9. CIFA/85/Symp. 10
FISHERIES IN SMALL WATER BODIES: AN OVERVIEW OF THEIR POTENTIAL FOR SUPPLYING ANIMAL PROTEIN TO RURAL POPULATIONS OF AFRICA

by

Garry M. Bernacsek
Fishery Scientist
Fishery Policy and Planning Division, FAO Rome

Paper presented at: Symposium on the planning and implementation of fisheries management and development programmes, 7–9 October 1985, Lusaka, Zambia. Held concurrently with the 6th session of the Committee for Inland Fisheries of Africa (CIFA).

… it is recommended that the role of fisheries in alleviating undernutrition be proposed as a specific action programme for fisheries development

- Norway/FAO (1983:12)

1. A STATEMENT OF INTENT

The intention of this paper is to attempt to open a discussion on small water bodies and their fisheries. It is directed primarily at the governments of the 56 countries and associated islands which constitute the geographical land area of Africa. It is the contention of the author that, by and large, the magnitude of the potential of small waters to supply dietary animal protein to the rural poor of Africa has never been adequately evaluated. The paper argues that small water body fisheries need to be recognized as a distinct sector of the inland fisheries panorama - distinct from large water bodies or artificial aquaculture ponds, possessing their own special characteristics and requiring their own particular development and management inputs.

Due to its brevity, this paper cannot be more than a discussion document. It focuses on general aspects of the environment and the fisheries. It can readily be appreciated, however, that such activities recommended herein as the construction of small dams and the planting of shade trees will have impacts far beyond fisheries production and so must be viewed as part and parcel of general rural development activities. Thus, it is also hoped that this paper may help to stimulate a discussion on the role of small water body fisheries in integrated rural development.

The author is very grateful to the following colleagues employed at FAO for their valuable comments and criticisms of the draft: A. Bonzon, J.J. Kambona, J.K. Kapetsky, G.W. Ssentongo, A.G.C. Tacon and M.M.J. Vincke.

2. PEOPLE AND SMALL WATERS

The total estimated population of Africa in 1985 is approximately 553 million¹ (United Nations, 1985). Some 28% are urban residents, many of whom live in large coastal capitals or ports (i.e., Lagos, Dakar, Algiers, Dar es-Salaam) or on the shores of a major inland water body such as Cairo on the Nile River, Kampala on Lake Victoria and Kinshasa and Brazzaville on the Zaire/Congo River. The remaining 398 million rural residents live in a variety of locations. While summary data is lacking, it may be safely assumed that a large percentage live in the vicinity of a small water body, be it natural lake, river, stream, floodplain, swamp, marsh, reservoir, agricultural dam, irrigation canal, coastal lagoon, mangrove swamp or estuary. Since large areas of Africa suffer from the triple “scourges” of highly seasonal rainfall, low runoff coefficient and periodic drought, the necessity of being located near some type of substantial surface water resource is obvious².

Such rural populations may depend heavily on their nearby small water bodies for a variety of needs, including drinking and cooking water, bathing, laundry and livestock and crop watering. It would also be common to find such a small water being exploited to some extent for fish (provided some resource is naturally present or has been stocked). Often this takes the form of gillnetting and basket trapping by adult men on a part-time basis and angling by children¹. Total catches are of course small by comparison to large water bodies and usually do not permit full-time professional occupations as fishermen. But the importance of a daily input of fish protein and nutrients into the diets of such populations (many of whose standards of living are well below the poverty level) should not be underestimated. In fact it does not appear to have ever been reliably estimated over a wide geographical area.

Small water bodies have often been ignored by fishery developers in Africa who have either focused on large inland waters and the seas or on aquaculture in artificial ponds. Small dams, for example, appear to be very underutilized in many parts of Africa (Bowmaker, 1975; Welcomme, 1977). Some exceptions fortunately exist such as past stocking programmes for small lakes and dams carried out in Tanzania (Bailey, 1966; J.J. Kambona, pers.com.), in Zambia (Republic of Zambia, 1972:36–7) and in Uganda (FAO, 1965:20). Often small lentic systems² are considered a health hazard because they may harbour disease vector organisms (snail and mosquito larvae) and so become the object of wet-land drainage and land reclamation. However, the development and enhancement of fisheries in small water bodies could be vital for the supply of animal protein to Africa's rural poor. It is estimated that by 1990 the urban population of Africa will have risen to 32% of the total - some 200 million people. This huge sector, largely unable to produce food to feed itself but with a disproportionately large amount of political power and financial means, will put increasingly heavy pressure on the inland and marine fish resources of the continent. It would not be unrealistic to predict that virtually all major commercial supplies of inland and marine fish will eventually be “appropriated” and redirected toward urban consumers with precious little of this harvest reaching poorer rural populations. Because of uneconomic transport and distribution costs small water body fish resources will probably always fall outside of this urban marketing network. In fact an important advantage of small water fisheries is the elimination of most marketing middlemen and transport costs, which keeps product prices low and affordable to the rural poor. In the long term therefore small water body fish, supplemented with poultry and small livestock, may represent the only secure prospect for self-sufficiency in animal protein and adequate nutritional health for much of Africa's rural population.

3. SIZES AND NUMBERS

The Appendix presents a brief summary of the small water body resources of 56 African countries and associated islands.

It is difficult to specify a definite upper size limit that defines small lentic systems qualitatively as well as quantitatively, and separates them from larger systems. For convenience Bernacsek (1984:6) classified African reservoirs as follows:

However, little is to be gained at present by too rigid a definition. One should keep in mind that productivity per unit area in lakes and reservoirs generally increases with decreasing surface area (especially so if the water body is both shallow and rich in chemical nutrients). Thus some smaller lentic water bodies support sizable commercial fisheries and in effect behave in a socio-economic sense more like larger systems than small systems.

It is also difficult to determine the total numbers and combined surface areas of small lentic systems in Africa. Table 1 presents an enumeration of lakes, impoundments and coastal lagoons, based on a recent search by Bernacsek (in preparation) of several thousand reports in the FAO Fisheries Library. The grand total of 19 437 is however likely to be a substantial underestimate since comprehensive inventories such as that for Mozambique (Romano, 1972) do not exist (or were not available for this study) for many countries. It is also impossible to give an accurate estimate of the total surface area for small lentic systems in Africa. Such information is only rarely available for individual countries (see Kiener (1973) for Madagascar and Ita et al. (1985) for Nigeria). Assuming that the mean size is somewhere between 1 and 5 km² it is obvious that the total surface area of small lentic systems is rather substantial.

Table 1

Enumeration of small lentic water bodies in Africa. Based on data in the Appendix

Small rivers are either single, integral drainage basins discharging into the sea or a large lentic water body, or are tributaries to large rivers. They may be defined (again for convenience) as lotic systems¹ ranging in stream-order from 1 to 6. Mean lengths are from 1.6 to 103.3 km (Table 2). Out of a theoretical total of 12.8 million km of river channels in Africa, some 12.7 million km (98.8%) consist of low-order (1 to 6) river streams. The 19 largest rivers (stream-orders 9 to 11) of Africa are by comparison a rather “rare” resource.

The numbers and size limits of other types of small water bodies such as inland and coastal floodplains, freshwater and mangrove swamps and marshes are presently simply not known nor readily definable.

Table 2

Estimated theoretical numbers and lengths of various orders of river channels in Africa. From Welcomme (1979:8, Table 2.1)

4. PRODUCING AND HARVESTING FISH IN SMALL SYSTEMS

Although morphologically different from each other, all types of small water bodies are subject to similar overall ecological and sociological influences which can differ radically from those of larger systems. Scale alone defines many of the “operational” characteristics. Catchment areas are usually small, but tend to deliver proportionately more runoff and sediment than larger catchments. This is because runoff volume per unit area increases with decreasing catchment area (see, for example, Karpiscak, Foster and Rawles, 1984). However, low-order streams are more subject to dessication during the dry season because there is relatively less infiltration of rain into the ground and thus less groundwater delivery outside of the rainy season. Small lentic systems may also suffer from excessive siltation which reduces their water storage capacity (= volume and depth) and eventually leads to swamp and marsh formation (and a coinciding loss in fish production - see Table 5).

Except for some crater lakes and some reservoirs lying over very steep riverbed gradients and impounded by rather high dams, most small lentic water bodies are shallow with mean depths of only a few meters at most. Annual evaporation in Africa can be as high as 2.8 m and so it is clear that most small lakes and reservoirs situated outside of humid rainforest zones will undergo partial dessication each year¹. If the annual rains are too light, many small lentic bodies may dry up completely during the following dry season despite the greater “efficiency” of small catchment areas in delivering runoff. In the event of an extended drought, all small systems over a large area will dessicate. Such an event presents not only the immediate problem of loss of fish protein to the diets of local people, but once the rains return and the water bodies refill, those without connections to larger systems which survived the drought will remain fishless until artificially restocked. Since evaporation is a function of both solar irradiation and wind, and is further increased by the presence of floating macrophytes, practices such as the planting of tall windbreaking shade trees along shorelines and the removal of floating vegetation can significantly reduce evaporation loss (as well as provide several other benefits such as supplying domestic firewood, improve soil quality from leaf litter accumulation, reduce disease vector organism habitat size and supply cattle fodder or garden compost).

Shallowness in lentic systems is the ideal condition for aquatic macrophyte growth. Thus, some small lakes are practically overgrown with macrophytes, either submerged or floating, or both, and dense stands of reeds or papyrus cover the shoreline. Lotic systems are also not exempt from plant infestation. For example, in Uganda many upland river valleys are completely covered with papyrus and it is estimated that some 30% of the Ugandan countryside may be papyrus swamp (Hickling, 1961:26; Beadle, 1974:246). A certain amount of submerged and marginal macrophyte growth would appear to be essential to good fish production. However, excessive growth quite definitely strongly depresses it. Indigenous African plant eating fish species such as Tilapia rendalli (= T. melanopleura) are adept at clearing submerged vegetation from lentic waters (Maar, Mortimer and Van der Lingen, 1966; Junor, 1969; Toots, 1975) but floating and shoreline vegetation usually requires manual or mechanical removal (Hickling, 1961:25–6) - up to 15 t/ha in the case of papyrus.

For both lentic systems small size results in higher shoreline length - to -surface area ratios (Tables 3 and 4). Furthermore, small rivers have extremely high ratios as compared to small lakes or reservoirs. For example, a small river 10 m wide will have a ratio of some 200 km of shoreline per km² of surface area while a small circular lake of 1 km² surface area will have only 3.5 km of shoreline. Although the point needs confirmation it would seem probable that agricultural population density or spacing along water body shorelines is somewhat independent of surface area of the water body. This implies that the number of persons settled per km of shoreline may be similar for large and small systems. A corollary to this is that small waters may tend to have a much larger number of shoreline residents per km² of surface area and therefore are subject to much heavier direct human impacts.

It is in the area of fisheries that this heavy population pressure will likely have its most profound effect since the volume of water available in even rather diminutive systems will usually substantially exceed that required for small-scale domestic and agricultural uses. Study of large lakes and reservoirs has shown that when fishing intensity exceeds 1 fisherman per km² such systems may be approaching full exploitation (Henderson and Welcomme, 1974). It can be readily appreciated that 2 or 3 extended family units settled on the shore of a small 1 km² lake could easily exert an effective fishing intensity in excess of the 1 fisherman per km² level, while the same 2 or 3 families similarly spaced along a small river could exert a fishing intensity bordering on the catastrophic. It is not clear that the 1 fisherman per km² maxim is applicable to small systems (or even that it is approximately correct for large systems). The present author is inclined to believe that the optimal fishing intensities are substantially higher. For example, the small 2.4 km² Lake Rutamba in southern Tanzania visited by the author in January 1980 supported some 115 part-time licensed fishermen (= 47.9 fishermen per km²) and had produced an estimated 79.4 t (= 331 kg/ha) in 1979 of mainly “stunted” tilapia which were nonetheless readily accepted by the local population. Regardless of the exact figure it would appear that heavy to excessive fishing intensity might be an almost inherent feature of small systems. This would place them in much greater danger of stock overexploitation and collapse than larger systems. More optimistically however, it also means that harvesting of available fish resources in small systems is much more thorough with far less “wastage” due to natural mortality¹. A greater percentage of the fish flesh produced in the system ends up on the dinner plate.

Table 3

Shoreline length-to-surface area ratios for various size lentic water bodies. The water bodies are assumed to be perfectly circular in shape^a

A Surface area	B Shoreline length		Ratio
1 km2	3.5	km	3.5	km/km2
10 km2	11.2	km	1.1	km/km2
100 km2	35.4	km	0.35	km/km2
1 000 km2	112	km	0.11	km/km2

^a Any deviation from a perfectly circular shape results in an increase in the shoreline/area ratio. Thus the elongate and irregular Cahora Bassa Reservoir (area = 2 665 km²; shoreline = 1 775 km) has a relatively high ratio of 0.67. In general natural lakes tend more towards circularity or ovality while reservoirs tend towards strong irregularity

Table 4

Shoreline length-to-surface area ratios for various size lotic systems. Channels are assumed to be perfectly straight and surface areas are calculated for 1.0 km long section

Channel length	A Shoreline length (both banks)	Channel width	B Surface area of channel section		Ratio
1.0 km	2.0 km	10 m	0.01	km2	200	km/km2
1.0 km	2.0 km	100 m	0.1	km2	20	km/km2
1.0 km	2.0 km	1 000 m	1.0	km2	2	km/km2

Table 5

Theoretical potential yields of small water bodies of various dimensions. Yields were predicted using the indicated regression equations
(from Bernacsek, in preparation)

*  Potential yield estimate is only for the stream-order channel indicated and excludes potential yields of its lower-order tributaries
C = total catch (t)
A = surface area (km²)
L = channel length (km)

Human inputs designed to increase fish production can theoretically be relatively more effective in small systems than in large systems, again mainly due to the scale effect. Manpower is available in relative plenty and small projects do not require expensive non-local materials or machinery since local resources usually suffice. Fish yield boosting projects such as manual removal of nuisance vegetation (i.e., papyrus or water hyacinth) for small lakes and swamps, or construction of check-dams across low-order streams to increase dry season pool size (Hickling, 1961:3–5, 24–6; Bowmaker, 1975) are communal, self-help and labour intensive activities that rural populations can carry out with only a minimum of expert supervision (if any is needed at all) and without incurring burdensome and unnecessary costs for “exotic” or imported materials and machinery. Such environment and fishery enhancement activities would probably be impossible to carry out on large water bodies solely on a labour intensive basis.

Supplemental feeding of fish is de rigueur as an aquaculture practice. However, no fisherman is likely to begin tossing cassava leaves or kitchen refuse into a large water body such as Lake Tanganyika - and for two very good reasons. First, it would be difficult to demonstrate to him that such a practice was having the desired effect, namely of increasing fish biomass in the lake above the natural production level. Second, there is no guarantee that, in the absence of some type of enclosure, any extra fish flesh produced by the supplementary feeding would not simply end up in the net of some other fisherman in the vicinity. However, as system size and absolute number of fishermen decreases and fishing intensity increases these counterarguments become less weighty and the beneficial effects of supplementary feeding can become very apparent. To the fisherman a small water body is more “personal” and less of a vast open resource belonging to everyone and to no one. Fishermen are much more likely to “stake out” fishing grounds and prevent the incursion of outside fishermen, who may have difficulty even getting access to the water body from the shoreline. Continuous feeding of fish with locally available plant and animal matter at specific points along the shoreline would likely lead to high catches around such sites, due to an “attraction” effect as well as increased biological production. The installation of pens or dykes in such a situation may even be unnecessary - an important consideration in countries where enclosures are prohibited by law. To give an example, supplementary feeding using rotten vegetation, old maize husks and the like is practiced by fishermen on the relatively confined waters of ahlos and whedos (manmade trenches, natural depressions in permanently marshy areas, natural drainage channels, old drainage ditches and manmade holes) on floodplains in southern Benin and excellent yields of 1 500 to 5 000 kg/ha are obtained (Di Palma, 1969:3). Tacon (1985) has outlined various aspects of developing a “village level” fish feeding strategy in Africa. Nutrient loading can further be increased by using animal dung (this will occur automatically if the drawdown zone of lentic systems is used for livestock grazing) and processed human sewage (Maar, Mortimer and Van der Lingen, 1966:98; Bowmaker, 1975:214).

The brush park (acadja) or refuge trap is another method for increasing fish production well above the natural baseline level that is suitable for widespread introduction into small lentic systems. Ultra high yields of up to 28 000 kg/ha can sometimes be realized (Welcomme, 1979:192–4; Welcomme and Kapetsky, 1981:3–4).

At this juncture it is impossible to give a reliable overall estimate of the potential production of Africa's small water bodies. It is however possible to generate a first approximation (order of magnitude) estimate. Regression equations were used to predict the potential yields for various categories of water bodies shown in Table 5. Combining these with the available data on water body numbers in Tables 1 and 2, some rough estimates of total potential can be derived. If it is assumed that the mean size of small lentic water bodies is somewhere between 1 and 5 km², it seems likely that the 1 000 small lakes might produce between 32 000 and 120 000 t. The 17 247 small impoundments could yield from 400 000 to 1 550 000 t while the 470 small lagoons from 4 700 to 24 000 t. The other 720 small lentic waters not classified by category might roughly produce anywhere from 16 000 to 62 000 t. Small rivers might produce total catches of 33 000, 69 000, 89 000, 104 000, 116 000 and 128 000 t for stream-orders 1 to 6, respectively. Summarized potential catch ranges are as follows:

By comparison the 1983 nominal inland catch (to a large extent based on recorded catches from large water bodies) was 1 420 000 t, while the nominal marine catch was 2 920 000 t (although at least as much again was caught by foreign fleets operating in African waters). Intensive pond-type aquaculture production is recorded as circa 30 800 t (Bernacsek, in preparation).

To the present rural African population of 398 million this potential yield from small water bodies would represent a per caput supply of between 2.5 and 5.8 kg/person. However, for several reasons the real potential supply may be rather higher:

1. a significant percentage of the rural population lives on the coast or near large inland water bodies and therefore would most likely not be consumers of small water catches;

2. an unknown (but thought to be substantial) number of small lakes, reservoirs and coastal lagoons were not enumerated in the present study, as well as the water body categories of swamps, marshes, floodplains, and mangrove swamps.

These considerations alone might increase the potential per caput supply by 50% to 100%, although future population growth would always tend to depress it again. Finally:

3. potential yield estimates are for “natural” fish production, and do not take into account such production enhancement techniques as stocking indigenous fish species to fill vacant ecological niches, supplementary feeding, eutrophication with human sewage, animal dung or agricultural fertilizers (either directly or from catchment area runoff) and installation of brush parks.

Such practices can raise catches rather significantly above the “natural” baseline level. As rural populations seek to produce more food such production enhancement techniques will undoubtedly become widely practiced. In the long term it is likely to be production enhancement rather than full exploitation which can enable rural populations to prevent population growth from depressing per caput supply.

A major problem, at least from the viewpoint of development planners, is that it is not clearly known what fraction of the potential small water body yield is already being harvested by rural populations. Nutrition surveys usually record fish as a distinct dietary item, but the source of the fish may not be exactly specified or the survey may cover only a small part of a country. To the author's knowledge the current total catch (= consumer supply) of small water body fish is not known for any African country. Pragmatically, it is however more important at this stage to carry out development activities designed to rapidly stimulate production, rather than to become too overly concerned with finding out what are the current catches since obtaining that information can be expensive and time consuming and will of course do nothing to increase production directly¹.

5. WHAT NEEDS TO BE DONE?

Many small water bodies are currently exploited to a varying degree by part-time fishermen. Production from these existing fisheries could likely be significantly increased in a fairly short space of time (2 to 4 years) if national and provincial government were to implement the following 3 point plan of action:

1. Inventorization of small water bodies. This is necessary for precise planning of extension inputs and can be done rapidly using existing large-scale topographical maps. Several important items of information can be obtained in this way (i.e., water body name and type; geographical location and connection to larger systems; surface area² of lentic waters; channel length and stream order of lotic waters).

2. Stocking with tilapia fingerlings. Government staff need to visit the water bodies, determine which species are present (if any) and then assist the fishermen in obtaining seed where necessary. Ideally the ichthyofauna should include a periphyton-eating tilapia species (such as Oreochromis niloticus) and a macrophyte-eating tilapia species (such as Tilapia rendalli). If indigenous species are lacking or unsuitable, non-indigenous species would have to be considered. Simple transport methods need to be devised so that rural fishermen can carry out their own stocking using seed from neighbouring water bodies and thus not become entirely dependent on government sources for seed. Existing government aquaculture facilities such as demonstration forms would have to be given over in part to producing seed, since in all cases local transfers by fishermen may not be convenient or sufficient. Such a programme was successfully carried out in Tanzania (see Bailey, 1966). Stocking rates as low as 500 – 1 000 fingerlings per km² were successful there.

3. Provision of inexpensive fishing gear. To harvest fish from small water bodies fishermen need appropriate fishing gear at prices they can afford to pay. It is necessary therefore to extend the national distribution network of inexpensive netting material to include rural retail shops and other outlets which are not situated near large water bodies but rather near small systems. Furthermore, to protect the fishermen from possible shortages in supplies of “outside” fishing gear and also because a segment of the rural population is too poor to buy ready manufactured fishing materials, it would be desirable to teach the use of local materials to construct fishing gear. This would include weaving netting from twine and constructing basket traps from reeds.

Implementing this three point immediate action plan would ensure that governments were aware of the magnitude and geographical distribution of their resource of small water bodies, that suitable stocks of food fish were present in them and that local populations had the technical capability to harvest this food crop.

A second programme of extension work of a more long term nature is also required with the specific aims of both preventing any decline in production from existing fisheries and increasing overall production by reclaiming and enhancing deteriorated environments, creating new water bodies by dams, enhancing production by various aquaculture practices and stocking selected species or genetic strains. Specifically, long term programmes should include some or all of the following elements:

1. Monitoring of both the fish production and the environment to determine when particular extension inputs may become necessary or desirable. In this regard, remote sensing by satellite may be particularily useful for continuously monitoring small water body surface areas for an entire country or group of countries and can be an integral part of a general national agricultural/vegetation monitoring system.

2. Construction of small-dams across low-order streams to increase dry season pool size and across discharge outlets of lakes and swamps to increase water level/volume.

3. Planting of shade trees along shorelines to reduce evaporation water loss and provide firewood.

4. Clearing of nuisance aquatic vegetation to reclaim open water habitat and increase oxygen levels in overgrown water bodies.

5. Bush clearing¹ in new or existing reservoirs to increase catchability of fish stocks, remove anchorage points for floating vegetation mats and eliminate navigational hazards (see Maar, Mortimer and Van der Lingen, 1966:81–7). Bush clearing may be total in the smallest reservoirs and selective in more extensive reservoirs.

6. Introduction of supplementary feeding, fertilization with organic wastes and brush parks to increase ichtyoproductivity above the “natural” baseline level.

7. Stocking of selected indigenous (or exotic, if warranted) fish species to fill vacant ecological niches. This can include pelagic planktivores (such as clupeids, some small cyprinids, some small characids), piscivores (such as the hardy Clarias spp.), insectivores (such as small mormyrids and schilbeid catfishes), salt tolerant species (such as soles and mullet) and species for control of disease vector organisms (such as Astatoreochromis and some Synodontis for controlling snails and Gambusia, Aplocheilichthys, Nothobranchius, other cyprinodontoids for controlling mosquito larvae - see Maar, Mortimer and Van der Lingen, 1966:99–103, 143–4). Coupled with this might be the introduction of improved genetic varieties of selected tilapia species with higher productivity and/or less sensitivity to environmental stress and parasites¹.

8. Compilation, collation and analysis of the existing widely scattered body of scientific and technical literature on small African water bodies. A particularly urgent need is the writing of guideline manuals for the use of extension workers.

9. Initiation of a multidisciplinary, problem-solving research programme aimed at full utilization and conservation of small water bodies. The programme must have direct linkages with rural extension workers for rapid transfer of new methods and techniques to the rural populations and to receive feedback on implementation success or failure. A major objective of the programme would be the adaptation and transfer of appropriate components of the large gamut of existing traditional and modern aquaculture practices to small water body fishermen. Of particular urgency is the formulation of emergency tactics to be used to combat the effects of drought on both the environment and the fish stocks.

In a practical sense small water body fisheries are a “third way forward” in Africa, complementary to large inland fisheries and to marine fisheries. They represent an opportunity to successfully implement aquaculture practices in a manner appropriate to the African situation and integrated with the African concept of fish production² - something which has often eluded aquaculture developers seeking to duplicate Asiatic or Western approaches in Africa. However, it must be stressed that the impact of these proposed immediate and long term programmes of action will depend on how successful fishery managers and developers are in convincing their governments (as well as outside support agencies where necessary) of the importance of small water bodies in providing dietary animal protein to the rural poor. Strong political will and motivation will be necessary to push through these development activities - which lack the glamour of large-scale projects and stand to benefit neither urban populations nor the better off rural elite - but which may be crucial for the eradication of malnutrition from the poverty-stricken rural sector of the African continent.

6. REFERENCES

Bailey, R.G., 1966 The dam fisheries of Tanzania. E.Afr.Agric.For.J., 32(1):1–15

Beadle, L.C., 1974 The inland waters of tropical Africa. London, Longman, 365 p.

Bernacsek, G.M., 1984 Guidelines for dam design and operation to optimize fish production in impounded river basins (based on a review of the ecological effects of large dams in Africa). CIFA Tech.Pap., (11):98 p.

Bernacsek, G.M., Sourcebook for inland fishery resources of Africa. Rome, FAO (in preparation)

Bowmaker, A.P., 1975 Protein production from fresh water, with particular reference to Rhodesia. Rhod.Sci.News, 9(7):212–6

Di Palma, S., 1969 The fisheries of Dahomey, 1968. Foreign Fish.Leaf1.U.S.Fish Wild1. Serv., (175):8 p.

FAO, 1965 Experimental fish culture project in Uganda. Report to the Government of Uganda on the experimental fish culture project in Uganda 1962–64, Based on the work of Yoel Pruginin, FAO/EPTA fish culturist. Rep.FAO/EPTA, (1960):

Henderson, H.F. and R.L. Welcomme, 1974 The relationship of yield to morpho-edaphic index and numbers of fishermen in African inland waters. CIFA Occas. Pap., (1):19 p. Issued also in French

Hickling, C.F., 1961 Tropical inland fisheries. New York, Wiley and Sons, Inc., 287 p.

Ita, E.O., et al., 1985 Inventory survey of Nigeria inland waters and their fishery resources. 1. A preliminary checklist of inland water bodies in Nigeria with special reference to ponds, lakes, reservoirs and major rivers. Based on surveys conducted by the Fisheries Division of Kainji Lake Research Institute. Tech.Rep.Ser.Kainji Lake Res.Inst., (14):51 p.

Junor, F.J.R., 1969 Tilapia melanopleura Dum, in artificial lakes and dams in Rhodesia with special reference to its undesirable effects. Rhod.J.Agric.Res., 7:61–9

Karpiscak, M.M., K.E. Foster and R.L. Rawles, 1984 Water harvesting and evaporation suppression. Arid Lands Newsl., (21):11–7

Kenmuir, D.H.S., 1981 Fish production and farm dams. Zimbabwe Agric.J., 78(6): 209–14

Kiener, A., 1963 Poissons, pêche et pisciculture à Madagascar. Nogent-sur-Marne, Centre Technique Forestier Tropical, 160 p.

Maar, A., M.A.E. Mortimer and I. Van der Lingen, 1966 Fish culture in central East Africa. FAO Fish.Ser., (20):158 p.

Norway/FAO, 1983 The potential of fisheries in alleviating undernutrition. Report of the discussions and conclusions of an Expert Consultation on the role of fish and fisheries in world nutrition, held at Gaustadblikk Mountain Hotel, Norway, 3–10 July 1983. (The Consultation was organized by the Government of Norway with the cooperation of FAO). FAO Fish.Circ., (761):13 p.

Republic of Zambia, 1972 Annual report for the year 1970. Annu.Rep.Minist.Lands Nat. Resour.Dep.Wildl.Fish.Nat.Parks, Lusaka, (1970):45 p.

Romano, M.P., 1972 Recursos permanentes de agua, em Moçambique (Ríos de caudal permanente e lagos con agua durante todo o año). Divulg.Serv.Agric.Serv.Vet. Moçambique.(Publ.Ser.B), (35):75 p.

Tacon, A.G.C., 1985 Fish feed technology. Paper presented at Commonwealth Consultative Workshop on village level aquaculture development in Africa. Freetown, Sierra Leone, 14–20 February 1985, 7 p. (mimeo)

Toots, H., 1975 Control of aquatic vegetation in farm dams. Rhod.Agric.J., 73(4): 87–91

United Nations, 1985 World population prospects. Estimates and projections as assessed in 1982. New York, United Nations

Welcomme, R.L., 1977 Inland fisheries in arid zones. In Arid land irrigation in developing countries: environmental problems and effects. Based on the International symposium 16–21 February 1976, Alexandria, Egypt, edited by E.B. Worthington. Oxford, Pergamon Press, pp. 303–6

Welcomme, R.L., 1979 Fisheries ecology of floodplain rivers. London, Longman, 317 p.

Welcomme, R.L. and J.K. Kapetsky, 1981 Acadjas: the brush park fisheries of Benin, West Africa. ICLARM Newsl., 4(4):3–4

APPENDIX

Summary of occurrence of small water bodies in 56 African countries and associated islands

Emphasis is on the more important water body categories in each particular country. Data was abstracted from Bernacsek (in preparation)

¹ Medium variant estimate

² Many smaller urban centers are also located near a small water body for similar reasons

¹ Angling may be a particularly effective and appropriate method for harvesting fish from small systems (see Kenmuir, 1981)

² Lentic systems may be defined as expansive water bodies with low or zero flow rates (i.e., lakes, reservoirs, swamps, coastal lagoons)

¹ Lotic systems are elongate flowing water courses such as rivers, streams and brooks

¹ Coastal lagoons are somewhat exempt as they have connections (either surface or subsurface) to the sea and also benefit from the more constant flow of runoff in higher-order streams, some of which may discharge directly into a lagoon before reaching the sea

¹ Also less of the available nutrients are “wasted” on older adult fish who have a poor food conversion ratio and thus produce fish flesh less efficiently than smaller individuals.

¹ In any case, for such “diffuse” fisheries well designed nutrition surveys might be able to generate this information more readily than catch surveys

² Can be roughly estimated as: length × width × 0.7

¹ The installation of brush parks and the removal of bush from reservoirs require comment since at first glance these two activities might be construed to be mutually self-defeating. Brush parks constitute a highly sophisticated fishing system. They are structures of specific design, construction and operation and are under the full control of the fisherman. They greatly increase fish production above the natural level and this increase is directly harvestable by the fisherman. Natural brush left standing in reservoirs usually provides a larger crop of periphyton and aquatic insects for fish to eat and thus results in a higher fish production than would occur if the bush were cleared prior to dam closure. However, submerged natural bush also reduces the catchability of the fish by interfering with nets, with the result that the actual yield to the fisherman may be less than if the reservoir had been cleared of bush. While both brush parks and submerged natural bush increase biological productivity relative to a structureless lentic system, only brush parks are known to significantly and reliably increase fish catch.

In passing it may be noted that bush park construction requires a large quantity of wood. This can be obtained initially from reservoir bush clearing and subsequently from shade tree plantations along the shoreline (see section c above)

¹ Introduction of improved genetic varieties is a standard procedure in crop and livestock agriculture. If, after rigorous evaluation, no foreseeable danger of environmental calamity is apparent, it would be short-sighted and unjustifiable not to carry out similar practices in the field of small water body fisheries if a worthwhile benefit can reasonably be predicted. While some water bodies possess unique endemic fish faunas worthy of complete protection from adverse competition with introduced species, the vast majority of African water bodies do not fall into this category

² The African concept of fish production may in general be defined as the extraction of naturally occurring fish from a nearby water body. Management intensive practices such as acadjas or pond aquaculture are the exception rather than the rule