different carp species (Ahmed et al.,2008c).

Supplementary feeds are used by all farmers for prawn farming in ricefields. A variety of feeds are used for prawn farming, but the preferred feedis the freshwater snail (Pila globosa). A wide variety of people, includingwomen and children, are involved in snail harvesting from the floodplains.Prawns are commonly fed 30 to 60 kg of snail meat ha−1 day−1 for a periodof 12 to 14 weeks (Chapman and Abedin, 2003). The supply of snail is vari-able, and therefore farmers also use home-made feed prepared by mixingcooked rice, rice bran, oil cake, and fish meal. Some also use industriallymanufactured pelleted feeds.

To grow-out prawns, most farmers use cow dung as organic fertilizerbecause it is relatively cheap and abundant. The purpose of using cow dung

TABLE 2 Inputs for Prawn Farming in Rice Fields in Southwest Bangladesh

Input Range Reference

Stocking (quantity ha−1 yr−1)Prawn postlarvae 10, 000–30, 000 Muir (2003)Fish fingerlings 2, 000–5, 000 Ahmed et al. (2008c)

Feeding (kg ha−1 yr−1)Snail meat 2, 730–5, 460 Chapman and Abedin (2003)Home-made feed 800–2, 500 Ahmed et al. (2008a)

Fertilization (kg ha−1 yr−1)Cow dung 562–1, 907Urea 138–741 Ahmed et al. (2008b)TSP 89–356

is to create conditions which help to increase the production of good qualitynatural feed (e.g., phytoplankton, zooplankton, periphyton, and benthos),thereby increasing prawn and fish production. The use of chemical fertil-izer is not widespread. A few more prosperous farmers combine cow dungwith varying amounts of chemical fertilizer such as urea and triple superphosphate (TSP) (Table 2).

PRODUCTIVITY

The average annual yield of prawn in rice fields has been reported as 336 kgha−1 (Muir, 2003), ranging from 250 to 450 kg ha−1 (Chapman and Abedin,2003; Ahmed et al., 2008a). A number of interdependent factors affect growthrate and productivity of prawn in rice fields, including farm size, avail-ability of water, water quality, seed and feed inputs, and other aspects offarm management. In the early 1990s, the average annual yield of prawnin rice fields was 150 to 200 kg ha−1 (Haroon and Alam, 1992). However,in the late 1990s, typical yields had increased to 200 to 250 kg ha−1 beingobtained (Rahman, 1999), probably because farmers were more confidentabout increasing stocking densities and feeding levels. Nevertheless, mostprawns in rice fields are cultivated using extensive methods, and productivityis low compared with that in other Asian countries (Table 3). Although Indiaproduces, on average, less rice per hectare than Bangladesh, the value of itsprawns is much greater; for other countries both rice and prawn productivityis higher than Bangladesh.

The average annual yield of fish with prawns in rice fields has beenestimated at 393 kg ha−1, ranging from 175 to 600 kg ha−1 (Ahmed et al.,2008b). Fish yields from rice fields depend on environment, water quality,stocking density, survival rate, the quality and quantity of feed supply, andfarm management including rice spacing. Wide spacing of rice plants (up

TABLE 3 Comparison of Prawn Yields in Rice Fields in Bangladesh and Other Asian Countries

Country Product Yield (kg ha−1 yr−1) Reference

Bangladesh Prawn 250–450 Chapman andAbedin (2003)

Rice 1, 050–4, 200China Prawn 300–450 Weimin and

Xianping (2002)Rice 3, 500–5, 000

India Prawn 785–2, 133 Nair et al. (2002)Rice 1, 500–2, 000

Thailand Prawn 816–1, 268 Giap et al. (2005)Rice 3, 360–3, 556

Vietnam Prawn 286–518 My-Lan (2006)Rice 4, 300–4, 700

to 25×25 cm) allows more light to penetrate underwater, which in turnincreases aquatic primary production and thus the availability of natural feedfor fish (Mustow, 2002). The size of fish at stocking, the duration of culture,and the size at which the fish are harvested also influence total yield.

The average annual rice productivity has been estimated at 2,352 kgha−1, ranging from 1,050 to 4,200 kg ha−1 (Ahmed et al., 2008b). Total riceproduction has probably decreased as a result of widespread conversionof rice fields to prawn farms. However, at the farm level, many farmersreported increased rice production as a result of higher dike construction,which keeps fully saline water out of their fields (Ahmed et al., 2008c).Measures of rice productivity include the area of canal and water for prawnfarming, and thus actual yield per hectare of rice alone is likely to be 20%to 25% higher. The global average rice yield is around 4,000 kg ha−1 crop−1

(Frei and Becker, 2005).Although production costs have increased to an average of US$1,343

ha−1 yr−1, prawn farming in rice fields is almost always profitable, netreturns averaging US$1,430 ha−1 yr−1, ranging from US$1,306 to US$1,887ha−1 yr−1 (excluding vegetable cropping). Of this, prawn production makesup an average of 69% of total return, with that of fish and rice productionbeing 14% and 17%, respectively (Ahmed et al., 2008b). Because the variouscrops are harvested at different times of the year, household cash flow isimproved and the risk of crop damage from flooding reduced.

PRODUCTION CONSTRAINTS

A number of constraints are reported for prawn farming in rice fields, includ-ing high production costs, insufficient supply of prawn postlarvae, shortage

TABLE 4 Common Constraints for Prawn Farming in Rice Fields in SouthwestBangladesh

Constraint Element

1. High production costs • Increased seed, feed and labor costs• Disposing of household assets• Loan

2. Lack of prawn postlarvae • Limited hatchery production• Poor quality of hatchery postlarvae• Inadequate supply of wild postlarvae

3. Inadequate supply of snail • Excessive snail harvesting• Snail population has declined• Negative environmental impacts

4. Prawn diseases • Black spot, white spot and gill disease• Poor water quality• Organic wastes deoxygenation

5. Climatic conditions • Flood• Drought• Saline water intrusion

6. Social conflicts • Friction between rich and poorfarmers

• Poaching of prawn• Poisoning prawn farms

of snails for food supplementation, water pollution, diseases, flood, drought,saline water intrusion, and social conflicts (Table 4).

High Production Costs

Costs of prawn farming in rice fields have increased significantly in recentyears as a result of increased labor wage rates. To begin producing prawns,farmers need a large amount of money for converting rice fields into prawnfarms. Construction costs are linked closely to labor costs and depend onfarm size, location, number of laborers required and season. The prices ofboth postlarvae and feed have also increased significantly since prawn farm-ing has become widespread (Ahmed et al., 2008b). The main problem forfarmers is the shortage of operating capital. Inadequate finance can there-fore be a significant constraint for resource-poor farmers wishing to startprawn farming in rice fields. Farmers primarily obtain finance by dispos-ing of household assets, such as cows, gold jewellery and timber. Severalinstitutions including banks, non-governmental organizations and local mon-eylenders have begun providing credit to farmers in recent years. Althoughmost farmers are able to pay their loans within the first 1 to 2 years, a fewfarmers sometimes have harvest failures due to flood, outbreak of disease

or other unavoidable reasons, and as a result they can fall into a continuingcycle of debt.

Lack of Prawn Postlarvae

The expansion of prawn farming in rice fields depends on availability ofpostlarvae. Traditionally, farmers prefer to stock wild postlarvae rather thanhatchery-produced stock, because the production of hatchery postlarvaehas been limited and farmers consider them to be of lower quality. Thesurvival of wild postlarvae is reported to be much higher than that ofhatchery-produced stock. However, catches of wild postlarvae have declinedin recent years because of over fishing, use of destructive gear and envi-ronmental degradation. Indiscriminate fishing of wild postlarvae with highlevels of bycatch has negative impacts on biodiversity in coastal ecosys-tems (Ahmed et al., 2010). This concern has provoked the imposition ofrestrictions on postlarvae collection. Nevertheless, wild postlarvae demandhas increased in recent years due to expansion of prawn farming, while thesupply of postlarvae has declined. Although there are 81 freshwater prawnhatcheries in Bangladesh, only 38 (47%) are effectively operational. Togetherthey produce around 100 million postlarvae annually, 20% of total demand(Ahmed et al., 2008a). Lack of technical knowledge, inadequate skilled man-power and insufficient wild broodstock are important reasons for the poorproductivity of many hatcheries.

Inadequate Supply of Snail

Farmers reported higher prawn yields and lower production costs fromfeeding snails rather than home-made or other feed. However snails haveeffectively become extinct in most prawn farming areas due to excessiveharvesting during the monsoon, their peak reproductive season (Ahmed etal., 2008a). As a result, snails are now harvested from neighboring districts.Over-harvesting of snails has had other deleterious effects. Large quantitiesof discarded snail shells have polluted and blocked of canals and otheropen water bodies which are then not used for fishing, hinder fish migra-tion and foster proliferation of mosquitoes. Loss of the snails may also causean increase in the growth of at least some species of aquatic macrophytes(Gain, 1998), reducing light penetration and leading to eutrophication ofwater bodies.

Prawn Diseases

Disease is a major problem of prawn farming in rice fields. A wide variety ofdiseases can be found, including shell diseases or black spot, white spot, and

gill disease (MacRae et al., 2002). Black spot, the most widespread disease ofprawn from postlarvae to harvest size, is caused by bacteria and sometimes,later, by fungi (Cai et al., 1997), causing mortality and also reducing thevalue of harvested prawns through discoloration. Environmental factors suchas poor water quality and the presence of toxins are key causes. Howeverthe few farmers in Bangladesh who periodically exchange water or drainout waste water during harvest do so into canals which flow on to adjacentwasteland. The high levels of organic matter in this waste deoxygenatesthe water, killing prawns, fish, and other aquatic life. Prawn diseases canthreaten the viability of the prawn marketing sector (i.e., poor supply dueto crop failure).

Climatic Conditions

Prawn farming in rice fields is at high risk from flood and drought (Williamset al., 2004). The production of prawns in rice fields is closely linked to thebehavior of the monsoon with an excess of water during the wet seasonand practically no water during the dry season. As Bangladesh is a verylow-lying country, any rise in sea level and siltation in the channels of theGanges River delta can exacerbate the effects of annual floods in south-west Bangladesh causing saline water intrusion into prawn farms. Suddenor prolonged floods and cyclones often damage prawn-rice farms. Cyclonesoriginating in the deep Indian Ocean track through the Bay of Bengal wherethe shallow waters contribute to huge tidal surges when cyclones makelandfall. A cyclone in 1970 resulted to deaths of around 300,000 people,and another in 1991 led to the loss of 138,000 lives (World Bank, 2000).In November 2007 tropical cyclone Sidr, the most severe to hit Bangladeshin 10 years affected more than 8.7 million people, killing over 3,000 anddamaging more than 890,000 ha of crops and prawn farms (United Nations,2007). In May 2008, cyclone Nargis devastated coastal life in Bangladesh. InMay 2009, after cyclone Bijli veered away from the southern coast a monthearlier, cyclone Aila hit southwest Bangladesh, leaving hundreds of thou-sands of people homeless and killing at least 100 people (Ahmed et al.,2010). Large areas were still affected a year later.

Social Conflicts

A number of social conflicts have accompanied the prawn sector inBangladesh (Bundell and Maybin, 1996; Ito, 2004). Low levels of socialcapital are both cause and consequence of the vulnerability of the poor.In prawn-rice farming areas, better-off farmers and wealthy people haveforced poor farmers to sell their farms. Friction between the two sides hassometimes led to scuffles involving villagers and hired enforcers employed

by the wealthy. The minority of Hindu people also feel insecure due toconflict with Muslims, and a number have migrated to India, especially toWest Bengal. Losses can also occur when jealous people throw poison intofarms at night, after which all the prawns may die, and poaching of prawnsis also a common problem (Ahmed et al., 2008c). Because theft is rampant,many farmers provide a small thatched shelter, perched on the dike, wherea night guard can be stationed, and some better-off farmers recruit guards toprotect against theft and poisoning. Theft risks usually increase when prawnfarms are too far from farmers’ homes to allow surveillance. Thieves whoare caught have sometimes been beaten by community people, others havebeen handed over to the police.

SUSTAINABILITY

Sustainable Aquaculture: A Conceptual Framework

The term ‘sustainability’ refers to the ability of an ecosystem or any suchon-going system to continue functioning into the indefinite future with-out declining through overloading the principal resources on which thatsystem depends (Frankic and Hershner, 2003). Sustainability can only beattained when environmental conditions are appropriate and maintained,and this includes ecological, socio-anthropological and economic aspects ofenvironment. Therefore, any activity or practice should include the follow-ing general steps for sustainable resource management: 1) environmentalresource assessment, 2) environmental impact assessment, 3) policy frame-work and regulatory measures, 4) socio-cultural and economic assessment,5) implementation, and 6) monitoring and evaluation (Frankic and Hershner,2001). In assessing the sustainability of any system, consideration should begiven to at least the following:

● the long-term continuity of production;● financial viability;● social impact and equity;● environmental impact; and● efficiency of conversion of resources into useful product.

Sustainable development is the management and conservation of thenatural resource base and the orientation of technological and institutionalchange in such a manner as to ensure the attainment and continued sat-isfaction of human needs for present and future generations (FAO, 1995).Such sustainable development (in the agriculture, forestry or fisheries sec-tors) conserves land, water, plant and animal resources, is environmentallynon-degrading, technically appropriate, economically viable and socially

acceptable. Sustainable development improves people’s quality of life withinthe context of the earth’s carrying capacity (Girardet, 1992).

In establishing ‘sustainable aquaculture’ it is essential to maintain abalance between the need for aquaculture development and the need fornatural resources conservation. In this context, it is necessary to recognizeand deal with increasing competition for resources (Frankic and Hershner,2003). The sustainable development of aquaculture requires adequate con-sideration of interactions among environmental, social and economic factors(Chua, 1992; Caffey et al., 1998; World Bank, 1998). Concerns includethe quantity of land, water and energy used, and effluents produced(Boyd, 1999), on–going demand, market share, and profitability as well asemployment opportunities and social benefits (Tisdell, 1999; Wurts, 2000).

Thus, sustainability of prawn farming in rice fields in southwestBangladesh can be expressed in terms of three interrelated aspects: 1) pro-duction technology, 2) socioeconomic aspects, and 3) environmental aspects(Figure 3).

Production Systems

Prawn farming in rice fields is a form of integrated aquaculture-agriculture(IAA). Ideally IAA results in increased income diversification, intensification,improved natural resource efficiency, increased productivity and sustainabil-ity (Lightfoot et al., 1992; Prein, 2002). According to Nhan et al. (2007), IAA isparticularly appropriate for resource-poor farmers, maximizing benefit from

Sustainability of prawn-fish-rice farming

Socioeconomic

Production technology

Environment

FIGURE 3 The three inter-related aspects of the sustainability of prawn-fish-rice farming.

their labor. In a country like Bangladesh, where land is scarce and the pop-ulation is growing rapidly, IAA makes the most of scarce resources (Frei andBecker, 2005), particularly since there are often synergistic benefits betweenthe different enterprises (Lightfoot et al., 1993; Prein, 2002).

In the production system employed the rice provides shelter to theprawns and keeps the water temperature at optimal levels in the hot sum-mer months. Prawn and fish wastes increase the amount of organic materialin rice fields, thus farmers need less fertilizer. According to Lightfoot etal. (1992), rice yields have increased in integrated culture because of thefertilizing effect from the fish droppings, which greatly increases nutrientavailability to the rice crop. Interactions among prawn, fish, rice, and veg-etables also help small-scale farmers lower production costs because weeds,insects and pests are consumed by the prawns and fish (Fernando, 1993;WorldFish Centre, 2007). There is thus less use of insecticides and pesti-cides, as prawn and fish can play a significant role in controlling many peststhrough IPM (Williams et al., 2004).

The sustainability of the production systems used in prawn–fish–riceaquaculture in Bangladesh relates primarily to their productivity comparedto that of other countries. The Bangladeshi systems are characterized by theirrelatively low, though increasing, productivity as well as their low inputsfrom external sources. Thus, while production per hectare may be lower,this analysis does not include the global footprint of the production system.In Bangladesh, the global footprint includes the capture of wild postlarvaeand snail with some food additives and cow dung. This footprint is enlargedby the inputs into transport from farm to point of sale. Systems in developedcountries, however, are likely to include larger inputs of chemical fertilizerand fossil-fuel driven technology (Gliessman, 2006; Hazell and Pachauri,2006). Such systems are more vulnerable to changes in oil price and arelikely to be less sustainable overall due to their larger footprint beyond thefarm boundaries.

Furthermore comparisons in productivity are currently only possi-ble for rice and prawn production. Fish and vegetables production mustalso be included. Again this analysis must include external inputs. InBangladesh, farmers must divide their labor between the four differentproducts—prawns, fish, rice, and vegetables—as well as fulfilling othersocial responsibilities. Time is therefore likely to be a constraint on produc-tivity. Elsewhere automation may reduce the time constraints on individualfarmers, so result in increased productivity, but at the expense of socio-ecological sustainability elsewhere and of employment locally. Thus, beforethe sustainability of the production systems can be compared, lifetime anal-ysis of the global footprint for each type of product derived from the systemneeds to be conducted. Given the likely results of this analysis, the sustain-ability of the prawn–fish–rice production system in Bangladesh is likely tobe relatively high.

Socioeconomic Aspects

In southwest Bangladesh, prawn farming in rice fields is now widelypractised and socially accepted by the farmers. Integrated prawn–fish–ricefarming has been simple for small-scale farmers to adopt, and is proven tocontribute to enhanced and diversified food production as well as incomegeneration. The increase in income results from production of prawns as anexport product. Income from rice, fish, vegetables, and fruits are additionalto the income from prawns.

Before prawn farming a large number of farmers lived below thepoverty line. After converting their rice fields to prawn farms, they haveincreased their social status and food consumption. Households of farmersare able to eat rice three times a day and also eat better quality food, suchas fish, meat, milk, eggs, fruit, and vegetables (Ahmed et al., 2008c). Theconsumption of fish has increased notably over recent years because of theincreased supply from integrated prawn–fish–rice farming. Households offarmers tend to eat small fish rather than sell them. These are a valuablesource of micronutrients, vitamins and minerals. Similarly, although farmersnever eat the prawn meat itself, prawn heads and legs supplement proteinintake during the prawn exporting season. Most farmers have also improvedthe quality of their housing, health and sanitary facilities, and drinking watersupply through tube-wells. There have also been an increased number ofrecreational items, such as radios and televisions, and mobile phones forcommunication (i.e., prawn marketing).

Prawn farming in rice fields also offers diverse livelihood opportunitiesfor the rural poor. A range of associated groups such as wild postlarvae col-lectors and traders, snail harvesters and traders, feed traders, intermediaries,prawn traders, transporters, and day laborers (including women and chil-dren) have benefited (Ahmed et al., 2008a). A network for seed, feed andfertilizer trading, and prawn marketing has been established. The oppor-tunities for day laborers to find work have increased significantly. Laboris required for construction of prawn farms, night guards, input market-ing, snail breaking, prawn harvesting and marketing, and processing plants.From a variety of published sources and personal communications with rel-evant government departments, it is estimated that around 600,000 peopleare directly involved in prawn-fish-rice farming and associated activities inaddition to 400,000 people engaged in prawn and shrimp postlarvae fishing.

Prawn farming in rice fields has implications for the economic sus-tainability of Bangladeshi farming systems. Integrated prawn culture isinfluenced at a macro level by world trade, national development goals andgovernment policy while, at a micro level increasing efficiency in resourceallocation within existing prawn-fish-rice farming will benefit developmentof future prawn industry enterprises. The global trends in intensifica-tion, population growth, economic growth and technical development will

probably flow through to Bangladesh with benefits to overall efficiency inthe sector.

Around the world, sustainable aquaculture has revitalized rural commu-nities where sustainable economic development is often difficult (Davenportet al., 2003; Jana and Webster, 2003). In such communities, however, theintroduction of aquaculture into areas traditionally used largely for commer-cial fisheries and a variety of recreational activities has sometimes resultedin conflict. There is no evidence of this happening in Bangladesh. Althoughsome conflict has arisen as a result of the expansion of prawn–fish–ricefarming, the consequences seem minor compared to the broader benefits.Overall the introduction of prawns into the production system seems to havehad positive benefits for social sustainability.

Environmental Aspects

Prawn farming in rice fields in southwest Bangladesh has not been associ-ated with any of the negative environmental consequences for which marineshrimp production has received so much criticism. However, in recent yearsthere are some concerns about its long-term environmental sustainability.Unplanned conversion of rice fields to prawn farms may have negativeimpacts on water quality. Construction of farms back-to-back and side-to-side raises worries about water quality control and disease. There is alsoover-harvesting of snails for use as prawn feed and the wild stock of prawnshas also decreased due to uncontrolled fishing of prawn postlarvae (Ahmedet al., 2008b). Several aquatic plants and weeds have completely disappearedbecause of prawn farming in rice fields (Karim, 2006), and fewer cattle arereared for want of grazing land. Aquatic birds and ducks are also chasedfrom the prawn farms and have no other habitat.

Some of these environmental impacts may eventually reduce the pro-ductivity of the industry itself. The reduction in prawn fry and snail must beaddressed if the production is to be sustained let alone expanded. The lossof alternative production systems, such as cattle and of biodiversity, includ-ing plants and birds, has broader implications for the sustainability of thesystem. Essentially their loss represents a simplification of the system and areduction of redundancy, thus reducing its overall resilience—its capacity towithstand shocks. It is the inevitable result of the expanding human pop-ulation sequestering an increasing proportion of available resources. Theirloss effectively indicates that, even with the increasing productivity, this canonly be a temporary palliative solution to the underlying problem of anexpanding human population.

Nevertheless, in spite of these environmental problems, the practice ofprawn farming in rice fields has had a range of positive socioeconomic,environmental and technological impacts (Figure 4).

• Foreign exchange earning • Increased income • Higher food consumption • Employment opportunities • Improved social status • Reduced vulnerability

Socioeconomic impacts

• IAA farming systems • Eco-friendly • Diversification • Efficient resource use • Increased productivity • Cost effective

Production system Environmental impacts

• Integrated pest management • Reduced pesticide use • Increased soil fertility • Decreased fertilizer use • Reduced salinity intrusion • Controlled disease

Integrated prawn-fish-rice farming

FIGURE 4 Production system, socioeconomic and environmental benefits of the addition ofprawn farming to rice-fish production systems in Bangladesh.

CONCLUSIONS

Freshwater prawn farming in rice fields plays an important role in theeconomy of Bangladesh, earning valuable foreign exchange, contributing toincreased food production, diversifying the economy and increasing employ-ment opportunities. Prawn farming in rice fields appears initially to havebroad potential in terms of sustainability, based on the concept of pro-duction continuing indefinitely at present levels in the existing locations.Nevertheless, a number of factors contribute to the vulnerability of poorfarmers including high production costs, inadequate supply of prawn post-larvae and snail, diseases of prawns, flood, drought, and social problems.In addition, farmers may not be achieving the highest levels of productiv-ity because of the lack of technological capacity and the use of extensiveculture methods. While increased technology and improved managementskills may increase productivity, changes to the production system need tobe tempered by analysis of the full range of off-site impacts and on-site ben-efits from the existing system. However, expanding the number of prawnhatcheries and low-cost locally produced ingredients for feed other thansnail would help to increase production, reduce the negative environmentalimpacts, and increase job opportunities.

The irredeemable effects of increased intensification of food produc-tion from rice fields are loss of biodiversity. The trade-off, however, ifthe food demand for 140 million people in Bangladesh is to be met, isto acknowledge that the intensification of land use in existing agricultural

systems is preferable to the conversion of the small area of remainingnatural ecosystems for agricultural purposes. Since adoption of integratedprawn–fish–rice farming beyond the seasonal floodplains of southwest andsoutheast Bangladesh is likely to result in marginal increases in productiv-ity because rice production systems differ, it will be necessary to increasethe productivity of those parts of the seasonal floodplains not already usingan integrated production system. If prawn, and fish, farming in rice fieldsexpand to one-third of the 2.83 million ha of floodplains, the country willearn an additional US$335 million foreign exchange from prawn alone(Wahab et al., 2008). Eventually rice and fish production would also increase.

Integrated prawn–fish–rice farming can help Bangladesh keep pacewith the current demand for food through fish and rice production, andeconomic development through export oriented prawn production. Thisintegration can maximize the productivity of the land and water resources ofBangladesh. While not entirely sustainable, the losses in biodiversity appearto be an inevitable and unavoidable price to pay for the expanding humanpopulation.

ACKNOWLEDGMENTS

This study was a part of the first author’s postdoctoral research at the Schoolof Environmental and Life Sciences, Charles Darwin University, Australia.The study was supported through the Australian Government EndeavorResearch Fellowship. The opinions expressed herein are those of the authorsand do not necessarily reflect the views of Endeavor Fellowship Program.

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sustainability of freshwater prawn farming in rice fields in southwest bangladesh

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