WORKING DOCUMENTS (continued)

THE FISHERIES ECOLOGY OF AFRICAN FLOODPLAINS (continued)

8. EFFECTS ON FISHERIES OF OTHER USES OF THE FLOODPLAIN

Like many other freshwater systems, floodplains fulfil a range of functions other than that of supporting fish and fisheries. Most of these are associated with the dry phase (see Section 4) and do not greatly interfere with the fisheries productivity of the flood phase; certain activities may even be beneficial as in the case of dung dropped by grazing animals. Thus, a floodplain such as that of the Ouémé delta, which is one of the most intensively managed in Africa using traditional methods, successfully support herds of cattle and vegetable and cash crop farming alongside an intensive dry season floodplain pool fishery and an extensive flood phase fishery.

Major conflicts with fisheries occur in management schemes involving either the alteration of the hydrological cycle or the contamination of the environment.

8.1 Dams

Dams installed upstream of the floodplain: To date, dams installed upstream of the floodplain system are the main disruptive agency. The Lower Volta floodplain has disappeared completely following the construction of the Akosombo dam (Hall and Pople, 1968). Considerable areas of the Niger River floodplain have been lost below the Kainji dam where the flood regime has been altered as far downstream as the Benue confluence and fish catches have diminished to between 47 and 75 percent of their original values (FAO, 1972). The closure of the J.F. Strijdom Dam resulted in the complete dessication of many of the floodplain pools of the Pongola River (Phelines, Coke and Nicol, 1973) although here controlled release of flood water refilled the pools and induced breeding in the fish in 1969 and plans are going forward for the fishery to be maintained by this means.

Dams installed upstream of the plain may not necessarily disturb the hydrological regime but may interfere with the normal migratory pattern of the fish preventing their dispersal fully throughout the river as on the Niger (Daget, 1960a).

The effects of two projected upstream dams have also been assessed for Senegal and Zambia. In Senegal, the closure of dams in the upper course of the river would result in the loss of some 7 000 tons of floodplain fish production although nearly twice this might be gained from the dams themselves. The creation of the Itezhi-Tezhi Dam on the Kafue might have a beneficial effect on fish stocks by the regulation of water levels to create improve floods and longer retention time of the kafue Gorge dam downstream (Muncy, 1973).

Dams installed downstream of the floodplain: These generally result in a loss of the flood plain by its complete submergence. The transformation of the area to permanent lake will generally produce similar or increased fish yields at the sacrifice of alternative dry season forms of production. Dams which are designed to retain water in the floodplain for a longer period will theoretically improve yields by prolonging the flood phase (University of Idaho, 1971; University of Michigan, 1971) although there is, at present, no evidence of this happening in the case of the Kafue Gorge dam (Muncy, 1973).

8.2 Irrigation

Little is known of the effects of irrigation projects on the fisheries component of floodplains, although it is to be anticipated that the shortening of the flood cycle, due to improved drainage, would affect the population of fish adversely. There is, furthermore evidence that channelization of streams considerably reduces both ichthyomass and species diversity (Congdon, 1973). On the positive side, a larger dry season area of water in irrigation canals and reservoirs could improve survival and low water fish yields. In fact many of the Ouémé floodplain whedos were originally drainage canals.

8.3 Pollution

Pollution is at present not a serious problem in Africa although the use of fertilizers and insecticides, associated with intensive agriculture, could conceivably be a source of trouble in future.

9. CONCLUSIONS

9.1 Models of Floodplain Fisheries

The diagramatic models presented here are simple summaries of the foregoing material. They are neither detailed nor complete and are intended to serve as a basis for the formulation of certain principles for the management of floodplains and also to indicate the direction of future research by identifying gaps in our present knowledge.

The changes occurring over one complete floodplain cycle are summarized in Fig. 11. These changes can be represented in cyclic form showing the nutrient/energy flow within the system (Fig. 12). It is known that the rate of alluvial deposition equals the removal of alluvial matter by erosion over a period of years (Leopold, Wolman and Miller, 1964). It may be assumed that, in the wild state, a similar dynamic equilibrium occurs with respect to the nutrient and biomass. If such an equilibrium does exist, then the productivity of one component may be affected by the bad management or overexploitation of one of the other components, or by some other intervention affecting the input of salts, for example. In this respect, Kapetsky (1974) examines the evidence for a diminution in fish population in the Kafue Flats resulting from the reduction of the primary users of floodplain vegetation, i.e., Lechwe and Hippopotami.

Figure 11. Summary of the major cycles of a floodplain throughout the year

Figure 12 Diagram of nutrient and energy cycles on the floodplain

The inter-relationships of factors affecting the aquatic phase of the cycle only are presented by the University of Michigan (1971) (Fig. 13). This figure is especially valuable in indicating future lines of research as many of the interactions shown will be quantifiable for various floodplains. Elucidation of these should lead eventually to better management practices and maximization of yield.

A synthesis of the factors described in Sections 5, 6 and 7 can be used to construct hypothetical curves for growth, number and ichthyomass throughout the year (Fig. 14). This shows the number of fish to increase rapidly as a result of reproduction (R) during the earlier part of the flood and then decline due to natural and fishing mortality during the period of falling water (Z', F') and at low water (Z", F"). A period of especially high mortality (Z"') might occur during the latter part of the drawdown period when large numbers of fish are trapped and die in impermanent pools by the retreating waters. Rapid growth (g') occurs during the earlier part of the flood but declines in rate (g") during low water. The resulting curve for ichthyomass increases rapidly during the floods, declines sharply during the drawdown period and continues a slow decline during low water until the onset of the next floods.

Year-to-year variations in the curve result from changes in hydrological regime; good floods producing high values of R and G' and lowered values of Z' and F'. The retention of a large amount of water in the system throughout the dry season will produce similarly heightened values of G" and depressed values of Z" and F" giving an improved value I at the end of the cycle. Poor floods and a lessened water retention would produce the opposite effect.

In addition to the absolute values of flood height and water retention, the abruptness of change may also influence certain factors. Thus, a slow rise in level at the beginning of the floods is thought to be more favourable to reproductive success (R) than an abrupt rise. Similarly, rapid drawdown, which does not give fish adequate time to leave the plain, would result in increased values of Z"'.

9.2 Management of Floodplains

General: Floodplains should be managed for the full realization of the potential for both dry and wet season crops of which fisheries are but one component. Thus, elements A, B, C and D from Fig. 14 should be so adjusted as to maximize their sum. In some cases, maximization of an individual component may only be pursued to the detriment of another. Thus, for maximum production of rice, the use of insecticides against stem borers and herbicides to clear irrigation channels may be necessary and a drop in fish production could result. Similarly, maximization of dry season agriculture could require rapid drainage of the floodplain to increase the length of the dry phase which could result in a diminution of the fish population.

The best managed floodplain observed to date is that of the Ouémé valley where, during the dry season, artificial fish ponds alternate with maize fields (Fig. 8) and vegetables are grown on the raised banks of the ponds. Cattle are grazed on the raised levées which also support stilt villages with an aggregate population of 70 000 inhabitants. During the flood season, activities have hitherto been confined to fishing although recently limited floating rice culture has been introduced. The cultivation of rice under these conditions does not appear to conflict with the presence of fish although some species are known to attack the plants to a limited degree.

The improvement of dry season yields by digging of fish ponds, or by the improved retention of water in pools by dams, seems to be the most logical step for many floodplains although many trials are necessary before the best methods can be defined.

Figure 13 Some interrelationships of factors affecting fish production on floodplains
(form University of Michigan, 1971)

Figure 14 Diagramatic representation of changes in:
A Water level
B Number (dotted line), Growth of year class 1 (dashed line) and Ichthyomass (solid line) during one annual cycle of a theoretical floodplain fish population.

Management of the fishery: The wild fishery usually concentrates on three points of the annual cycle and any policy for the rational management of stocks of fish should aim at defining and controlling these. At present, there is little definite information on this and needs are likely to vary from area to area but some general guidelines can be laid down based on existing fisheries.

1. Migration at beginning of flood: Fisheries exploiting migrating fish before reproduction generally seem to be harmful to the fish stock. Additional pressure is laid on the population at its weakest period and numbers of breeding fish can be seriously reduced. At least two important fisheries, that for Labeo victorianus in the Nzoia River (Cadnalladr, 1965) and that for Labeo altivelis in the Luapula (Soulsby, 1959) have collapsed due to overexploitation at this time. It therefore seems advisable to discourage this practise under normal circumstances.

2. Return migration of juvenile fish: Fisheries aimed at the capture of migrating fish as they leave the floodplain are widespread and much difference of opinion has arisen on the harmfulness of this practise. It has been widely supposed that most of the juveniles returning to the river are destined to die due to the restricted environment available to them in the dry season. This may well be true in the Niger River or the Barotse floodplain where neither Reed (FAO, 1969) nor Bell-Cross (1971) considered that the practise was particularly harmful.

Management of the hydrological regime: In areas where the channel upstream of the floodplain is blocked by a dam, controlled release of water may simulate normal flood conditions and ensure the maintenance of the fish stock. This is probably easier in systems with large permanent lakes and pools, as these are readily refilled and fish induced to migrate into them to breed (Phelines, Coke and Nicol, 1973) than in systems with large dried floodplains as here the production depends on the duration and intensity of the flood. Nevertheless, in most floodplain areas a better understanding of the ecology and biology of the fish should enable programmes for floodwater release, suitable for the maintenance of at least a limited fish stock, to be worked out.

Acknowledgements

The author wishes to thank all those fishery workers who, by replying to the “CIFA information form for summary of data on floodplains”, expanded the scope of this document to include many lesser known areas.

Thanks are also due to the many colleagues of the Fishery Department of FAO with whom these problems have been discussed.

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EVOLUTION OF THE FISHERIES IN THE LAKE CHAD BASIN AREA DURING THE LAST FIVE YEARS

by

A. Stauch
and
O.K. Oji-Alala

1. INTRODUCTION

Lake Chad as well as the lower Chari River, which is the tributary that carries roughly 95 percent of the water contribution coming from rivers, represent for the four bordering countries a very important resource of proteins. More than four fifths of the fish produced in this area is marketed and consumed in Nigeria.

But because of the irregular rainfalls in this tropical area (the latitude of the basin is under an arid and a subarid climate), the surface area of Lake Chad is subject to great variation. In addition, the permanence of winds and the presence of dry air masses during a part of the year are some of the factors which encourage water evaporation.

About 10 000 years ago, Lake Chad was an inland sea of the same surface area as the Caspian Sea today. In 1961–62, the surface area of Lake Chad was roughly 24 000 km². In 1973, the same lake was divided into two small water basins separated by the “grande barrière” and representing roughly 7 000 km². There is no doubt that the lake follows a natural cycle, but owing to inadequate data, we cannot ascertain this cycle.

2. THE FISHERIES

Before 1945, Lake Chad was not exploited very much. The occupation of the riverine population was especially cattle rearing and little farming activities around the settlement. Another factor which also broke down the economic development was the war existing among the different sultanates or emirates. For some tribes in the area, fishing was a degrading activity and only slaves or “Haddad” could do it.

With the modernization of the road infrastructure and transport facilities, fisheries changed from a subsistence activity to a big industry, with exports to a larger area and to countries lacking protein food.

However, since 1964 we have been living in a dry period. Flood contributions of River Chari have been deficient and a progressive reduction of water surface has been observed With reducing water area the catch steadily increased after this period.

3. FISH STATISTICS

3.1 Considering the orographic nature of the basin, fishermen can settle anywhere they like, and also fish traders can reach the temporary fishing centres either by lorries, or by the traditional camels, donkeys, etc.

In this period, to collect landing statistics was quite impossible without a strong and logistical support. First because the fishermen never stay a long time at the same place. They carry their equipment from one place to another by boat, moving among the islands, the archipelago and the shore. Therefore, it has been very difficult to follow their movements and study their catch. On the other hand, it has to be noted that Lake Chad is an international body, divided into four parts, and for the fishermen, the political boundaries do not exist. They move according to the seasons, the fluctuations of the water levels and the breeding grounds.

3.2 At several places on the shore, trials were made to set up landing statistics teams. The work was carried out by Government fishermen remunerated by the Ministry and, of course, their work and catch could not be compared with ordinary fishing because their working time and methods were too different. For this reason, landing statistics on Lake Chad is a problem which is still unsolved.

4. TRAFFIC CENSUS

In general, the lorries carry traders, fishermen, gear, petrol for outboard engines, etc. to the lake shore. On the shore the traders who hire the lorries go on appointments with wholesale traders who come by boat from the fishing camp. Sometimes several traders hire a lorry together; at other times a lorry may belong to a single owner.

From the shores, the trucks have to go through Maiduguri before going to the south. For this reason, we set up in this town, at the entrance of the roads from N'Djamena (former Fort-Lamy) and from Baga, two checkpoints for the purposes of gathering information from all the lorries or other transport means carrying fish and collecting data on the number of packages, the nature of the fish, yield, etc. The work started on 1 July 1969 and has since been continued daily up to now.

5. ANALYSIS OF THE DATA OBTAINED DURING FIVE YEARS (1.7.69 – 30.6.74)

5.1 N'Djamena Road

5.1.1 As shown in Annex II fish is carried in the trucks from Wulgo and Gambaru. But these two towns are located near the boundary with Cameroon and roughly all the fish landed in these places is caught either in Cameroon or Chad.

Wulgo is located on the lake shore at the mouth of the El 'Beid River and Gambaru on the road linking Maiduguri to N'Djamena. Under normal conditions, Wulgo is a terminus. Crafts which are either mechanized, or propelled by paddles or poles, come from Cameroon or Chad and unload the fish bags after having passed through the channels and drains bordering the lake shore. In general, fishermen do not carry the processed fish but middlemen linking the temporary camp to the landing places. In the last two years, however, because of the dramatic drought, Wulgo area was completely dry and far from the open waters, a distance of over 30 km. Consequently, the traders had to abandon their former transporting routes to adopt other transporting methods. Lorries from Cameroon have to load the catch on the river banks or the lake shore, and later on to unload at the boundary. From the boundary, labourers, either by head load or hand pushed trucks, carry the fish across the boundary from Cameroon to the Nigerian side and the fish is then carried by lorries to Maiduguri and the south. It has to be specified that the calculated production at this checkpoint is not only from the lake, but also from the delta and lower Chari River tributaries like Serbewel, Taf-taf, the lower Lagone River and the Yaere. It is not possible to differentiate the origins of production.

5.1.2 As can be seen in Annex III the fish coming from Chad and Cameroon represents a very small quantity of the grand total. It should be noted also that the salanga catch in Cameroon only gets to Maiduguri while in transit and goes back again to Northern Cameroon through Bama-Mubi road. This circular tour is partly due to the unauthorized movement of lorries through Waza road. It is interesting to note that the salanga production, which decreased in 1971–73, increased again in the last 12 months because of the improvement of the salanga fisheries in the lake itself.

Mention must be made regarding Annex V that the production progress index for the southern part of the lake is much lower than the northern one.

5.2 Baga Road

5.2.1 The whole fish coming through this check point is produced in the lake except for a very small tonnage of salanga harvested in the Komadugu River during its short flood period.

5.2.2 The yearly increase of production comes from Malamfatori, a town located on the lake shore less than 8 km south of the Niger boundary. Effectively, as a result of the drought and hence the recession of the lake, Malamfatori has become the best point to centralize production, especially banda. The fishermen settle in the islands which form a sort of fringe bordering the northern and eastern part of the northern basin now separated from the southern basin by the “grande barrière”. The increase of the salanga catch at Baga is due to the improvement of the Alestes fisheries in the lake in the last twelve months.

5.3 In Annex I we give the evolution of the production during the last five years.

5.3.1 It is shown that the northern part of the lake, even before its separation from the southern basin was more exploited, as shown in Annex X. However, before the end of the fifties, the southern part was better exploited than the northern part because transport facilities at this time were better in the south. The Maiduguri-N'Djamena road was the easiest link for carrying processed fish to southern Nigeria. Comparatively, the demand for fish at that time was not as high as now. The factors that forced the fishermen to extend their activities were as follows:

• the construction of Maiduguri-Baga road

• the modernization and improvement of transport facilities

• increase of human population and higher demand for fish in southern Nigeria

• arrival of fishermen from the Niger-Benue basin

• the increase of the prices at both ends of the link

5.3.2 Nevertheless, the reduction of the surface area of the lake due to the drought, led to a concentration of the fish population and hence favoured easier and higher catch.

But on the other hand, it must be stressed that some of the part-time fishermen abandoned their fishing activities because the fishing grounds became too far and inaccessible. Their equipment was no longer adequate for effective fishing. The better equipped full-time fishermen could settle near the new fishing grounds and thus increase their revenue.

Note:- Banda: is prepared from fish cut out, scaled, eviscerated and then sun-dried for a few hours on papyrus mats which are then scorched for a few minutes. The pieces of fish so scorched are allowed to dry in the sun for 3–6 days. They are finally packaged.

Salanga: this product is made from Alestes dentex and Alestes baremoze and prepared by allowing the fish to sun-dry for a few days after it has been eviscerated and split open.

6. ESTIMATION OF THE PROCESSED FISH

6.1 In Annex IV we can follow the fluctuation of the destination points where the fish is distributed to the retailers or consumers, especially in the former war-affected areas.

It could however be observed that some big towns, Ibadan, for example, even increased their fish consumption, but this was influenced by their economic development.

6.2 N'Djamena Road (Fort-Lamy)

Roughly 70 percent of the banda is purchased in the southern part of Nigeria.

Concerning salanga, it has to be mentioned that the hill areas near Mubi and Bama represent for Nigeria the most important consumers. In the last twelve months, 70 percent of this fish passing through Gambaru checkpoint was sent back to Cameroon for reasons earlier stated.

6.3 Baga Road

Approximately, the same observation can be made as above. A part of the salanga is unloaded at Maiduguri for repacking at the fish market before later distribution to other areas. Anyway, it should be pointed out that salanga is especially needed in the hill areas. In some places, tradition prohibits the consumption of smoked fish.

Concerning banda, Lagos is the highest consumer of this type of processed fish. But it seems that from Lagos a small part of this product is sent somewhere else and we know that some lorries carry banda to Ghana. There is a high demand for salanga in Lagos and we wonder why more of this fish is not sent to the south. Of course, the packaging method is different from that of banda and it seems that transportation method does not presently favour salanga.

7. FLUCTUATION OF THE PRICES¹

7.1 The prices of fish have been continuously changing over the years depending mostly on the rate of production of fish, sometimes on the availability of transport and road facilities and on the season. We observe however that contrary to general expectation, the higher rate of production did not necessarily correspond to increase in price.

Fish prices depend on the grade of the fish and packaging method. But taking a jute sack as standard for banda, and mats for salanga, the fluctuations are as follows:

7.2 Banda

7.2.1 Islands (North and Northeastern part of the lake). In general, one sack of banda costs N.15.00 (5 000 CFA); but on the shore the price range is N.30-N.40 (10 000–13 000 CFA).

7.2.2 Shore on shore the prices are influenced by the cost of carrying and unloading the fish. The cost of carrying the sacks of fish from the Islands to the shore, depending on the distance, is about N.3–N.4.00. If the fish passes through customs posts of any of the countries, especially Niger and Chad, the price increases by over N.6.00 (2 000 CFA).

7.2.3 Consumer Areas: As mentioned earlier, most of the production is consumed in the southern part of Nigeria.

Mann (1960) reported that at Maiduguri, banda was sold at an average price of 35 k/kg, equivalent to about N.14.00 per sack of average weight of 40 kg. Price per sack of same average weight in August 1974 in Maiduguri was about N.30.00 and in the south, the price of a sack is about N.45.00. In 1968, Couty mentioned that the price of 1 kg of banda in Chad was 80–90 CFA (3 200–3 600 CFA/sack).

7.3 Salanga

Prices obtained were as follows:

7.3.1 Islands (North and Northeastern part of the lake). Generally, salanga is packed in mats of 1 000 sun-dried fish of an average weight of 70 kg. Each mat costs about N.15.00-N.20.00 (4 000–7 000 CFA).

Shore As in the case of banda, about the same amounts of money are paid for handling.

7.3.2 Consumer Areas: Couty (1968) mentioned that 1 kg of salanga was valued at 45 CFA (3 150 CFA/mat) in Chad.

In August 1974, at Maiduguri market, the retail price was 80 k for 12 salangas, equivalent to N.67.00 per mat. Data on the distribution of salanga are few but this could form a basis for a future socio-economic survey.

7.4 Discussion

With the available figures, it seems that the prices between 1960 and 1968 did not fluctuate significantly but thereafter there has been a steady rise in prices, possibly due to general economic development of the country. It is evident from information available that from 1960 to 1974 there has been about 100 percent increase in the purchase and selling prices in the producer area. However, as the figures show, there has been an increase of 75 percent in the consumer areas within the same period. It does appear therefore that as the prices in the production area rose strongly because of high demand, the prices in the south, which normally should follow the same trend, did not rise, due probably to the availability of fish in the consumer market from marine, brackish water fisheries or fish farming.

The estimated total production of the Lake Chad basin area in 1973/74 gives about 45 000 tons of processed fish which represents more than N.30 million. Twelve thousand tons of processed fish checked in 1969/70 represented N.4 million. In Annex XI, the production trend in the last five years calculated at both checkpoints could be followed to give an insight of the catch. The data show that within the five years of observation, the catch increased by approximately four times and the value within the same period increased by nine times.

¹ U.S.$ 1.00 = CFA 240
U.S.$ 1.64 = N.1 (Naira)

8. CONCLUSION

It could be reasonably extrapolated that the catch increase of the last five years has been a result of the strong reduction of the surface and the water volume of the lake. From available data transmitted by ORSTOM (N'Djamena), we could speculate that the water in the lake will soon increase and the tendency would be that the fish population would spread in a wider area and the catch automatically decrease. This is bound to affect directly the fisheries industry in the basin. Some full-time fishermen are likely to move to other fishing areas on experiencing lower income. On the other hand, some part-time fishermen, who formerly abandoned fishing activities because of the increasing distance between their settlements and fishing grounds, will again resume fishing. In this eventuality the authorities concerned should forewarn the fishermen of the possibility of lower catches. This certainly will be a short and temporary period which will be followed by a new equilibrium in the fishing activity of the lake after some two or three years, depending on the fish species.

9. REFERENCES

Couty, P., 1968 Le poisson salé-séché du Lac Tchad et du Bas-Chari: Prix et débouchés. Dakar: ORSTOM

Mann, M.J., 1962 Fish production and marketing from the Nigerian shores of Lake Chad 1960–61. Lagos, 48–9

Annex I
BAGA ROAD (IN METRIC TONS)