SIFRA BOOK 2
1. GEOGRAPHY AND CLIMATE (Welcomme, 1979)
Benin (with a surface area of 110 620 km2) is divided into four natural regions:
The coastal region of the country is hot and humid with a moderately even temperature throughout the year. There are two rainy seasons, a major rain from March to June, and a minor one peaking in October. In the north the country becomes more arid, with a cool period in December and January and a hot period between March and June. Rainfall is concentrated into one season between July and October.
Benin is an agricultural country. The south concentrates on plantations of oil palm; to the north the main crops are maize and cotton. Cattle are abundant, particularly on the floodplains of the Niger in the north and the Ouèmè in the south. There is a considerable amount of drawdown agriculture on the floodplains in the south and rice cultivation has been introduced recently in the Ouèmè.
2. HYDROGRAPHY (after Welcomme, 1979; and Balarin, 1984a)
2.1 Lakes
Benin has over 330 km2 surface area of lakes and lagoons. There are several groups of lakes associated with the floodplains of the south-flowing rivers. On the Ouèmè there are Lakes Azilli and Cele and on the Mono there are about six lakes, but siltation and other changes due to management of this basin are altering their characteristics very rapidly.
2.2 Rivers, Floodplains and Swamps (see Fig. 1 and Table 1)
Hydrologically the country can be divided into five main drainage areas:
Fig. 1. WATER RESOURCES AND FLOW OF RIVERS IN BENIN
(Adam & Boko, 1983)
Table 1. MAIN CHARACTERISTICS OF WATER BODIES
REF. Fig. 1 | River basin | Main tributaries | Surface area '000 km2 | Length km a | Total volume discharge 109m3 | Flow m3/sec b | Lakes, Lagoons, Floodplains |
1 | MONO | Mono | 100 | 0–300 | Lagoon Grand Popo (15 km2) | ||
2 | COUFFO | Couffo | 190 | Lake Ahèmè (85 km2) | |||
Lake Toho (15 km2) | |||||||
3 | OUEME | Ouèmè | 23.6 | 510 | 5.2 | 10–900 (x=167) | Floodplain (22 km2) |
Lake Nokouè (150 km2) | |||||||
Zou | 150 | 0–110 | Lagoon Porto Novo (35 km2) | ||||
Okpara | 9.6 | 200 | 0–610 | Quidah (40 km2) (Floodplains = 1 000 km2) c | |||
4 | NIGER | Niger | 38.0 | 120 | 300–2100 | Floodplains (275 km2) c | |
Mekrou | 10.6 | 410 | 1.40 | (x=45) | |||
Alibori | 13.6 | 338 | 1.24 | 0–200 (x=40) | |||
Sota | 13.65 | 250 | 1.86 | (x=60) | |||
5 | VOLTA | Pendjari | 380 | 2.5 | 0–400 (x=81) | ||
Koumongou | |||||||
Keran |
a FAO, 1977
b Adam & Boko, 1983
c Other lakes: Tobadjii (400 ha)
Dahounta (40 ha)
Djetoue (20 ha)
Dati (70 ha)
Azilli (200 ha)
Cele (200 ha)
2.3 Reservoirs
Given the seasonal drought, several dams had to be built for water storage. Figure 1 shows the location of the existing and projected reservoirs. At present, however, there are no major reservoirs in the country, although there are several small cattle dams in the north.
2.4 Coastal Lagoons
By far the most important bodies of water in the country are the brackish-water coastal lagoons which are contiguous with the whole lagoon system of the West African coast. There are two major lagoons: Nokoue and Porto Novo which together cover about 147 km2 and are separated only by the numerous channels of the deltaic fan of the Oueme River; and Aheme Lagoon, which covers 85 km2. Smaller lagoon systems covering about 28 km2 connect the major bodies of water with the sea, and run parallel to the coast behind the dune systems. (See Fig. 2)
2.5 Aquaculture
Most of the existing ponds, built during the colonial period, have been abandoned. In 1984 there were 113–133 ponds in activity in the country, among them 55 in Godoumey, with a total surface area of 5.4 ha.
3. FISHERY PRODUCTION/POTENTIAL
3.1 Fish production and per caput supply
Table 2. FISH PRODUCTION AND PER CAPUT SUPPLY - Benin, 1970–1987
Nominal Domestic Production (including exports) (t) 2 | Nominal Consumer Supply (including exports) (kg/person) | ||||||||
Year | Population '000 1 | Inland capture | Aquaculture 3 | Marine capture 6 | Total | Inland capture | Aquaculture 3 | Marine capture | Total |
1970 | 2 708 | 23 000 | - 4 | 8 500 | 31 500 | 8.5 | - | 3.1 | 11.6 |
1971 | 2 771 | 22 500 | - | 10 400 | 32 900 | 8.1 | - | 3.7 | 11.8 |
1972 | 2 837 | 22 500 | - | 10 400 | 32 900 | 7.9 | - | 3.7 | 11.6 |
1973 | 2 904 | 20 400 | - | 8 700 | 29 100 | 7.0 | - | 3.0 | 10.0 |
1974 | 2 972 | 20 300 | - | 7 502 | 27 802 | 6.8 | - | 2.5 | 9.3 |
1975 | 3 042 | 20 260 | - | 5 673 | 25 933 | 6.7 | - | 1.8 | 8.5 |
1976 | 3 127 | 20 550 | - | 4 954 | 25 504 | 6.6 | - | 1.6 | 8.2 |
1977 | 3 215 | 20 550 | - | 4 378 | 24 928 | 6.4 | - | 1.4 | 7.8 |
1978 | 3 306 | 20 600 | - | 4 852 | 25 452 | 6.2 | - | 1.5 | 7.7 |
1979 | 3 399 | 31 800 | - | 3 900 | 35 700 | 9.4 | - | 1.1 | 10.5 |
1980 | 3 494 | 34 200 | - | 3 632 | 37 832 | 9.8 | - | 1.0 | 10.8 |
1981 | 3 599 | 34 200 | - | 3 568 | 37 768 | 9.5 | - | 1.0 | 10.5 |
1982 | 3 707 | 33 991 | 9 5 | 3 521 | 37 521 | 9.2 | 0.002 | 0.9 | 10.1 |
1983 | 3 818 | 30 991 | 9 5 | 3 628 | 34 628 | 8.1 | 0.002 | 1.0 | 9.1 |
1984 | 3 932 | 31 385 | 15 5 | 3 890 | 35 290 | 8.0 | 0.004 | 1.0 | 9.0 |
1985 | 4 050 | 29 989 | 11 5 | 8 686 | 38 686 | 7.4 | 0.003 | 2.1 | 9.5 |
1986 | 4 178 | 29 985 | 15 5 | 8 744 | 38 744 | 7.2 | 0.004 | 2.1 | 9.3 |
1987 | 4 310 | 31 973 | 14 5 | 9 916 | 41 903 | 7.4 | 0.003 | 2.3 | 9.7 |
1 Source: FAO
2 Source: FAO Fisheries Department FISHDAB
Data for inland fisheries to be used with caution as no regular catch assessment surveys undertaken. Marine catches by Beninese canoes considerably greater than catches landed in Benin as many Beninese canoes operate from beaches in Cameroon, Congo and Gabon. Catches by these canoes included in totals for respective countries.
3 included in “Inland capture” if not specified
4 - = data not available
5 Vincke, 1989, pers. comm.
6 From 1980 to 1983, marine exports were as follows: 1980: 23 t; 1981: 104 t; 1982: 57 t; 1983: 163 t.
Fig. 2. LAGOONS OF BENIN
(Weigel, 1985)
3.2 Inland catch range and potential yield
Table 3
Water body | Period | Annual catch range (t) 4 | Potential annual yield (t) |
Lakes | |||
Azilli | 1958–59 | 446 | - |
Cele | 1962 | 100 | - |
Togadji | 1955 | 12 | - |
No data available for Lakes Dahounta, Dati, and Djetoue | |||
Rivers | - | ||
Mono | 1970 | 533 | - |
Niger and Floodplain | 1959 | 3 000 | 1 200–3 000 1 |
1976 | 2 046 | ||
Pendjari | 1969 | 140 | 100–600 1 |
1976 | 580 | - | |
Ouèmè and Floodplain | 1959 | 9 000 | - |
1976 | 5 700 | ||
Lagoons | |||
Aheme | 1959 | 9 060 | 5 000–9 000 1 |
1976 | 5 200 | ||
Grand Popo/Ouidah Complex | 1969 | 610 | - |
Nokoue and Porto Novo | 1959 | 16 000 | 6 000–16 000 1 |
1976 | 5 025 | ||
Toho and Floodplain | 1969 | 72 | - |
No data available for Cotonou Lagoon | |||
Total lakes and lagoons | - | - | 15 000 2–20 000 3 |
Total floodplains | - | - | 10 000 3 |
Total rivers | - | - | 3 000 3 |
Total annual yield: 20 000–34 000 t (see section 4.1) | |||
Potential annual yield: 28 000–33 000 t (MPSAE, 1983; MFEEP, 1982) |
Sources:
1 FAO (1977)
2 MPSAE (1983)
3 MFEEP (1982)
4 See text
4. STATE OF THE FISHERY
(adapted and updated from Welcomme, 1979; and Balarin, 1984a)
4.1 Yield
The figures given in Table 2 indicate an almost steady production from the inland waters of Benin of 30 000–34 000 t/yr for the period 1980–1987, although Balarin's (1984a) estimate of the current inland catches is lower (20 000–30 000 t/yr). However, the catches were higher in the late 1950's and in the 1960's (38 288 t in 1959), before the decline of the 1970's (average: 20 000 t from 1970 to 1978).
Aquaculture production remains low (14 t in 1987) (Vincke, 1989 pers. comm.):
Species | 1982 | 1983 | 1984 | 1985 | 1986 | 1987 |
Oreochromis spp. | 9 t | 9 t | 15 t | 11 t | 15 t | 14 t |
4.2 Factors influencing yield
Losses have occurred in the four main fisheries of the country for a variety of reasons. In the Niger River the decline was provoked, at least intially, by the failure of the main markets for fish from this region. However, the Sahelian drought also exercised a serious effect. Unfavourable conditions have continued with erratic and poor flooding in most years and the decline of the Niger River Fishery has continued.
In the Ouèmè basin, long and intensive exploitation affected the fishery; the catch dropped from about 10 000 t/yr prior to 1960 to about 6 000 t/yr in 1976. The fact that over-exploitation was responsible is indicated by the disappearance of the larger species of fish and decline in the mean size of the fish caught. Changes in salinity of the lower reaches of the river, caused by the permanent opening of Nokoue Lagoon to the sea, have also been implicated, but do not satisfactorily explain the changes in catch that have occurred.
There is, however, no doubt that changes in salinity were responsible for the collapse of the most important fishery on the lagoon. Thus, the acadja fishery used extensive areas of brush parks to rear and capture fish, giving yields as high as 10 t/ha of park in the late 1950's. Subsequently, invasion of the lagoon by teredo worms destroyed or rendered uneconomic large areas of parks, and placed greater fishing pressure on the other fish stocks which, in their turn, collapsed. Investigations in 1981 showed that the fishery recovered to a certain extent following the installation of a weir across the mouth of the channel. The fall in catch in Aheme Lagoon from 9 000 t in 1959 to about 5 000 t in 1976 coincides with the removal of acadjas from that lagoon for political reasons.
4.3 Future development possibilities
The history of the fisheries of Benin represents a classical example of past mismanagement of various types. Nevertheless, future possibilities could be moderately good. A return to a pluvial phase in the Sahel could increase production from the Niger river to its previous high level, if suitable markets for the products can be found.
Previous production levels could possibly be restored in the lagoons. In Aheme Lagoon, the simple reintroduction of acadjas in a planned fashion would probably bring immediate results. In Nokoue Lagoon the need to control the penetration of sea waters is paramount, and the recent construction of a barrage across the channel at Cotonou blocking the ingress of sea water may permit the lagoon to be used as a vast fish culture pond.
In the Ouèmè, however, the prospects are somewhat bleak. The fishery is already over-exploited and the valley is densely populated so it is difficult to see that the pressure will be relieved. Furthermore, the floodplain of the Ouèmè is now being increasingly used for rice culture and the drain-in fish ponds, which contributed much to the fishery, are being abandoned. There will almost certainly be an attempt to control the Ouèmè floods with an upstream dam in the future, and the floodplain fishery will be lost as a consequence (although of course a reservoir fishery resource will be created). Apart from the natural water bodies, considerable increases in production of fish from Benin can be foreseen with the successful introduction of brackishwater aquaculture into the coastal belt.
Present inland fisheries potential annual yield has been estimated at 28 000–33 000 t/yr (MFEEP, 1982; MPSAE, 1983).
5. KEY BIBLIOGRAPHY
Balarin, 1984a
Weigel, 1985 (Lagoons)
6. WATER BODIES DIRECTORY
Lakes | ||
Azilli | Dahounta | Djetoue |
Cele | Dati | Togbadji |
Rivers | ||
Mono | Niger (and Floodplain) | Oti/Pendjari |
Ouèmè (and Floodplain) | ||
Lagoons | ||
Aheme | Grand Popo/Ouidah Complex | Toho/Floodplain |
Cotonou | Nokoue | |
Djonou | Porto Novo |
LAKE AZILLI
Geographical data | |
Location: | Benin |
Surface area: | 2 km2 (plus 3.5 km2 of associated swamps) |
Major inflowing river: | Ouèmè |
Outflowing river: | Ouèmè |
Fisheries data | |
Total annual catch: | 446 t in 1958–59 |
LAKE CELE
Geographical data | |
Location: | Benin |
Surface area: | 2 km2 |
Major inflowing river: | Ouèmè |
Outflowing river: | Ouèmè |
Fisheries data | |
Total annual catch: | 100 t in 1962 |
LAKE DAHOUNTA
Geographical data | |
Location: | Benin |
Surface area: | 0.40 km2 (but 1.5 km2 in 1955) |
LAKE DATI
Geographical data | |
Location: | Benin |
Surface area: | 0.70 km2 |
LAKE DJETOUE
Geographical data | |
Location: | Benin |
Surface area: | 0.20 km2 (but 3 km2 in 1955) |
Fisheries data | |
No. of fishing boats: | 2 in 1969 |
LAKE TOGBADJI
Geographical data | |
Location: | Benin |
Surface area: | 4 km2 |
Fisheries data | |
Total annual catch: | 12 t in 1955 |
MONO RIVER
(International water)
Geographical data | |
Source: | Faille de Bafilo, Togo |
Altitude: | 420 m |
Total length: | 360 km |
Drainage area: | 22 000 km2 |
Countries traversed: Benin, Togo | |
Discharges to: | Atlantic Ocean, Grand Popo, Benin - 5° 49'N; 2° 5'E |
Volume of discharge at mouth: 710 m3/sec (max); 380 m3/sec (mean in September) | |
Flood regime: | peak flow in September |
Special features: | floodplain along lower course |
Fisheries data | |
Total annual catch: | in Benin, 533 t in 1970 |
NIGER RIVER AND FLOODPLAIN
(International water)
Geographical data (Welcomme, 1972, 1985) (See Fig. 3) | |
Source: | Fouta Djallon, Guinea |
Altitude: | 1 000 m |
Total length: | 4 183 km |
Drainage area: | 1 125 000 km2, including the Benue |
Area of water: |
Floodplain (Niger River) | At peak flood (km2) | At low water (km2) | Floodplain area (km2) | Authority | |
Central delta (Mali) | 20 000 | 3 877 | 16 123 | Raimondo, 1975 | |
Fringing plains: | |||||
Niger | 907 | 270 | 637 | FAO/UN, 1971 | |
Benin | 274 | 32 | 242 | FAO/UN, 1970 | |
Nigeria | 4 800 | 1 800 | 3 000 | FAO/UN, 1970 |
Countries traversed: | Niger River: Benin, Guinea, Mali, Niger, Nigeria Tributaries: Burkina Faso, Cote d'Ivoire |
Major tributaries: | Bani (Mali); Alibori, Mekrou, Sota (Benin); Beni (Burkina Faso); Bagoue (Cote d'Ivoire); Sokoto, Banue/Benouè (Nigeria) |
Discharges to: | Atlantic Ocean - 4° 22'N; 5° 27'–7° 14'E |
Volume of discharge at mouth: 6 100 m3/sec | |
Suspended silt load: | 5 050 000 t/yr |
Flood regime: | At the Nigerian border there are two floods, one with a peak in January-February, originating from Guinea; the other in August-October, originating locally. |
Special features: | Internal delta and lakes (Mali), Kainji dam and reservoir (Nigeria). Delta at mouth. Several floodplains. |
Physical and chemical data | |
Conductivity: | K20: 31 μ S/cm (upper course) (Daget, 1957) |
Temperature: | 19–30°C (upper course) (Daget, 1957) |
pH: | 7.2 (upper course) (Daget, 1957) |
6.7–6.8 (middle course) (FAO/UN, 1962) |
Ionic composition:
At level of central delta (Daget, 1957) | |
Na | 2.99 mg/l |
K | 1.96 mg/l |
Ca | 4.01 mg/l |
Mg | - |
Cl | 1.07 mg/l |
SO4 | - |
At level of Kainji dam (White, 1965) | |
Ca | 3.45–5.98 mg/l |
Mg | 1.18–2.69 mg/l |
Na | 2.25–5.80 mg/l |
HCO3 | 24.64–38.67 mg/l |
SO4 | 0–1.73 mg/l |
Cl | trace-1.28 mg/l |
NO3 | 1.43–6.29 μg/l |
PO4 | 0.483–3.102 μg/l |
Fig. 3. RIVERS AND LAKES OF THE NIGER-BENUE SYSTEM
(Welcomme, 1972)
Fisheries data
No. of fish species: 135 (Daget, 1954)
No. of fishermen: 3 000 in Benin
Total annual catch:
Niger River in 1966, inland waters (excluding Niger Delta): | ||
Benin | 1 000 t | (FAO/UN, 1971) |
Mali | 90 000 t | |
Niger | 9 696 t | (FAO/UN, 1971) |
Nigeria | 13 450 t | (FAO/UN, 1970) in river |
Total | 114 146 t | |
in Benin: | 3 000 t | (1959); |
1 173 t | (1969); | |
2 045 t | (1976) |
Potential annual yield: 1 200–3 000 t in Benin (FAO, 1977)
OTI/PENDJARI RIVER
(International water)
Geographical data | |
Source: | Atakora Mountains of Benin |
Altitude: | 640 m asl |
Total length: | 900 km |
Drainage area: | 72 900 km2 |
Countries traversed: | Benin, Burkina Faso, Togo, Ghana |
Discharges to: | Volta Reservoir |
Volume of discharge at mouth: 500 m3/sec | |
Physical and chemical data | |
pH: | 6.4–6.7 |
Fisheries data
Total annual catch in Benin:
Year | Total catch (t) | No. of fishermen | No. of boats |
1962 | 300 | - | - |
1963–67 | - | - | - |
1968 | 179 | 65 | 20 |
1969 | 140 | - | - |
1970–75 | - | - | - |
1976 | 580 | - | - |
Potential annual yield: 100–600 t in Benin (FAO, 1977)
OUEME RIVER AND FLOODPLAIN
(International water)
Geographical data | |
Source: | Atakora Massif, Benin |
Altitude: | 600 m |
Total length: | 700 km |
Drainage area: | 40 150 km2 |
Countries traversed: | Benin, Nigeria |
Major tributaries: | Okpara, Zou |
Discharges to: | Nokone, Porto Novo and Lagos Lagoons |
Flood regime: | floods last from July to November (peak in August) |
Special features: | in Benin, Lakes Azilli (2 km2 plus 3.5 km2 of associated swamp) and Cele along middle course and floodplain (2 000 km2) along lower course with Lakes Hlan (1.90 km2), Ouovi (0.20 km2), Tossahoue (0.64 km2), Newe (0.76 km2) and 12 smaller lakes (1.8 km2 combined). In Nigeria, an extensive deltaic floodplain at mouth (1 000 km2). |
Physical and chemical data | |
Conductivity: | K20 60 μ S/cm (Welcomme, 1985) |
Fisheries data
No. of fish species: 60 (Welcomme, 1972)
Total annual catch and effort: in Benin
Year | Total catch (t) | |
1955 | 10 000 | |
1956 | - | |
1957 | 10 400 | |
1958 | - | |
1959 | 9 000 | (Welcomme, 1979) |
1960–67 | - | |
1968–69 | 6 484 | |
1970–75 | - | |
1976 | 5 700 | (Welcomme, 1979) |
AHEME LAGOON
Geographical data | |
Location: | Benin - 6° 27'N; 1° 58'E |
Surface area: | 85 km2 |
Depth: | 3 m (max); 1.2 m (mean) |
Max. length: | 25 km |
Max. width: | 4 km |
Major inflowing river: | Couffo |
Outflowing river: | Couffo to the Grand Popo Lagoon, which connects Aheme Lagoon, Togo Lagoon and the Mono River |
Physical and chemical data | |
Salinity: | 1–36 ‰ |
Fisheries data
Total annual catch and effort:
Year | Total catch (t) | No.of fishermen | |
1959 | 9 060 | - | (Welcomme, 1979) |
1960–61 | - | - | |
1962 | 3 000 | 8 200 | |
1963–68 | - | - | |
1969–70 | 8 151 | 10 000 | |
1971–75 | - | - | |
1976 | 5 200 | - | (Welcomme, 1979) |
Potential annual yield: 5 000–9 000 t (FAO, 1977)
COTONOU LAGOON
Geographical data | |
Location: | Benin |
Surface area: | 1.60 km2 |
Max. length: | 4.5 km |
DJONOU LAGOON
Geographical data | |
Location: | Benin |
GRAND POPO/OUIDAH LAGOON COMPLEX
Geographical data | |
Location: | Benin - 6° 18'N; 2° 0'E |
Surface area: | 12 km2 (consists of Grand Popo and Ouidah Lagoons and interconnecting canals) |
Max. length: | 60 km |
Max. width: | 0.2 km |
Major inflowing rivers: | Couffo (from Aheme Lagoon), Mono |
Outflow: | Bouche du Roi canal to Atlantic Ocean |
Special features: | connected to Togo Lagoon in the west and Nokone Lagoon in the east (to the latter via a swampy prolongation). Acadjas present in lagoon complex and also inflowing Couffo River (= Aho River). |
Fisheries data | |
Total annual catch: | 610 t in 1969 |
Fig. 4. NOKOUE AND THE PORTO NOVO LAGOONS
(Weigel, 1985)
NOKOUE LAGOON
Geographical data | |
Location: | Benin - 6° 25'N; 2° 27'E (see Fig. 4) |
Surface area: | 139.5 km2 |
Max. length: | 19 km |
Max. width: | 12 km |
Major inflowing rivers: | Ouèmè, Zou |
Outflow: | Coknore Canal to Atlantic Ocean |
Special features: | extensive acadjas (brush parks) present |
Fisheries data
Total annual catch and effort:
Year | Total catch (t) | No. of fishermen |
1959 | 14 420 | - |
1960–63 | - | - |
1964 | 9 300* | - |
1965 | 9 500 | 11 000 |
1966–68 | - | - |
1969 | 5 238 | - |
1970–75 | - | - |
1976 | 5 025 | - |
* (includes Porto Novo Lagoon)
Potential annual yield: 6 000–16 000 t - including Porto Novo Lagoon (FAO, 1977)
PORTO NOVO LAGOON
Geographical data | |
Location: | Benin - 6° 27'N; 2° 36'E (see Fig. 4) |
Surface area: | 17.52 km2 |
Max. length: | 6 km |
Max. width: | 4 km |
Major inflowing river: | Ouèmè |
Outflowing river: | Ouèmè to Lagos Lagoon in Nigeria |
Fisheries data (*includes Nokoue Lagoon) | |
Total annual catch: | 1 000 t (1959); *9 300 t (1964); *5 025 t (1976) |
Potential annual yield: | *6 000–16 000 t (FAO, 1977) |
TOHO LAGOON/FLOODPLAIN
Geographical data | |
Location: | Benin |
Surface area: | 16 km2 (of which 6 km2 are seasonally inundated swamps) |
Fisheries data
Total annual catch and effort:
Year | Total catch (t) | No.of fishermen | No.of boats |
1969 | 72 | 97 | 30 |
7. BIBLIOGRAPHY
Adam & Boko, 1983
Balarin, 1984a
Daget, 1954; 1957
FAO, 1977
FAO/UN, 1962; 1970; 1971
MFEEP, 1982a,b
MPSAE, 1983
Raimondo, 1975
Weigel, 1985
Welcome, 1972; 1979; 1985
White, 1965