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4

A REVIEW OF THE DEVELOPMENT OF INTEGRATED IRRIGATION AQUACULTURE (IIA), WITH SPECIAL REFERENCE TO WEST AFRICA

Cécile Brugère
Fisheries and Aquaculture Department
FAO, Rome, Italy

Brugère, C. 2006. A review of the development of integrated irrigation aquaculture (IIA), with special reference to West Africa. In M. Halwart & A.A. van Dam, eds. Integrated irrigation and aquaculture in West Africa: concepts, practices and potential, pp. 27–60. Rome, FAO. 181 pp.

Abstract

A review of the literature available on integrated irrigation aquaculture (IIA) activities in 13 countries of West Africa is presented. The concept of IIA has been the subject of some publications emphasizing the 'theoretical' potential and advantages of the practice. Other studies have tended to assess separately irrigation and aquaculture development/potential in these countries and have focussed on the technical aspects of each activity. Inland valley bottoms, floodplains and full-control irrigation systems have been identified as key environments to support the integration of irrigation and aquaculture. Background information is provided on the context and justification for the integration of irrigation and aquaculture activities, and specific IIA activities are detailed for each key environment based on documented case studies in West Africa. Issues identified as positively or negatively affecting the potential for integration include health concerns linked to the incidence of water-borne diseases, pest and weed management, wastewater recycling, mitigation of land salinisation, conservation of wetlands, demand for fish, marketing and processing, optimal allocation and pricing of irrigation water. It is emphasized that assessments of IIA potential should fully incorporate socio-economic and cultural factors as these deeply influence the ultimate adoption of new technologies. Despite a number of technical and socio-economic challenges to overcome, IIA activities should make a positive contribution to the livelihoods of operators and farmers, provided that they are given opportunities for private initiatives and that technologies are adapted to their needs.

Introduction

The preparation of this document was commissioned by the Inland Water Resources and Aquaculture Service of the FAO to serve as working paper for the FAO-WARDA Regional Workshop on Integrated Irrigation Aquaculture in Bamako, Mali, 4–7 November 2003. The geographical focus of the review is West Africa and includes Burkina Faso, Mali, Niger, Nigeria, Senegal, Ghana, Chad, Côte d'Ivoire as well as country members of the WARDA Inland Valley Consortium (IVC): Benin, Cameroon, Togo, Sierra Leone and Guinea.

The investigation of integrated irrigation-aquaculture development focuses on three key areas equipped for irrigation: inland valley bottoms, floodplains, full control irrigation systems, and includes rice-fish farming activities. IIA activities are reviewed in each key environment in West Africa, assessing potential, constraints, opportunities and other issues related to the future development of integrated irrigation-aquaculture in Africa and presenting recommendations on how to proceed with IIA development in each country and the region as a whole.

The first section of the document provides background information and rationale for developing IIA. Section 2 describes the key environments, aquaculture and irrigation systems covered by the study and includes case studies on integrated irrigation aquaculture activities carried out in floodplains, inland valley bottoms and full control irrigation systems in the countries under review. Other issues related to the development of IIA, such as health concerns, weed control, wastewater recycling, land salinisation, conservation of wetlands and irrigation water pricing are addressed in a third section. Challenges and opportunities for future integration are discussed in a fourth section in the light of the above information. The last section summarizes the findings and concludes.

Background and rationale for IIA

Irrigation: issues of water scarcity and water productivity

When 70 percent of the world's supplies of developed water areused by irrigation and overall withdrawals are forecast to increase, growing scarcity and competition for water adds a new dimension to the food security debate (Seckler et al., 1998). Problems related to irrigation are low water use efficiency, expensive exploitation of new water resources, resource degradation through water-logging, pollution and salinisation, which have a negative impact on drinking water supplies and health, and subsidies and distorted incentives which lead to further depletion and unequal benefits (Rosegrant, 1995). In the face of these challenges and to ensure increased food production and stable prices in forthcoming decades, investments and policy reforms have to be undertaken to improve water and irrigation management (Rosegrant and Cai, 2001).

Seckler et al. (1998) have classified countries according to calculated threat of water scarcity. None of the countries under study belonged to the group of currently water-scarce countries. However, Niger, Cameroon, Côte d'Ivoire, Nigeria, Ghana, Benin, Chad and Burkina Faso were classified as Group 2 countriesin which conditions are often unfavourable for crop production and which must develop more than twice the amount of water they currently use to meet reasonable future needs. In these countries, it was recommended to put emphasis on expanding small-scale irrigation and supplemental irrigation to increase the productivity of rainfed agriculture. In Group 3,countries were Guinea, Senegal and Mali1, which need to increase their withdrawals by an average 48 percent to meet their water needs.

In the context of integrated uses, water productivity, i.e. the amount of food produced per unit volume of water used, is more informative than irrigation efficiency, the amount of water required for an intended purpose divided by total amount of water diverted to a spatial domain of interest (Guerra et al., 1998; Molden, 1997). As costs of developing new water resources increase, increasing productivity of existing resources, both irrigation and rainwater, becomes more attractive and can be achieved in four ways (Seckler et al., 1998):

A fifth way to increase water productivity is through the integration of a non-consumptive use of water (fish farming) within existing irrigation sources.

Aquaculture

Aquaculture is the fastest growing food producing industry in the world (FAO 2000a). Beyond some negative environmental impacts (usually specific to intensive marine or coastal aquaculture) inland fish farming has the potential to positively contribute to the livelihoods and food security of the poor (Ahmed and Lorica, 2002; Edwards, 2000; Halwart et al., 2003) and the emphasis is now on aquaculture for development, instead of solely aquaculture development (Friend and Funge-Smith, 2002). Living aquatic resources are however in a period of transition and face issues related to efficiency, in particular in post-harvest operations, equity, management, intensification and policy formulation (Williams, 1996). Improved water management satisfying both agriculture and aquatic resources can be a way by which water uses are optimised and local livelihoods enhanced but it calls for integrated policies that recognize the multiple uses of inland water bodies and the complexity of livelihoods to promote their sustainability.

Integrated farming systems

The concept of integrating fish production with other activities (crops, poultry, livestock) as part of complex farming systems is not new and its advantages have long been recognized (Pullin and Shehadeh, 1980; Little and Muir, 1987; FAO/ICLARM/IIRR, 2001). From a poverty reduction perspective, these systems contribute to improved livelihood outcomes through diversification of food production and household activities, income increases, nutrition improvements and spread of risk and uncertainty (FAO, 2000b; Prein, 2002). From an environmental perspective, they contribute to sustainable natural resource management through recycling/reuse of resources and nutrients, environment-friendly pest management, increased land and water use efficiency and waste management (ibid.).

While contribution of irrigation and aquaculture development to alleviating poverty have been separately assessed (Hussain and Biltonen, 2001 and Chambers, 1988 in the case of irrigation; Friend and Funge-Smith, 2002 and Edwards, 2000 in the case of aquaculture), the integration of both activities is relatively new, especially in Africa. Despite being referred to as a “drought-prone area”, sub-Saharan Africa has under-exploited irrigation resources and infrastructures which would benefit from rehabilitation and modernisation (Alam, 1991) as well as from integrated approaches to water management to accommodate both irrigation and aquaculture.

Integration of irrigation and aquaculture

Much of the current literature recognizes the “theoretical”potential of the integration of irrigation and aquaculture. This potential is based on separate assessments of irrigation and aquaculture activities and potential for further development. While integrated systems such as rice-fish farming or cage culture in human-made (irrigation) reservoirs have been thoroughly studied, technical aspects of IIA in canals and management issues related to multiple water uses have been documented in very few studies (e.g. Li, 2002; Ingram et al., 2000).According to Fernando and Halwart (2000), harvesting fish in irrigation systems is a practice dating back at least two millennia. Although seldom recorded, it seems to have been widespread in the tropics and subtropics, especially in irrigated rice fields. Irrigation systems using stored or diverted water have increased exponentially over the past 50 years, but fish farming within these irrigated systems has not expanded equally and there is now a huge potential for this integrated enterprise (Fernando and Halwart,2000).

Integrated irrigation-aquaculture is one aspect of the integration of agriculture and aquaculture. It is the practice of two technologies associated in the aim of increasing productivity per unit of water used. In the case of simultaneous irrigated rice and fish production, integration can be partial or complete depending on the spatial location of irrigation and aquaculture units: fish can be raised in a pond upstream or downstream of the paddy field, but also within the paddy field. In the case of irrigation conveyance systems, fish can also be raised in cages located in canals (Li et al., 2005; Ingram et al., 2000; Haylor, 1994). Other possible systems are detailed in the next section.

IIA presents a number of generic advantages, most of which stem from the benefits of integrated farming systems. Positive environmental impacts include (after Kabré 2000):

At the household level, positive impacts include enhanced food security, balanced nutrition and increased incomes (Moehl et al., 2001) through the production of a commodity (fish) readily available at times of necessity and the provision of supplementary irrigation for crops in the dry season (Little and Muir, 1987). Increases in income for the landless poor were also shown to be possible with the adoption of fish (Indian Major Carps) cages in irrigation canals (Brugère, 2003).

While the integration of aquaculture in irrigation systems is receiving increasing attention, technical constraints and opposition to the integration have hampered its development in some areas. In the case of large-scale reservoirs, cage/pen aquaculture can limit or alter the value of water in multiple uses by altering flow regimes, scenic value, disrupting spawning, interfering with navigation, preventing access and polluting water, especially when reservoirs are used as potable water supply (Haylor, 1994; Beveridge, 1987). In irrigation supply canals, cages, especially when fouled, can represent a barrier to flow and have encountered some opposition to their use (Costa-Pierce and Effendi, 1988 in the case of Indonesia; Jauncey and Stewart, 1987 in the case of Egypt). In addition, the integration of fish production in an irrigation scheme creates an extra burden on management, calling for a balance between the needs and constraints of fish and crop production (Li et al., 2005; Haylor, 1994).

Key environments and IIA development in West Africa

It is necessary to determine which irrigation environments and which aquaculture systems are suitable for integration. Table 1 links each FAO-defined key environment (inland valley bottoms, floodplains and full control irrigation systems) and related water-engineered/ irrigation systems to the aquaculture systems they can potentially support, as suggested by Haylor (1994). The following section reports case study analyses of such integration, with their potential and constraints, in West Africa.

IIA development in West Africa

Because of the specific focus of this study on integrated irrigation aquaculture, reviews of irrigation and aquaculture sectors at national levels are not reiterated. They have however been summarized in a table, which also includes potential of integrated irrigation-aquaculture by country, evaluated from feasibility studies and information from other sources (Annex 1).

Not many examples of practical initiatives have been reported in the context of West Africa and some aquaculture case studies do not mention the environment in which they took place. A notable exception is rice-fish integration. Following the FAO workshop for an African network on integrated irrigation and aquaculture (Moehl et al., 2001), case studies were carried out in Mali (Bamba and Kienta, 2000), Côte d'Ivoire (Coulibaly, 2000), and Burkina Faso (Kabré, 2000). These studies are amongst the most thorough studies available on IIA activities (usually trials or past activities) in Africa and describe the technical characteristics as well as some economic and social impacts of the systems developed. Sectorial approaches to development of each activity still prevail among practitioners and policy makers. Mention is rarely made of “integrated approaches” to management of irrigation water, taking into account other water uses, in particular fish production (fisheries or aquaculture) and domestic uses.

Floodplains

Floodplains play a fundamental role in supporting large human populations. Many activities they support depend on their hydrology (Thompson and Polet, 2000). The promotion of their management for fish production by extensive aquaculture techniques (e.g. ponds dug into the floodplain, dams which block drainage channels and dikes enclosing areas) is not new (Welcomme, 1976).

Floodplain resource use is usually synchronized with annual flood cycles as in the Hadejia-Nguru wetlands of North-eastern Nigeria (Thompson and Polet, 2000) where rice is cultivated in inundated areas, which are then planted with other crops after the floods recede. Fishing and cattle grazing intensity also varies with rising and falling water levels. The location of rice cultivation and small-scale irrigation is determined by water availability in the wet and dry seasons.

Rice-fish
In the Mopti region of Mali, rice-fish farming in the floodplain of the Niger River (Tiroguel area) was assessed in a case study analysis of a potential project (Bamba and Kienta, 2000). It was estimated that the project would benefit from the Special Programme on Food Security (SPFS) to allow floodplain dwellers to legally catch fish naturally caught in the floodplain irrigation network and enhance fish production in the irrigated floodplain area destined to deepwater rice cultivation. With the rehabilitation of a small-scale, community-managed irrigation area, a pond area of 10 ha would be created in the middle of a deepwater rice area of 13 ha. Water in the irrigated zone would accommodate both fish and rice simultaneously: a hole would be dug in the middle of the pond for fish to survive after drainage for the rice harvest. Management of both pond and rice would rely on involvement of all community members and harmonisation of management interests. Tilapias and Clarias spp. would be stocked in the pond using natural populations entering the floodplain and additional stocking. Fish feed will be made from organic fertilizers (on-farm waste recycling).

The financial analysis of this integration based on a number of production targets suggested positive net returns. Of all the impacts envisaged, nine could be positive, five negative, six potentially negative and two negligible. Benefits would relate to increases in social capital (community cohesion through communal management of rice and fish production), transfer of resource management from the state to stakeholders, increased autonomy in decision-making, timely supply of fish when resources decline in the delta, with increased incomes for producers, in particular women, and improved diet.

Table 1: Key environments, water-engineered systems and aquaculture systems.

Key environment (as defined in FAOSTAT)Water engineered - systems (after Haylor, 1994)Status of fisheries (capture and enhanced) and aquaculture (after Haylor, 1994)Aquaculture systems with potential for integration
Full control irrigation systems (large scale)Large reservoirs (dams) for storage/flood controlLarge and increasing portion of fish production in many countries but only a recent innovation in Africa, in particular regarding reservoir-based aquaculture1Cages/pens
Irrigation supply canalsFish entering the system and self-sustaining populations are important in Asia. Stocked fish are used to control growth of aquatic plants and disease vectors.Cages/pens (e.g. carp polyculture in China)
Water dispersion (drainage and waste water)No capture fishery. Aquaculture used to produce useful biomass from a controlled aquatic medium and treat wastewater.Ponds, small reservoirs
Water transfer systems (conveyance schemes)Fisheries not widely reported.Cages/pens
Full control irrigation systems (small scale)Farm sub-systems (= rice fields)Capture fishery is as old as rice culture with yields around 135–175 kg/ha2. Fish culture provides higher yields but this varies with field conditions.Rice-fish (e.g. fingerling production in China)
Small-scale reservoirs (= farm dams, dual purpose reservoirs, tanks or irrigation reservoirs) for rain and flood water storageCombination of fishery and aquaculture practices.Cages/pens, rice-fish, coves within impoundments (e.g. fingerling production in China)
Groundwater irrigation (well, borehole, pump)Extensive aquaculture in open wells but risk of conflict with other uses (human/ livestock consumption) 3.Fish stocked in wells3
On-farm reservoirs or pondsExtensive to semi-intensive aquaculture 4Cages/pens, ponds
Inland valley bottoms / wetlandsSmall-scale dammed reservoirsFish entering the system and self-sustained populations 5Cages/pens, ponds
Rice fieldsFish entering the system, sometimes stocked 5Rice-fish
Floodplains, including flood recession areasSmall-scale dammed reservoirsFish entering the system and self-sustained populations 6,7Cages/pens, ponds
Rice fieldsFish entering the system, sometimes stocked 5,7Rice-fish

1 Beveridge and Phillips (1987), ICLARM and GTZ (1991);
2 Hora and Pillay (1962), Ali (1990);
3 Institute of Aquaculture (1998);
4 Little and Muir (1987);
5 Coulibaly (2000);
6 Welcomme (1976);
7 Bamba and Kienta (2000).

Constraints to overcome would be linked to lack of institutional support and the single purpose management of water for irrigated rice areas, lack of funds for aquaculture activities in general, perception of aquaculture as a secondary activity by farmers, lack of water availability outside areas equipped for full control irrigation. Nevertheless, the potential for rice-fish integration was considered high and with adequate policy support, the example of the Tiroguel area could be extended to all deepwater rice areas, ponds and inland valley bottoms of Mali.

In Burkina Faso, examples of direct rice-fish integration (fish growing in the paddy field) in the Kou Valley and indirect integration (fish pond upstream of paddy field) in the Bragué irrigation scheme were assessed (Kabré, 2000). The Kou Valley is a floodplain equipped for gravity irrigation while the Bragué irrigation scheme supplies water from canals linked to the Bragué dam reservoir. Despite partial success, the Kou Valley trial is more informative than the Bragué case study, which brings little insight into IIA (fish production was a secondary use of the pond, originally designed as a supplementary source of irrigation for rice; farmers did not participate in fish rearing and fish was not harvested). In the Kou Valley trial (1987–1988), rice plots were individually supplied by an irrigation canal. Sluices were fitted with grids to prevent stocked and wild fish populations to mix. A pond, constructed amidst the scheme to nurse tilapia fingerlings and fertilized with organic and mineral inputs, was communally managed by a group of fishers. A number of difficulties were faced in the set up and management of the operation: farmers were sceptical and fishers showed interest instead, conflicts arose over water allocation in the irrigated perimeter and a flash flood interrupted a second trial unexpectedly. In addition, the financial impact of the integrated activity on households' budget was limited and in-depth analysis showed that rice-fish farming was significantly determined by the availability of sufficient labour force in the household.

Other constraints to the widespread development of the activity, evaluated by Kabré and Zerbo (2001), are linked to the lack of direction from the government's Fisheries development agency and from research institutes in terms of aquaculture development and rice-fish culture in particular, lack of fingerlings, competition for feed resources, and lack of funds, land and water for IIA. However, during the trial, farmers started to recognize benefits of the integration of fish in paddy fields or in a pond used to irrigate paddy. It is estimated that their attitude could be easily changed by extension efforts and awareness raising on nutrient recycling, technical knowledge on IIA management and some forms of co-operative saving to fund and develop new IIA activities. This would be supported by the existing demand for fish and the possibility for post-harvest activities (e.g. fish smoking) involving women.

Ponds
In Nigeria, the development of a fish pond in the floodplain of the Hadejia-Ngura Wetlands was reported in Thomas (1994). This study highlighted a common characteristic of many aquaculture projects in Africa: the failure to consider economic and social aspects to ensure the success of technical developments. The project purpose was to increase fish production from seasonal ponds to compensate for decreases in capture fisheries. Techniques used involved deepening ponds and controlling the outflow of water after flood recession, fertilizing with cow manure, and increasing the natural fish density with wild-caught fingerlings of Clarias lazera and tilapia (Sarotherodon galilaeus). The depression chosen was a community pond and thus was community-managed. A nearby pond was left unmanaged and used as control. Fingerlings were provided by fishers and manure collected from camps of Fulani (nomadic pastoralists).

Thirteen kg of fish were harvested from the unmanaged pond after 4 months and 35 kg were harvested from the managed pond after 8 months. However, economic analysis of the trial showed lower returns to labour in the case of the managed pond (5.19 Naira per person-hour) compared to the unmanaged pond (6.04 Naira per person-hour), although labour surpluses available in the dry season at the time of fish harvest and possibility to sell fish in the “lean” period could offset the lower returns.

Despite encouraging results, community participation and technology adoption were low because of the following factors:

Inland valley bottoms

Rice-fish
Oswald et al. (1996) showed positive interactions and returns from the combination of fish farming (mainly Oreochromis niloticus) carried out in ponds adjacent to lowland rice fields in peri-urban zones of Côte d'Ivoire. The activity was a suitable farm diversification strategy and benefited from the proximity of markets.

In Senegal, the rice-fish farming potential was assessed in the Senegal River valley (north of the country) and in inland valley bottoms and floodplains (south in the Casamance area) (Sanni, 2002). In the Senegal River valley, rice is intensively farmed and water managed to suit its growth requirements (including periods of low water or dry land) which would limit the growth of fish stocked in rice plots. However, potential is higher in the Casamance area where rice is grown extensively and some form of rice-fish integration already exists and could be easily improved. Despite farmers' interest in IIA, in particular rice-fish, and existing irrigation management knowledge, high demand for fresh fish in remote inland areas, fry and fingerlings availability, a number of constraints have been noted.

Some of these constraints are common to IIA activities in general as practised elsewhere (see also contributions by Peterson et al., this volume). Local environment (e.g. proximity to the Delta where fish is plentiful) and ethnic origin were also considered as influencing factors in the potential of IIA. While these analyses showed potential, Sanni (2002) acknowledged the need for socio-economic assessments to be carried out, in particular in the context of intensive rice-fish farming in the Senegal River valley.

Full control irrigation systems

Dams/reservoirs
Diallo (1995) reported encouraging results from the semi-intensive rearing of Tilapia guineensis and Sarotherodon melanotheron in pens in dammed valleys of Casamance, Senegal, as a method to cover the gap of protein demand after habitat loss and diminution of catches.

In Kainji Lake, Nigeria, an experiment was carried out using six wooden-framed, poultry mesh cages measuring 1 m3 stocked with specimens of Tilapia galilaea, T. zillii and Oreochromis niloticus together and T. galilaea separately (Ita, 1976). The cages were suspended from nylon ropes into the water and the ropes tied to the float of a landing pier a few meters from Kainji Dam. Fish were fed daily with pellets prepared by mixing dried fish, roasted or fresh groundnuts, guinea-corn bran, yam flour and commercial vitamin premix or blood meal together. Results showed that growth of T. galilaea over 164 days was higher than in the case of polyculture over 171 days. Improving cage design to reduce feed wastage and cost of construction were suggested to improve the economic viability of the operation.

Canals
In Senegal, Sanni (2002) assessed the potential of several forms of IIA. In primary canals, trials were unsuccessful because of theft, bird predation, and lack of participation by target group but showed some potential. Low depth and easy predation constituted constraints in secondary and tertiary canals. Large-scale reservoirs located within irrigation systems offered the most potential for fish to be intensively grown in cages. Drainage areas were not suitable because of the presence of harmful pesticides in the water.

Rice-fish
In Côte d'Ivoire, a case study analysis of IIA (rice-fish) trials was carried out in the valley bottom village of Luenoufla in the Daloa region (Coulibaly, 2000). The trials, initially set up under the Projet Piscicole Centre Ouest (PPCO) in 1992, were followed up by the APDRA-CI (Association Pisciculture et Développement Rural en Afrique tropicale humide - Côte d'Ivoire) and have shown positive results. Areas where rice-fish cultivation was carried out are usually cascade systems, with rice plots upstream and downstream of a small dammed reservoir where fish were grown. A nursing pond was built as part of the irrigation system, which was also designed to accommodate organic dike cropping (vegetables) and cattle drinking. Polyculture of tilapia, Hemichromis fasciatus, Heterotis niloticus and grass carp (Ctenopharyngodon idella) was practised.

In economic terms, it was shown that the fish activity contributed to 20 percent of the total value of production (rice, vegetables and maize) and increased the value of the valley bottom equipped for irrigation. However, returns to labour were lower than returns to the land. Benefits at the household level included changes in decision-making regarding land exploitation, with a switch from upland cultivation to irrigated valley bottom exploitation, increased returns to labour compared to rice farming only, improved diet, increases in subsistence consumption, household budgeting with income from fish buffering against larger expenses, and more independence for women through dike cropping and aquaculture post-harvest activities. At the village level, increased year-round human activity around the reservoir was a sign of overall improved water management. In addition, employment creation, strengthening of social and human capital (group collaboration, women's involvement) along with market opportunities for fresh fish were other positive impacts of the project.

Rice-fish culture trials were conducted on test plots in a large irrigation scheme in the Upper East Region of Ghana (Kumah et al., 1996). Two different systems, both with refuge ponds on one side of the rice field, were evaluated. One had a lateral trench around the entire rice field. The other had only a single central trench. After 105 days, rice yields ranged from 1.6 to 4.1 tonnes per hectare. Lateral trenches prevented rat infestation of the rice crop, thereby increasing yields. Over the same period, fish production ranged from 133 to 142 kg per hectare. Results encouraged farmers to embark on trials on their own irrigation plots.

Issues and benefits related to IIA development

Issues raised in this section are not specific to West Africa, although, reference to countries under review was made when possible. Experiences from other areas can however inform the development process of IIA in the region. The list of examples is not exhaustive but rather meant to illustrate the issues.

Human health issues

There are various strands to the debate on health-related issues in the development of aquaculture in tropical countries. Some argue that water retention in ponds or other water bodies destined for aquaculture increases the incidence of water-borne diseases (West, 1996). Others say that larvivorous and mollusci-vorous fishes stocked in fish ponds and other water bodies, in combination with other agents, can be used as biological controls and increase fish production (Chiotha, 1995; Fletcher et al., 1993).

The development of fish farming in inland water bodies constructed for the activity can be accompanied by a surge in water-borne diseases. Fish ponds have been found to host higher numbers of bilharzia snails than the streams and canals that feed them, in particular when these ponds have weedy edges, increasing the risk of infection (Chiotha and Jenya, 1991). Similar findings were reported in Slootweg et al. (1993) in Cameroon where the introduction of irrigation (work in irrigated paddy and creation of permanent water reservoirs near the village) increased exposure to schistosomiasis. The situation was similar in the area of the Weija reservoir in Ghana, where the combination of environmental (proliferation of water weeds, changes in flow rates of water) and social (migration of infected farmers and fishers, flawed resettlement programmes) had contributed to increased incidence of schistosomiasis (Ampofo and Zuta, 1995).

However, the introduction of aquaculture offers an alternative approach in dealing with a vector-borne disease problem created by the construction of irrigation works (Slootweg, 1991; example of Cameroon). Selecting appropriate fish species, such as Trematocranus anaphyrmis, T. placodon and Astotilapia callistera, which are molluscivorous fish, could serve the dual purpose of controlling snail vectors of bilharzia and increasing pond productivity through occupation of empty niches (Chiotha, 1995). Similarly for malaria, Fletcher et al. (1992) showed that stocking an indigenous cyprinodontid fish, Aphanius dispar, in all types of water storage containers in Assab in Ethiopia, was a successful and well-accepted method to control mosquito larvae, with monthly stocking necessary to maintain adequate levels of control. In an assessment on the role of fish as biocontrol agents, Halwart (2001) concluded that well-maintained aquaculture operations did not increase but rather contributed, often significantly, to the quality and diversity of the ecosystem.

It is also often pointed out that organochlorine insecticides, in particular DDT and HCT, used to control mosquito populations and to contain the spread of other diseases, have accumulated in trophic chains and the environment (D'Amato et al., 2002) and have increased water pollution, making it potentially unsuitable for aquaculture (Dua et al., 1996). Aquaculture development was hampered in the irrigation canals of the Gezira Scheme (Sudan) because of the use of harmful insecticides, larvicides and molluscicides and the lack of co-ordinated administrative and technical measures to cope with pollution in these canals (George, 1976). The presence of pollutants, especially pesticides leaching from fields into irrigation and drainage channels can have negative impacts of pesticides on fish growth, although methods are available to minimize them (Haylor, 1994). Aerial application of insecticides to control blackflies (transmitting onchocerciasis or river blindness) in heavily infected areas and water bodies did not have significant impacts on fish and aquatic invertebrate populations (Biney et al., 1994; FAO, 1996).

Pest, disease and weed control

The uncontrolled proliferation of aquatic weeds (Salvinia molesta and Eichhorna crassipes) in African irrigation systems and waterways has been a growing concern but adapted management of these plants could benefit fish stocks in inland waters and be used in aquaculture (Petr, 1992). In the South Chad and Baga irrigation projects, in Nigeria, where aquatic weeds were spreading in canals and drains, the introduction of herbivorous fish such as grass carp (Ctenopharyngodon idella) was considered a suitable biological alternative to expensive weed control treatments, while increasing overall fish production (Okafor, 1986). However, preference should generally be given to the use of indigenous fish species before the introduction of an alien species is considered.

In rice-fish systems, fewer agricultural pests, reduced incidence of weeds or less damage caused by pests and diseases in the presence of fish is reported (Halwart, 2001). However, it has also been reported that some fish species damaged rice plants in the floodplain of the central delta of the Niger in Mali (Matthes, 1978). While few fish were found to attack rice predominantly for food (Tilapia zillii, Alestes spp. and Distichodus spp.), other species (e.g. O. niloticus) only attacked rice when other foods were scarce, or damaged plants during other activities (e.g. Heterotis and Clarias). This can however be reverted by using local varieties (e.g. Oryza glaberrima) or deepwater, late-flowering “floating rice” varieties (Matthes, 1978). In addition, periphyton on rice stems can be a significant source of fish food and the nibbling of fish on the rice stems is sometimes mistakenly interpreted as feeding on the rice plant itself (M. Halwart, personal communication, 2003).

Wastewater management

Wastewater management and recycling should be taken into account when aiming to increase water productivity. Aquaculture both produces and transforms waste, and as such, widens the scope of IIA by encompassing environmental and multiple water use considerations.

Wastewater recycling
Wastewater stabilisation ponds can be used simultaneously to polish the treatment of municipal wastewater (Metcalfe, 1995) and support fish production. Nutrient-rich effluents from wastewater fish ponds were then shown to be suitable for irrigation applications (Shereif et al., 1995) and sludges from oxidation ponds for land fertilization (Hosetti and Frost, 1995). Aquaculture in wastewater ponds contributes to eutrophication and water quality control while providing direct economic benefits through the sale of fish (Yan and Zhang, 1994). Health risks associated with the utilisation of wastewater for fish production have been extensively documented and all studies concur in recognizing fish produced in municipal (Slabbert et al., 1989) and mixed domestic/industrial (Sandbank and Nupen, 1984) effluents and from primary and secondary treated wastewater (Khalil and Hussein, 1997) as microbiologically safe for consumption.

Waste-fed ponds
Integrated fish pond systems are often a means to recycle otherwise wasted nutrients through the use of pond sediments and water to fertilize and irrigate adjacent crops (Little and Muir, 1987). Animal waste is extensively used to fertilize fish ponds throughout Asia as part of integrated livestock-fish (pig, duck, cow, chicken) systems (ibid; Edwards and Little, 2003; Yan et al., 1998). Fish pond water used to irrigate vegetable plots in South Africa has been shown to increase yields (Prinsloo and Schoonbee, 1987). Whilst these examples focused on fish pond water irrigation, Prinsloo et al. 's (2000) water efficiency assessment used effluents from a fish pond in combination with micro and flood irrigation technologies. They showed that nutrient-enriched water use efficiency was higher when applied with the former (drum-drip irrigation) to vegetables and maize than with flood irrigation. This illustrates how the gap between water-saving irrigation technologies (e.g. micro-irrigation) and IIA technology, which a-priori, could not be carried out without flood/irrigation water storage devises, could be bridged.

In the floodplains of West Africa, which have been shown to be deficient in essential crop nutrients (N, P and K) (Buri et al., 1999), the use of effluents from aquaculture operations could be used to “fertigate” crops in dry seasons (Valencia et al. 2001, example of forage crops in the U.S. Virgin Islands). According to Edwards (1998), the best prospect for the implementation of wastewater aquaculture systems is in arid and semi-arid countries where there is increasing pressure to reuse water.

Mitigation of land salinisation

Salinisation is one of the many problems faced by irrigation systems around the world and is partly caused by an excessive use of water (Agnew and Anderson, 1992). In West-Africa, salt-related soil degradation due to irrigation activities is a major threat to the sustainability of rice cropping under semi-arid conditions (van Asten et al., 2003). Using saline water for irrigation affects yields but measures to rehabilitate saline land or reduce irrigation water salinity levels are often too costly for smallholders. When combined with water logging and overall lack of water availability to irrigate, this leads to poorer lands left uncultivated (J. Gowing, personal communication, 2003).

However, enhancing food production will necessitate the conversion of marginal lands to other appropriate land uses with technologies increasing nutrient use efficiency through integrated nutrient management and recycling mechanisms as well as improving water use efficiency through the development and adoption of water harvesting, recycling and irrigation (Lal, 2000). It has been suggested that the opportunity cost of digging an on-farm reservoir (or pond) on cultivable land was lower than using the same land for agricultural purposes (Brugere and Little, 1999). Opportunity cost of saline uncultivated land would be a fortiori lower. This concurs to support that productivity of degraded areas by salinity could be enhanced through stocking of salt-resistant freshwater species in ponds and use pond water to irrigate crops with higher salt resistance (e.g. sorghum, groundnut, pearl millets). In Egypt, reclaimed salt-affected land was taken under cultivation with continuous flooding and fish production and later converted to rice culture (Halwart, 1998).

Conservation and sustainable use of wetlands

Wetlands across the world provide a wide range of valuable functions and benefits but are threatened by over-exploitation and unwise developments, the most important being dam construction and equipment of wetlands for intensive modern irrigation (Hollis et al., 1988). There is growing evidence that large-scale irrigation schemes are often less efficient than traditional extensive systems supporting cropping, grazing and fishing activities, as shown in the comparison of water productivity in the natural floodplain of the Niger inner delta and the irrigated rice scheme of the Office du Niger in Mali (Drijver and Marchand, 1985; cited in Hollis et al., 1988). It is therefore possible that the extensively equipped wetlands may provide a more adapted environment for the development of adapted small-scale IIA activities, which should also be in tune with principles of wetland conservation and sustainable use, as defined in the Ramsar Convention.

Demand, markets and fish processing

Processing and marketing aspects of a commodity to be produced in larger quantities are significant factors in the success and development of IIA activities. In Burkina Faso, where dried fish is frequently added to meal preparations, changes in diet composition have been reported, with a switch from traditional to marketed products (Lykke et al., 2002). This suggests that fish products, in particular from aquaculture, should keep up with raising demand for transformed products with post-harvest value added (the bulk of small-scale aquaculture production in Africa is sold fresh, in contrast to capture fisheries which are subjected to post-harvest transformation such as smoking, roasting, or drying (Chimatiro, 1998). However, such transformations are the cause of health hazards as no handling standards are in place or enforced (ibid.) and species such as catfish may not be protected from dermestid beetles solely through sun-drying (Lal and Sastawa, 1996).

Improvements in processing infrastructure was shown to improve the handling, marketing and development of demand for fish products in Ghana (Mensah, 1990). In addition, the role of the private sector in fish processing and of women as marketing agents of aquaculture production should be emphasized (Jaffee, 1995; Gladwin, 1980). This would be particularly important in the promotion and take off of IIA and the creation of a sustained demand for fish. However, Hecht and de Moor (undated) stressed that the findings of past and location-specific fish marketing and preference studies should not be interpreted as applicable to the whole of sub-Saharan Africa and that consumers' preferences should be investigated where aquaculture is promoted, and farming practices and species choices be modified accordingly.

Optimal allocation and pricing of irrigation water

A distinction has to be made between optimal use and allocation of water among users, based on socio-economic trade-off analysis - to which IIA belong and water pricing, a policy instrument for demand management and cost recovery (Hellegers, 2002). Another distinction relates to efficient allocation and optimal allocation (ibid.), as reflected in the two core, yet antagonistic, principles of water management: efficiency, i.e. the amount of wealth generated by a given resource, and equity, the fairness of allocation across economically disparate groups (Dinar et al. undated). Irrigation water is a special case because, in comparison with alternative uses, it has high opportunity costs, and yet, the ability to pay for irrigation water is limited, particularly in resource-poor agriculture and irrigation-dependent areas (Hellegers, 2002).

Demand-led approaches have been advocated to provide households with the water provision services they want and are willing to pay for (Whittington et al., 1998). Charging for quantities of irrigation water has been envisaged in irrigation management (World Bank, 2003), with advocacy for a shift from charges per area of land under irrigation, to charges per volume of water used (Rosegrant, 1997; Rosegrant and Perez, 1997). This process is however faced with difficulties in terms of implementation, enforcement, user acceptance as well as overall legitimacy in developing countries (Molle, 2001; Perry, 2001), especially as fisheries and aquaculture activities tend not to be taken into account in future water demand and management scenarios (see Rosegrant et al., 2002; Rosegrant and Ringler, 1999). The status of fisheries and aquaculture as non-water consumers would indeed complicate charging issues further.

Challenges for future IIA development

Haylor (1994: 92) suggests that: “in order to assess situation specific feasibility, it is necessary to quantify how appropriate it is to integrate the principal objectives of fish production with the primary objective of each system (e.g. water conveyancing in irrigation supply canals). Consideration should be given to the major characteristics of the system, costs and benefits of integration, to the type of fish species that might be appropriate, the potential fish producers (operators) and the scale of investment.” However, achieving this will not be without overcoming a number of challenges.

Technical challenges

There are more technical challenges to overcome for the integration of irrigation and aquaculture in the case of full-control, engineered irrigation systems because of the lack of flexibility in the management of these systems, in particular if large-scale. Water supply reliability is a crucial constraint to integration of aquaculture because of the slow response of long supply canals to operational adjustments, variations in rainfall across extensive command areas and poor communications between operation staff resulting in difficulties to co-ordinate management actions to ensure adequate water provision to sustain fish populations. In addition, the reliability of conditions suitable for aquaculture depends on design and operation decisions that influence continuity of supply and/or storage.

When cages are used in irrigation canals, engineering aspects such as velocity inside cages and its impact on fish growth, drag forces and impacts on canal flow, impact on canal conveyance capacity and operational performance and possible interference with maintenance activities should also be taken into account. Adapted cage designs to prevalent hydraulic conditions is likely to be necessary (Li et al., 2005). Morphology and slope of canals will influence cage site selection.

In principle, the provision of secondary storage should reduce water inequity between head and tail sections of irrigation systems (Brugere and Lingard, 2003), whilst providing opportunities for aquaculture development in comparison to large-scale irrigation systems without storage (Li et al., 2005). However, this will only be achieved if operating procedures reduce rapid fluctuations in water storage, as were observed in Sri Lanka, as this does not increase irrigation efficiency and constitutes a serious barrier to integrating fish farming in storage structures (Gowing et al., 2004). Even to satisfy non-consumptive uses of water, multi-purpose management is complex and difficult. Efficiency and equity goals are often irreconcilable. Aquaculture adds a further variable into the equation (Brugere, 2002).

Which IIA technologies to promote and where?

Emphasis should be placed on IIA development in small-scale irrigation systems as they require minor modifications to incorporate fish production. These modifications can be undertaken by farmers themselves and are more easily sustained than important large-scale changes (Haylor, 1994). In this context, rice-fish farming in inland valley bottoms and floodplains appears to be the most easily and readily achievable activity. Construction of fish ponds in inland valley bottoms, floodplains and full-control irrigation systems, may also be relatively easy, although by requiring more substantial investments and land transformations, it may be out of the reach of individual, resource-limited farmers. Large-scale irrigation systems present a high “theoretical” potential, with the advantage of being accessible to those without land. However, promoting the integration of aquaculture in such systems will require collaborations between user groups and water managing institutions (fisheries and irrigation authorities) to ensure the multi-purpose management of water, as well as improvements in the aquaculture technology.

Technology adoption

Technology adoption revolves around the assessment of two distinct, yet related, issues. The first is who to target as a suitable group to ensure the long-term success and spread of the activity. The second is why some interventions are adopted, while others are not. Paris (2002), in reviewing the reasons for the success and failure of improved integrated crop-animal technologies, underlined the paucity of information related to the socio-economic impacts of such interventions on rural communities. Her reasons for low adoption can also be applied to aquaculture:

To these have to be added local knowledge and water availability constraints, as well as in the context of Africa, the legacy of previous aquaculture experiences, national economic situations, marketing channels, households' perceptions of scarcity and security, and forms of land tenure and security of tenure, in particular for women (Harrison, 1991). Others, typically associated with all types of fish farming, e.g. fish mortality and escapees, high feed costs, poaching of cages, distance from the water body, lack of co-operation among family members or groups of aquaculturists, have contributed to disinterest and abandonment of fish culture (Bulcock and Brugere, 2000).

Tackling only technical constraints may be insufficient as adoption rates are also explained by the characteristics of the decision-making unit and the actors (belonging to the household or not) involved (Solano et al., 2001). Low interest and adoption of aquaculture technology may result from inadequate consideration or neglect of women's role in household decision-making and income generation as well as technology poorly adapted to their needs and quickly appropriated by men (Suwanrangsi, 2001).

For ponds constructed in full-control irrigation systems in Zambia and Tanzania, Van der Mheen (1999) suggested a method to analyse and monitor farmers' perceptions and criteria of adoption of the activity. While physical and environmental criteria influenced participation and uptake, other factors linked to the pursuit of the activity (household labour availability, inputs, information), innovation adoption (relative advantage, compatibility, complexity, triability and observability) and farmers' needs (for protein, diversification and flexible water allocation) were paramount in the success of the IIA. He showed that suitable conditions increased adoption rates but that unfavourable topography did not affect participation as much as often assumed: farmers constructed ponds even on steep slopes. However, the compatibility of fish farming in irrigation schemes subject to water shortages, the complexity of the technology and the difficulty to try the activity independently and on a small-scale restricted the integration of ponds in water distribution systems and lead to a preference for independent fish ponds. Adoption rates increased in areas where at least two of the assessed needs (protein, diversification and flexible water allocation) were moderately or strongly felt by farmers and their households. From farmers' point of view, benefits brought about by an independent source of water outweighed benefits in the form of fish and income. However, this attitude should not be seen as impeding the development of aquaculture in irrigation structures, as fish still provide a “plus” to households. As with “saving pond fish for emergencies” rather than increasing pond productivity (Harrison 1991), long-term technology uptake will have more chances of succeeding when farmers decide which technology they would like to use, regardless of its productivity compared to other activities (Brummett and Noble, 1995).

Socio-economic challenges

Many socio-economic challenges are linked to the making the right decisions, at the outset of initiatives, on who to target with the activity. As mentioned above, this is also a key determinant of future adoption rates. These decisions are however confounded by political choices and their implications at macro levels, in particular in relation national development priorities and policies a country wishes to put in place.

Who to target?

The very poor or the wealthier?
The aim of increasing water productivity may only be partially achieved if its benefits are not shared by the very poor or other disadvantaged groups. However, targeting aquaculture development efforts to the poorest has been questioned (A. Coche, personal communication, 2003; Hecht, 2002; Wijkstrom, 2001). This does not mean that the poorest are to be excluded from aquaculture and irrigation development processes as they may initially benefit indirectly through increased and cheaper fish supply. But the high costs of irrigation development, even small-scale, and high risk associated with some IIA technologies (e.g. fish cages in canals) may make IIA initially unattractive to poorer groups (Brugere, 2003). However, as the technology is improved and adapted to local irrigation systems, and its cost reduces over time with wider uptake by wealthier households, it will become an alternative activity to the resource-poor, provided their access to the necessary irrigation structures and aquaculture inputs is ensured.

Landless or landowners?
Large-scale irrigation schemes serve only a minority of the world's farmers (Haylor, 1994). The accessibility of large-scale irrigation schemes is a serious constraint for the landless poor people to participate in aquaculture activities. Although the extent of landlessness may not be as important in Africa as it is in other parts of the world (A. Coche, personal communication 2003), the premise of rice-fish culture is that rice fields are available, excluding the landless from the activity. Similar constraints apply to fish pond construction with the additional requirement of accessing and affording a source of water (e.g. pumps or wells). These limitations, which do not apply in the same way to large-scale irrigation systems, which the landless can access and use for other purposes than irrigation, reduce the potential of aquaculture as an entry point for poverty alleviation amongst this group.

Men or women?
So far, most aquaculture and irrigation development have targeted men, disguising the fact that women play a considerable role in the management of both activities, in particular small-scale aquaculture for home consumption (Harrison, 1991). Targeting men or women has implications for training as extension agents are usually males (ibid.). Working with women may result in the quicker adoption of a new activity where the nonchalance of men may slow down the process, as shown during the implementation of South-South co-operation of the Special Programme for Food Security in Senegal (FAO, 2002c).

Table 2. Trade-offs in development of aquaculture within irrigation systems (Brugere, 2003).

Dry season water supply / livelihoods improvementsversusGroundwater depletion (environmental damage)
Rainfed crops adapted to water shortages and grown for subsistenceversusIrrigated cash crops for exports and national income
Adoption of aquaculture by richer households and targeting aquaculture to areas where support networks exist, i.e. promoting 'commercial'-scale aquacultureversusNarrowing of gap between rich and poor, creating opportunities for the poorest of the poor, i.e. sustaining the "poverty focus" of international development
Provision of assistance (subsidies)versusEntrepreneurship incentives (credit)
Fish production for local markets and improved nutritionversusValue-adding activities and higher prices for urban dwellers

Fishing or land-based households?
Traditional aquaculture development has focused on crop farmers and land-based operations such as fish ponds. Fishers may be closer to “hunter-gatherers” and have unique attributes that require careful consideration if they are targeted by aquaculture activities in irrigation reservoirs for example (Balarin et al., 1998). If aquaculture, and in particular integrated irrigation aquaculture, is recognized as a branch of farming and not fishing activities, this also has implications for extension as in sub-Saharan Africa, most programmes rely on agents with capture fisheries background and little knowledge of farming systems (Harrison, 1991).

Micro or macro-priorities?
With the promotion of any form of integrated irrigation-aquaculture, decision-makers will be faced with a policy dilemma. At the micro-level, the first challenge is to address the usual lack of coincidence of all necessary resources, such as water, land, and labour availability, in particular for poorer households. The second challenge relates to the contribution of the activity to improved incomes, nutrition and well-being. At the macro-level, donors and governments alike will be faced with difficult trade-offs and choices related to prioritization of interventions at the grass root level and implementation of policy instruments at the national level (Table 2). Aquaculture in irrigation systems can be an attractive activity and priority for poverty alleviation. But overcoming the trade-offs involved in its promotion will be crucial in improving water use efficiency and equity and successfully reducing the vulnerability of the rural poor. Much ultimately depends on governments and development agencies' decisions.

Conclusion

Summary of findings

Potential for the integration of irrigation and aquaculture exists throughout West Africa. Many of the constraints identified are common to all countries and are usually linked to limitations in the development of either irrigation or aquaculture. They are ranked hereafter by decreasing order of importance, according to their frequency of mention in Annex 1:

  1. Lack of extension/technical support - conflict/competition over (water) resources;
  2. Low credit availability;
  3. Lack of information - government support/direction - high irrigation development costs - presence of pesticides in waterways - unfavourable climatic/hydrographic conditions - socio-economic factors;
  4. Lack of fingerlings and fish feed;
  5. Lack of aquaculture and rice-fish farming experience - lack of funding from international donors.

Some issues, each affecting positively or negatively the potential for IIA development in Africa, were reviewed. Health concerns arising from water-borne diseases in irrigation systems could be limited by the right combination of fish species used as bio-control agents of disease vectors. Assessments of the presence of pollutants in water sources used for irrigation should be carried out prior the introduction of aquaculture. Positive impacts of fish raised in paddy fields outweigh negative ones. The design of fields can be changed relatively easily to accommodate and retain fish stocks including the use of a pond upstream or downstream of the field for aquaculture. Wastewater can be used for both irrigation and aquaculture after minor treatment. This may be a suitable option in more urban areas (water for gardens and fish production).

The human and environmental impacts associated with dam building have slowed down the pace of irrigation development through large irrigation schemes, which may constitute a constraint to the potential for IIA. Priority is given to the rehabilitation of existing schemes or enhancement of small-scale ones (Alam, 1991), which are in fact more suitable for the implementation of integrated irrigation aquaculture activities and wetland conservation principles.

Marketing and processing of cultured fish production is an area deserving attention to ensure the safe handling of fish for consumers' safety and the maintenance or enhancement of benefits drawn from those involved in post-harvest activities, i.e. women, as fish production and market supply increase. Deserving as much attention, from a broader perspective, is the issue of irrigation water pricing which could become even more complex with the introduction of a non-consumptive, yet water-dependent, activity and which could slow down the adoption and promotion of IIA by national governments.

Opportunities for the development of IIA activities thus exist but are country-specific. In general, they appear to prevail in small-scale, community or farmer-managed irrigation (existing or rehabilitated) which offer the flexibility required for multi-purpose water management and favour local stakeholders' participation. The relative technical simplicity of rice-fish farming and the familiarity of most farmers with rice, irrigation and wild fish populations are strengths to build on. This type of integration could present an advantage over more complex integrated systems such as fish cages in canals, which require higher technical inputs and are risky ventures.

It is important however that, from a research perspective, no IIA options be left out while others are promoted in priority based solely on “simplicity” criteria as many other factors influence the success of technical interventions. Among these factors are social, cultural and economic dimensions. Most of the case studies showed that lack of consideration given to either of these dimensions resulted in failure, results below expectations or low technology adoption. Although limited, a search of the literature has provided an insight into technical aspects linked to the field implementation of IIA activities. The socio-economic impacts of the activity, where it has been tested, have however been scarcely studied or reported. Bearing in mind that the sum of (irrigation+aquaculture) potential does not equal integrated irrigation-aquaculture potential, more research is needed to cover these issues, along with livelihood impacts, technology adoption, gender and marketing aspects related to the introduction of IIA.

Concluding comments

Replicating lessons and experiences from Asia has not always proved successful on the African continent with its cultural diversity and environmental specificities. Moving from donor-driven aquaculture development to private, individual interventions based on farmers' initiatives and resources will help avoid activity planning on false assumptions of labour and resource availability, production for home consumption and easiness of fish farming (FAO, 2000b). With more flexibility and time given for changes and farmers' initiatives to take place, sustainability and adoption of IIA activities may be more successful than past aquaculture development projects.

However, IIA should not be seen as an entirely new paradigm. It has been happening “naturally”, in simpler forms (a pond naturally retaining a few fish, used to water the garden), in many parts of Africa and in the world at large. If objectives are set for developing and strengthening the activity, they should initially focus on the consolidation of the knowledge-base on integrated aquaculture and irrigation. This is more important in terms of technology adoption than, for example, a larger number of ponds or higher fish production figures, as it will contribute to the outlasting of the activity after departure of donor assistance (Harrison, 1991).

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Appendix 1. Country review of irrigation, aquaculture, IIA activities and potential2

1 Togo and Sierra Leone were not part of the study.

2 NB - Discrepancies among figures may be attributed to the various sources and their methods of assessment.


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