COUNTRY FILES (contd.)

NIGERIA

1. GEOGRAPHY AND CLIMATE (Welcomme, 1979)

Nigeria (with a surface area of 910 770 km²) has four main topographic areas. There is a hot, humid coastal belt which varies in width between 16 and 90 km and is covered with mangrove forests. Inland from this, there is a tropical rain forest zone which penetrates up to 160 km into the interior. The central plateau of the country is high (2 000–2 500 m), relatively dry and covered with open woodland and savanna. The extreme north of the country is semi-desertic and lies within the Sahelian zone.

There are two well-marked seasons during the year. The wet season, and a dry season which lasts from October to April in the north and from November to April in the south. The climate becomes progressively more arid toward the north of the country.

Although Nigeria is predominantly agricultural, there is an active petrochemical industry in the Niger Delta area and industrial development is expanding, particularly in the south. Heavy urbanization along coastal rivers and lagoons, and intensive agriculture for cash crops in some other parts of the country, may give rise to local pollution problems.

2. HYDROGRAPHY (Fig. 1; Tables 1, 2)

2.1 Lakes

During the “Normal Chad” phase, 5 500 km² (25%) of Lake Chad lie within Nigeria. However, during the “Little Chad” phase, the waters of the lake are concentrated entirely within Cameroon and Chad, and the Nigerian portion virtually disappears.

There are numerous (about 100) small lakes scattered throughout the country, totaling about 91 km² (see Annex I).

2.2 Rivers, Floodplains and Swamps

The Niger River drainage covers most of the hinterland of Nigeria. Two main arms, the Niger itself (which flows for about 1 300 km through the country) and the Benue (1 440 km long) are joined by several major tributaries such as the Sokoto, the Gongola, the Kaduna and the Anambra Rivers. The main channels of the Niger and Benue Rivers are flanked by extensive floodplains: 3 000 and 1 810 km² respectively, at peak floods.

The main Nigerian tributaries to these rivers also have extensive floodplain systems. Total inland floodplain area in Nigeria reaches 5 150 km². The southern coastal part of Nigeria is drained by a series of shorter rivers, principal among which are the Ogun, the Oshun (267 km) and the Cross Rivers.

2.3 Reservoirs

One major reservoir has been formed on the Niger River behind Kainji Dam. Kainji Reservoir covers a maximum area of 1 270 km². There is a large reservoir at Tiga on the Kano River. Other large reservoirs are in project. There are numerous small reservoirs, totalling about 2 750 km² surface area (see Annex I).

Fig. 1. MAP OF NIGERIA

Table 1. SURFACE AREA OF MAJOR WATER BODIES IN NIGERIA
(Ita, et al., 1985)

2.4 Coastal Lagoons

There is a very extensive lagoon system running parallel to the coast in western Nigeria. This consists of three main elements: (a) the Badagri Creek which carries excess flood water from the Ouèmè and Oshum Rivers to (b) the Lagos Lagoon, which connects through a series of creeks to (c) the Lekki Lagoon. The whole system covers over 700 km². The Niger Delta, which covers a total of 36 260 km² consists of a network of distributaries up which saline waters penetrate for a considerable distance. There are estimated to be over 15 000 km² of swamplands in the delta which are suitable for aquaculture.

2.5 Aquaculture (adapted from FAO/IFAD, 1987)

The available water surface that can be put to direct fresh water aquaculture or culture-based fisheries has been estimated at 483 406 ha. The breakdown of this area is as follows: (Ita, et al., 1985) (See Table 1)

Table 2. SURFACE AREA OF RESERVOIRS/LAKES BY STATE
(Ita, et al., 1985)*

* Ita, et al., 1985, give a comprehensive list of all lakes, reservoirs and ponds, including name, surface area, location and ownership for each. See Annex I for checklist of lakes and reservoirs.

3. FISHERY PRODUCTION/POTENTIAL

3.1 Fish production and per caput supply

Table 3. FISH PRODUCTION AND PER CAPUT SUPPLY - Nigeria, 1970–1987

* National estimates
¹ Source: FAO
² Source: FAO Fisheries Department FISHDAB (FAO estimates; *National estimates)
Note: (FAO Yearbook Fisheries Statistics, Vol. 62, 1986): Nigeria data to be used with caution, as problems have been noted concerning representative nature of catch assessment survey.
³ included in “Inland capture” if not specified
⁴ - = data not available

3.2 Inland catch range and potential yield

Table 4. INLAND CATCH RANGE AND POTENTIAL YIELD

* included in “Other Rivers”
** No information available for Reservoirs Asejire, Eleiyele, Eruwa/Igboora, Ogbomosho, Oyo (Erelu), Shaki and Tiga.
¹ see sources in text
² Welcomme, 1979
³ excluding Niger River Delta (Rivers State), see Table 8.

4. STATE OF THE FISHERY

4.1 Yield

Because of the widely disparate estimates of production it is useful to examine the individual fisheries within Nigeria in some detail.

1. Lake Chad
   According to the latest (1985) estimates of the catch of the Lake Chad fishery, a total catch of 22 000 t is landed in Nigeria (at Baga). (Sagua, 1986)

2. Niger and Benue Rivers
   FAO/UN (1970) estimates the catch of these rivers without the delta at 13 450 and 9 570 t, respectively, for a total of 23 000 t. There is no doubt that a part of this has been lost with the closing of the Kainji Dam which controlled the flood of the Niger River downstream of the dam (Welcome, 1979). More recent data are not available.

3. Niger Delta
   There are about 15 000 km² of floodplains and swamps in the delta. These may yield about 40 kg/ha (figure based on mean performance of a sample of African floodplains), equivalent to 60 000 t (Welcomme, 1979). Official catch estimate reached 19 000 t in 1980.

4. Other rivers
   Production from these is uncertain, but is estimated by Nigerian authorities at 45 000 t; this is possibly a high estimate, and 10 000 t would seem more realistic (Welcomme, 1979).

5. Kainji Reservoir
   The catch from this reservoir (from 1969 to 1972) rose to over 10 000 t and then dropped to about one-half this weight as the tropic upsurge phase ended. The reservoir seems then to have reached a balance between catch and potential yield.

6. Coastal lagoons
   The coastal lagoons cover about 750 km² and, at a mean yield of 86 kg/ha, an annual catch of 6 450 t is possible (Kapetsky, 1981b).

7. Aquaculture (adapted from FAO/IFAD, 1987)
   Recent (1984–1986) FAO estimates for aquaculture give an annual production varying between 5 500 and 7 750 t.

   Peasant-scale fish farming has been practised in various forms in Nigeria for many years but it does not at present play a significant role in the national economy, as most ponds/farms are poorly managed, producing below their optimum capacity.

   The major species presently cultivated are Oreochromis niloticus, Cyprinus carpio, Clarias gariepinus (syn: lazera), Heterobranchus bidorsalis, Heterotis niloticus and Gymnarchus niloticus. Farmers' preferences are for Clarias, Heterobranchus, carp and Oreochromis, in that order.

   According to official statistics, production of farm fish in Nigeria was 20 476 t in 1983 and 22 011 t in 1984; 95% of this came from fresh water aquaculture. The production for 1985 was officially estimated at 22 000 t. Area under cultivation was given as 5 641 ha in 1983 and 7 179 ha in 1984. Average production was 2.5–3 t/ha/yr. These figures are significantly greater than those for 1975 when there were 1 000 ha, and average production was 750–1 000 kg/ha/yr (Dada, 1976). Exact production figures are not available, but it is understood that actual production was less, reaching about 5 500 t in 1986 (FAO estimates).

Pending updated and reliable catch data, it seems reasonable to estimate the total annual yield of Nigerian inland waters at between 110 000 and 125 000 t.

4.2 Factors influencing yield

As northern Nigeria lies within the Sahelian Belt, there are very strong climatic effects on the size of water bodies and the flow of rivers. Considerable year-to-year variations can therefore be expected due to rainfall fluctuations. The fishery in Lake Chad, for example, depends directly on the lake's size. During drought years Lake Chad may dry up in Nigeria, with a corresponding loss of fish to the country. Another problem of Lake Chad fishery is the invasion of swamp vegetation, leaving little open water surface (Wilder, 1981).

Nigeria is one of the most advanced countries in Africa and is pursuing an active policy for agricultural and industrial development. Far-reaching environmental changes are therefore to be anticipated, with consequent losses in natural production. For example, heavy domestic and industrial wastes have already caused an eutrophication and pollution in the coastal lagoons.

4.3 Future development possibilities

There is little hope of any great increase in production from the natural waters of the country; indeed, as development for other purposes proceeds, some decline in catch from the capture fisheries is to be anticipated. On the other hand, there is a good prospect of expansion of aquaculture into the very large areas available, especially in the residual pools of the floodplain and in the delta (Welcomme, 1979).

Stocking the numerous reservoirs scattered throughout the country may increase the fish production, but Ita, et al. (1985) noticed that, as the primary objective of such reservoirs is domestic water supply, care should be taken to prevent overstocking - particularly since fertilization of these reservoirs might lead to eutrophication and hence to water pollution. Stocking should therefore be limited to the natural carrying capacity of the reservoir in question.

Lake Kainji has already reached its maximum sustainable yield level; therefore any increase of catch effort is not recommended. The heavily populated and fished coastal lagoons and rivers seem also to be close to the limit of overfishing. However, a precise estimation of the potential yield of the inland waters would permit clearer decisions on how to increase the production.

5. KEY BIBLIOGRAPHY

Lake Chad: Leveque, 1987b
Lake Kainji Reservoir: Entz, 1984
Coastal Lagoons: Dufour, 1987

6. WATER BODIES DIRECTORY (see also Annex 1)

LAKE CHAD
(International water)

Fig. 2. LAKE CHAD
(Welcomme, 1972)

Fig. 3. RIVERS AND LAKES OF THE CHAD BASIN
(Welcomme, 1972)

Table 5. CHEMICAL COMPOSITION OF WATERS DURING “NORMAL” CHAD PERIOD IN MAIN LAKE ZONES
(cited in Leveque, 1987)

Values are in meq/l when not otherwise specified.
Values between parentheses () are approximate and deducted from evaporation experiments.

Table 6. FISH PRODUCTION FROM LAKE CHAD*

* Production figures obtained from road traffic census of dried fish at entry to Maiduguri: Baga and N'Djamena from July 1969 to June 1977 (original data after Stauch, 1977) in fresh weight equivalent.

Table 7. PRODUCTION FROM LAKE CHAD* (Baga, 1978–85)

¹ Source: Federal Department of Fisheries, Lagos
² Baga figure multiplied by 100/70.
* Production figures obtained from road traffic census of processed fish at entry to Maiduguri: Baga, from 1978 to 1985, in fresh weight equivalent (conversion factor of 4.5). (Sagua, 1986)

Potential annual yield:

• 100–120 kg/ha (Durand, 1980)
• 80–100 kg/ha (in “normal” 20 000 km² Chad: 160 000 t to 200 000 t/yr) (Van der Meeren, 1980)
• 70 000 t/yr max. sustainable yield, entire lake (Moses, 1982)
• 41 250–55 000 t in Nigerian waters (Ajayi & Talabi, 1984)

BENUE RIVER AND FLOODPLAIN
(International waters)

CROSS RIVER
(International water)

KADUNA RIVER

KANO RIVER

NIGER RIVER AND FLOODPLAIN
(International water)

Potential annual yield: 10 000 – 20 000 t from the Delta (Ssentongo et al., 1983)

Fig. 4. RIVERS AND LAKES OF THE NIGER-BENUE SYSTEM
(Welcomme, 1972)

Table 8. ESTIMATED AREA, ANNUAL CATCH AND POTENTIAL ANNUAL YIELD OF MAJOR LAGOONS, ESTUARIES AND RIVERS (LOWER SECTORS FRINGED BY MANGROVE, INCLUDING NIGER DELTA)
(after Ssentongo, et al., 1983)

¹ Nduaguba, 1983
² Based on records of Federal Department of Fisheries, Lagos
³ Considering the maximum potential yield of 6 000 t, the official catch estimate (32 631 t) seems overevaluated. Instead, an estimated catch equivalent to the maximum potential yield (6 000 t) is proposed.
⁴ Rivers State is here considered as the “Niger Delta”.

OSHUN RIVER

OUEME RIVER AND FLOODPLAIN
(International water)

SOKOTO RIVER
(International water)

ASEJIRE RESERVOIR

ELEIYELE RESERVOIR

ERUWA/IGBOORA RESERVOIR

I.I.T.A. RESERVOIR

KAINJI RESERVOIR

Potential annual yield: 4 500 and 6 000 t (Ita, 1984). (See also Entz, 1984, for a synthesis of known data/bibliography on Kainji up to 1984).

Fig. 5 LAKE KAINJI
(Welcomme, 1972)

MASUGA RESERVOIR

OGBOMOSHO RESERVOIR

OYO (ERELU) RESERVOIR

SHAKI RESERVOIR

TIGA RESERVOIR

LAGOS LAGOON

LEKKI LAGOON

OGUN LAGOON

7. BIBLIOGRAPHY

Ajayi & Talabi, 1984
Balon & Coche, 1974
Blache et al., 1964
Carmouze, 1976
Dada, 1976
Daget, 1954; 1957
Dufour, 1987
Durand, 1980
Dussart, 1969
Egborge, 1971
Entz, 1984
FAO/IFAD, 1987
FAO/UN, 1962; 1970; 1971
Gac, 1980
Henderson, 1973
Holden & Green, 1960
Imevbore, 1975
Ita, 1984
Ita, et al., 1985
Kapetsky, 1981b
Kapetsky & Petr, 1984
Lèvêque, 1987b
Marshall, 1984
Moses, 1982
Nduaguba, 1983
Otobo, 1979
Raimondo, 1975
Sagua, 1986
Ssentongo et al., 1983
Stauch, 1966; 1977
Van der Meeren, 1980
Welcomme, 1972; 1979; 1985
White, 1965
Wilder, 1981