MANZALAH LAGOON
Geographical data (see Fig. 9) | |
(*cited in Lemoalle, 1987) | |
Location: | Egypt - 31° 3'–31° 32'N; 31° 45'–32° 17'E |
Altitude: | 0–0.6 m asl |
Surface area: | *900 km2 in 1980 (open water) |
Depth: | 1 m (mean) |
Max. length: | *64 km |
Max. width: | *49 km |
Inflow: | *numerous drains, the most important being Bahr el Bakar (1.7 109m3/yr) and Hadous (3.3 109m3/yr). |
Outflow: | *several connections to the sea (main: El Gamil). |
Special features: | *numerous islands, enclosures (143 km2) and fish farms. Salinity range: 2–15 g/l. Mean salinity decreasing due to restriction of lake-sea connections and drainage inputs. Salinity is lowest after peak drainage inflow in September and October. |
Note: (see also FAO, 1980b)
Fig. 9 MANZALAH LAGOON
(Lemoalle, 1987)
Physical and chemical data | ||
Surface temperature: 14.5° C (Jan.); 30.3° C (Aug.) | ||
Salinity: | *2.9 g/l (1987); 9 g/l (1962–63); 16.7 g/l (1921–26) | |
Oxygen: | *mean: over 5 mg/l; lower in southern sector during night. | |
Ionic composition: | mg/l | |
NO3 | 0.627 | |
PO4 | 0.129 annual mean (1979) | |
Fisheries data | ||
Fish species: | main catches: (Lemoalle, 1987) “tilapias” 85% (mainly Oreochromis niloticus); Anguilla anguilla; Mugil cephalus, Liza saliens, Clarias lazera, Bagrus bayad, Labeo niloticus, and other marine species in smaller numbers. |
Total annual catch and effort:
Year | Total catch (t) | No.of fishermen | No.of boats |
1907 | 10 343 | - | - |
1908 | 9 061 | - | - |
1909 | 12 910 | - | - |
1910 | 12 988 | - | - |
1911 | 15 170 | - | - |
1912 | 12 862 | - | - |
1913 | 11 230 | - | - |
1914 | 8 496 | - | - |
1915 | 10 466 | - | - |
1916 | 10 857 | - | - |
1917 | 15 251 | - | - |
1918 | 16 893 | - | - |
1919 | 14 971 | - | - |
1920 | 18 911 | - | - |
1921 | 10 018 | - | - |
1922 | 11 082 | - | - |
1923 | 11 292 | - | - |
1924 | 13 160 | - | - |
1925 | 11 477 | - | - |
1926 | 14 056 | - | - |
1927 | 16 306 | - | - |
1928 | 15 156 | - | - |
1929 | 11 385 | - | - |
1930 | 12 156 | - | - |
1931 | 9 742 | - | - |
1932 | 11 435 | - | - |
1933 | 12 901 | - | - |
1934 | 14 360 | - | - |
1935 | 13 502 | - | - |
1936–56 | - | - | - |
1957 | 14 164 | - | - |
1958 | 15 646 | - | - |
1959 | 11 148 | - | - |
1960 | 10 520 | - | - |
1961 | 12 070 | - | - |
1962 | 18 951 | - | - |
1963 | 20 112 | - | - |
1964 | 21 870 | - | - |
1965 | 19 321 | - | - |
1966 | 28 370 | - | - |
1967 | 25 029 | - | - |
1968 | 24 407 | - | - |
1969 | 20 596 | - | - |
1970 | 21 977 | - | - |
1971 | 20 629 | - | - |
1972 | 21 000 | - | - |
1973 | 21 000 | - | - |
1974 | 20 000 | - | - |
1975 | 21 745 | - | - |
1976 | 26 380 | 5 500 | 2 922 |
1977 | 27 350 | - | - |
1978 | 27 350 | - | - |
1979 | 39 046 | 16 133 | 3 755 |
1980 | 63 330 | - | - |
1981 | - | - | - |
1982 | 59 000 | - | - |
not specified | - | 17 000* | 4 000* |
- | 8 340** | 2 900*** |
* (Lemoalle, 1987)
** (Shaheen et al., 1980)
*** (Ferlin, 1980)
1979–80: 40 000 t/yr (open water fisheries), plus 20 000–25 000 t/yr for howash or hoshas (enclosures and fish farms. The general evolution of the lagoon from the 1960's to 1980 revealed increased fishing with decreasing salinity and increased nutrient inputs (eutrophication) (cited in Lemoalle, 1987).
Potential annual yield:
31 000 t/yr (Balarin, 1986)
75 000 t/yr (Sadek, 1984)
140–250 kg/ha/yr (Sadek, 1984)
MARIUT LAGOON
Geographical data (see Fig. 10) | ||
(*cited in Lemoalle, 1987) | ||
Location: | Egypt, near Alexandria - 31° 5'N; 29° 54'E | |
Altitude: | -3 m | |
Surface area: | *27.3 km2 (1987), larger earlier | |
Inflow: | *drainage water (Qalaa drain) | |
Outflow: | *water pumped to the sea | |
Depth: | *0.9–1.5 m | |
Special features: | *initially an elongated lagoon with an area of 110 km2; area reduced by half between 1950 and 1980, now about 27.3 km2 for lagoon proper. The lagoon is fed by drainage as well as domestic and industrial waste water. Evidence of pesticide and heavy metals accumulation in fish. | |
Physical and chemical data | ||
Temperature: | *12.7–29.0°C (1969–1970) | |
pH: | *7.3–9.7; low pH near industrial inputs (1969–70) | |
Salinity: | 5–8% | |
Ionic composition:* | ||
Cl | 1.5–6.4 g/l (in 1960); 1.09–2.63 g/l (1969–70) | |
SO4-Si | 0.8–11.2 mg/l | |
PO4-P | 2.3–10.9 mg/l (1969–70) | |
SiO2 | 8.2–15.9 mg/l (1969–70) | |
NO3-N | 0–252 μg/l | |
NO2 | 108–659 μg/l | |
Fisheries data | ||
Fish species: | (cited in Lemoalle, 1987) | |
Main catches: | “tilapias” 77%; Clarias sp. 17% | |
No. of fishermen: | 3 140 (Shaheen et al., 1980) | |
No. of boats: | 1 050 (1976); 1 060 (1975) | |
Total annual catch: | ||
3 120 t (1972); 3 712 t (1975); | ||
17 000 t (Lemoalle, 1987) | ||
Potential annual yield: | ||
11 000–15 000 t/yr (Balarin, 1986) | ||
90– 1 400 kg/ha/yr (Sadek, 1984) |
Fig. 10. MARIUT LAGOON AND NOZHA HYDRODROME
(Lemoalle, 1987)
NOZHA HYDRODROME LAGOON
Geographical data (see Fig. 10) | ||
(*cited in Lemoalle, 1987) | ||
Location: | Egypt - 31° 12'N; 29° 58'E | |
Altitude: | *-3.6 m (bottom) | |
Surface area: | *4.8 km2 | |
Total length: | *3.3 km | |
Total width: | *2.4 km | |
Depth: | *3 m (mean) | |
Major inflowing river: Nile, by way of a feed canal (the Mahmoudia Canal) | ||
Special features: | *the Hydrodrome was created in 1939 by isolating a part of Mariut Lagoon. It is now surrounded by a concrete embankment 9 km in length, and is used as a fish farm. | |
Physical and chemical data | ||
Temperature: | 15.5°C (Jan.); 27.5°C (Sept.) | |
pH: | 7.45–8.85 | |
O2 | 6.3 to 10.7 mg/l (monthly average) | |
Ionic composition: | controlled by Nile water discharge and evaporation | |
Cl | 0.12–0.48 g/l | |
PO4 | 45–720 μg/l | |
NO2 | 12.4–52.3 μg/l | |
SiO2 | 8.2–15.9 μg/l | |
Alkalinity | 2.1–4.3 meq/l | |
Fisheries data: | not available. |
PORT FOUAD (= EL-MALLAHA) LAGOON
Geographical data (Balarin, 1986) | |
Location: | Egypt (see Fig. 3, p.40) |
Area: | 96–200 km2 |
Depth: | 0.7–12 m |
Fisheries data | |
Total annual catch: | |
150 t (1982); 300 t (1976) | |
Potential annual yield: (Sadek, 1984) | |
600 kg (37 kg/ha/yr) |
TIMSAH LAGOON
Geographical data | |
Location: | Egypt - 30° 34'N; 32° 18'E |
Surface area: | 16.8 km2 |
Max. length: | 6 km |
Max. width: | 4 km |
Inflow/Outflow: | Suez Canal. |
UM EL RISH LAGOON
Geographical data | |
Location: | Egypt - 31° 0'N; 32° 17'E |
Area: | 78 km2 |
Max. length: | 18 km |
Max. width: | 9 km |
Inflow: | drainage canal from Manzalah Lagoon |
Outflow: | to Suez Canal |
Fisheries data | |
No. of fishermen: | 459 (1979) |
No. of boats: | 255 (1979) |
Total annual catch: | 2 267 t (1979). |
7. BIBLIOGRAPHY
Ali, 1984
Atkins Land and Water Management, 1979
Balarin, 1986
Boulenger, 1907
C.A.P.M.S., 1982
Entz, 1984
FAO, 1974, 1980a, b
FAO/UNDP, 1975
Feidi, 1976
Ferlin, 1980
Hefny, 1982
Henderson, 1975
Ishak, Hamza, 1983
Kapetsky & Petr, 1984
Latif, 1984
Lemoalle, 1987
Marshall, 1984
Pisanty, 1981
Saad, 1982
Sadek, 1984
Shaheen et al., 1980
S.I.S., 1983a,b
Welcomme, 1972–1979
Wunder, 1960
1. GEOGRAPHY AND CLIMATE
(adapted from Welcomme, 1979 and Balarin, 1986)
Ethiopia has a surface area of 1 223 600 km2. More than 60 percent of the country lies above 1 000 m, with extensive plains over 2 000 m. Elevations range from 120 m below sea level in the Dallol Depression (Kobar Sink), south of Massawa, to over 4 620 m in Mount Ras Dushon, north of Lake Tana. In all, ten mountain peaks of the plateau region rise over 4 000 m. A great deal of the terrain is mountainous, rugged and deeply dissected by rivers. The southern half is bisected by the northern arm of the Rift Valley and ranges from 40 to 60 km in width, with escarpments 1 000–1 500 m high. The floor of the valley is occupied by a large number of lakes (see Fig. 2, Table 1) and the rift line forms the main river watershed.
The plateaux to the west of the rift system form the Central Highlands (2 000–2 500 m). To the east are the lower range of the Bale and Havar plateaux. The north-eastern part of the Rift Valley opens out into a delta-shaped plain, in the northern part of which lies the Dallol Depression, an area of 5 000 km2 below sea level. The Darcalli range separates these lower plains from the Red Sea. Only in a narrow coastal zone are there lowland areas below 200 m.
The climate is generally temperate on the plateau, but becomes hot and arid on the lowlands, and is desertic in the northeast and the south. On the plateau there is a short wet season from February to April, and a major rainy season from June to September.
Ethiopia is an entirely agricultural country, where intensive use of marginal lands has often caused severe erosion. Rivers are consequently highly silted. There has been little development for irrigation except along the Awash River.
2. HYDROGRAPHY
(adapted from Welcomme, 1979 and Balarin, 1986)
Aubray (1975) reports that 173 000 km2 (14%) of Ethiopia consists of swamp (4%), lakes (1%), rivers and floodplains (9%). This is much higher than the figures given by FAO (1984) for wetland (0.7%, 9 200 km2) and water body (0.5%, 6 700 km2) areas. (See Fig. 3, Table 2.)
2.1 Lakes (see Fig. 2, Table 1)
The total lake area in Ethiopia was estimated as 7 500 km2 by Aubray (1975), but the statistics listed in Table 1 show that this area may be as much as 8 800 km2.
Ethiopia is moderately well supplied with natural lakes. Lake Tana (3 500 km2, 52% of the total lakes area) is the largest lake wholly contained in Ethiopia, but a small portion of Lake Turkana and over half of Lake Abbe are also within the territory. A chain of eight small- to medium-sized lakes are situated in the Rift Valley (Lakes Abaya, Abiyata, Awasa, Chamo, Chew Bahir, Langano, Shala, Chamo and Ziway); these cover 40 percent of the lakes area.
The very high conductivity of the waters of some of these lakes shows them to be the highly saline, soda-type lakes typical of the Rift Valley.
In addition, there are numerous small, deep crater lakes. These are generally high-altitude lakes, with a mean altitude of 1 750 m; the lowest, apart from Lake Turkana, are the Abaya and Chamo lakes at about 1 250 m.
Other sizeable lakes are those associated with the Awash River (Lakes Beda, Yardi, Afambo and Gemeri) and the isolated Lake Afrera Ye'Ch'ew.
Several of the lakes have an interlinking river system.
2.2 Rivers, Floodplains and Swamps
There are nine major rivers, totalling 6 400 km with an annual discharge (MAR) of 63 billion cubic metres, of which the Blue Nile accounts for 80% (Aubray, 1975). There are six major drainage basins (see Table 2 and Fig. 3). The major systems are those of the Nile in the northwest and the Indian Ocean systems of Bale and Horor. The Red Sea rivers are mostly short and torrential. There are several closed depressions and numerous lakes associated with the Rift Valley. The largest internal drainage system is the Awash River, running northward along the Rift Valley for over 500 km before dissipating in a complex of salt lakes and marshes (Lakes Abbe and Gemeri).
The Blue Nile (Abbai) River takes its source from Lake Tana and flows for about 760 km through Ethiopia. It is torrential and steeply encased by mountains for much of its course.
The Omo River flows south from the central highlands for some 600 km and discharges into Lake Turkana through a small marshy delta. Two other rivers, the Shabale (about 900 km in Ethiopia) and the Ganale (about 500 km in Ethiopia) drain the highlands toward the south and cross the Ogaden Desert before entering Somalia.
The eastern streams and those in areas of high rainfall tend to be short, intermittent and torrential. Other rivers, such as the Abbai (Blue Nile), Baro, Omo, Webi Shebelli, Awash and Takazzi, are long and perennial. There is a great difference between discharge in the wet season (July-September) and that of the dry season. The Awash discharge, for example, previously ranged from 2 to 600 m3/s but, since the construction of the Koka Dam, now maintains a steady flow of 43 m3/s.
Available data on mean annual runoff (MAR) is summarized in Table 2. Of interest is the exceptionally high runoff shown by the Blue Nile, a characteristic of the wetter region.
The rivers are usually very deeply incised in their upper courses and their irrigation potential consequently impracticable without artificial control. There is, however, considerable scope for the construction of dams for the production of hydroelectric power and, therefore, also for water control, irrigation and fish production. None of the rivers is navigable except for the lower Baro.
In the south there is the drying Chew Bahir Lake/Swamp (Lake Stefanie), and in the northeast the Danakil Depression is characterized by swamp and salt lakes, notably the Aussa swamp, the salt Lake Abbe and the Assole Lagoon.
The Pibor and the Baso (tributaries of the Sobat River) develop a common floodplain-swamp.
Hot springs and mineral springs occur at several places within the Rift Valley, but no documentation is available.
Fig. 1. MAP OF ETHIOPIA
2.3 Reservoirs
There are two large reservoirs (Fincha and Koka) and three smaller impoundments (Zula, Legadadi and Abarda).
2.4 Coastal Lagoons
There is only one small lagoon near Bera'isole.
Numbers refer to Table 1.
Fig. 2. DISTRIBUTION OF MAJOR ETHIOPIAN LAKES AND RESERVOIRS
(Balarin, 1986)
Table 1. MORPHOLOGICAL DATA OF MAJOR LAKES AND RESERVOIRS
(adapted from Balarin, 1988)
Location. refer. Fig. 2 | Name (date constructed) | Basin/District (Basin area, km2) | Description | Present catch (t/yr) | Use * | Fish species | |||
Volume (109m3) | Area (km2) | Altitude (m) | Mean depth (m) | ||||||
1 | Lake Abaya (Margherita) | Rift Valley (17 300) | 7.9 | 1 161 | 1 285 | 7 | 100 | f | 25 |
2 | Lake Stephanie (Chew Bahir) | Rift Valley | 0–50 | ||||||
3 | Lake Tana | 28.4 | 3 500 | 1 829 | 8 | 20 | f | 20 | |
4 | Lake Zwai (Ziway) | Rift Valley (7 020) | 1.1 | 434 | 1 850 | 2.5 | 300–500 | f | 8 |
5 | Lake Langano | Rift Valley (1 600) | 3.8 | 230 | 1 585 | 17 | 1 000 | f | |
6 | Hora Abyata | Rift Valley (1 630) | 1.6 | 205 | 1 570 | 7.6 | no fishing | ||
7 | Lake Shala (crater lake) | Rift Valley (3 920) | 37 | 250–409 | 1 567 | 8.6 | unfished | ||
8 | Lake Awasa | Rift Valley (1 250) | 1.3 | 130 | 1 210–1 708 | 10.7 | 100 | f | 3 |
9 | Lake Shama (Ruspoli) (Chamo) | Rift Valley | 4.1 | 551 | 1 282 | ||||
10 | Fincha Reservoir (1971) | 0.6 | 170 | 2 215 | 7 max | p,i | |||
11 | Lake Haik (Hayk) | 0.9 | 23–35 | 1 670–2 030 | 37.4 | ||||
12 | Lake Hora | 0.2 | 1 | 1 600–1 850 | 17.5 | ||||
13 | Lake Babigata | 0.2 | 0.7 | 1 600 | 60 max | ||||
14 | Lake Aresade (Hora) | 1 029 | 1 850 | 17.5 | |||||
15 | Lake Rudolf (Turkana) | 407 | f | 37 | |||||
16 | Lake Ashenge | 20 | 2 409 | ||||||
17 | Lake Bishoftu | 85 max | |||||||
18 | Koka Reservoir (1959) | 0.01 | 255 | 1 590 | 9–14 max | 100 | f,i | 20 | |
19 | Gewane | ||||||||
20 | Abe | ||||||||
21 | Gargori |
Letters refer to Table 2.
Fig. 3. RIVER SYSTEMS OF ETHIOPIA
(Gamachu, 1977)
Table 2. MAJOR RIVER SYSTEMS AND HYDROLOGICAL ZONES
(Balarin, 1986)
Basin (Ref. Fig.2) | Major River System | Flow | Runoff | No.of fish species | ||||
Name | Length (km) | Catchment ('000 km2) | MAR (million m3) | (m3/s) | (mm) | Rainfall % | ||
Nile Basin | ||||||||
Aa | Sobat | |||||||
- Baro River | 280 | (50) | 8 | |||||
Ab | Blue Nile (Abbay) | 800–1 000 | 326.4 | 50 000 | 170–7 000 | 22 | ||
- Angar River | 4.3 | 64.8 | 469.7 | 31.3 | ||||
- Beles River | 3.5 | 36.0 | 322.3 | 26.9 | ||||
Ac | Atbara | |||||||
- Tekezze River | 610 | 4 000 | ||||||
- Angareb River | 220 | |||||||
Indian Ocean Basin | ||||||||
Ba | Juba | |||||||
- Genale Doria River | 480–860 | (200) | ||||||
Bb | Wedi Shebelle | 1 000 | 2 000 | 14 | ||||
Mereb Basin | ||||||||
C | - Mereb Gah River | 440 | (100) | |||||
Omo Basin | ||||||||
D | - Omo Ghibe River | 760 | 6 600 | 13 | ||||
Rift Valley Basin | ||||||||
Ea | Awash | 1 200 | 7.7 | 100 | 40.3 | 164.6 | 18.3 | 20 |
- Mille River | 4.3 | 6.9 | 50.1 | 10.0 | ||||
Eb | Awsa | |||||||
- Barka River | 430 | (100) | ||||||
Ec | Upper Rift | |||||||
Red Sea Basin | ||||||||
Fa | Red Sea Coast System | |||||||
Fb | Barka |
Sources: Aubray, 1975; CSO, 1980; FAO/UNDP, 1982; Gamachu, 1977; Tedla, 1973.
2.5 Aquaculture
Aquaculture development is practically non-existent and there is a confusion between fish farming and fisheries management.
In view of the absence of any form of classical aquaculture, transplantation of fish into natural water bodies is hereunder considered as a form of extensive aquaculture.
Fish farming activities consist of fish pond experiments (reported by Meskal, 1974, 1975, 1976) and the establishment of a Fisheries Research Station at Sebeta where fish are reared in ponds for subsequent transplanting into natural water bodies. Over the years considerable fish transportations have taken place under the auspice of fish farming but in reality, as these stockings were of natural water bodies, such practices are actually a part of fisheries management. Unfortunately transfers have not been adquately documented; what is known has been summarized by Tedla and Meskal (1981).
3. FISHERY PRODUCTION/POTENTIAL
3.1 Fish production and per caput supply
Table 3. FISH PRODUCTION - Ethiopia, 1970–1987
Nominal Domestic Production (including exports) (t) 2 | Nominal Consumer Supply (including imports/exports) (kg/person) | ||||||||
Year | Population '000 1 | Inland capture | Aquaculture 3 | Marine capture 4 | Total | Inland capture | Aquaculture 3 | Marine capture | Total |
1970 | 30 623 | 900 | 0 | 16 300 | 17 200 | 0.03 | 0 | 0.53 | 0.56 |
1971 | 31 327 | 300 | 0 | 18 800 | 19 100 | 0.01 | 0 | 0.60 | 0.61 |
1972 | 32 047 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.80 | 0.83 |
1973 | 32 784 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.78 | 0.81 |
1974 | 33 538 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.77 | 0.80 |
1975 | 34 309 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.75 | 0.78 |
1976 | 35 113 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.73 | 0.76 |
1977 | 35 936 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.72 | 0.75 |
1978 | 36 777 | 1 000 | 0 | 25 800 | 26 800 | 0.03 | 0 | 0.70 | 0.73 |
1979 | 37 639 | 2 800 | 0 | 0 | 2 800 | 0.07 | 0 | 0 | 0.07 |
1980 | 38 521 | 3 100 | 0 | 407 | 3 507 | 0.08 | 0 | 0.01 | 0.09 |
1981 | 39 479 | 3 500 | 0 | 328 | 3 828 | 0.09 | 0 | 0.01 | 0.1 |
1982 | 40 461 | 3 400 | 0 | 350 | 3 750 | 0.08 | 0 | 0.01 | 0.09 |
1983 | 41 468 | 3 500 | 0 | 400 | 3 900 | 0.08 | 0 | 0.01 | 0.09 |
1984 | 42 500 | 3 700 | 0 | 600 | 4 300 | 0.09 | 0 | 0.01 | 0.1 |
1985 | 43 557 | 3 500 | 0 | 500 | 4 000 | 0.08 | 0 | 0.01 | 0.09 |
1986 | 44 791 | 3 500 | 0 | 600 | 4 100 | 0.08 | 0 | 0.01 | 0.09 |
1987 | 46 060 | 3 500 | 0 | 500 | 4 000 | 0.08 | 0 | 0.01 | 0.09 |
1 Source: FAO
2 Source: FAO Fisheries Department FISHDAB
1979–87 data includes estimates of catches from small lakes which the Fish Marketing Corporation does not collect and catches in other lakes where fishermen sell directly to local villages or use for their own consumption. Marine catches from the Red Sea include estimates of quantities directly exported (illegally) to nearby countries.
3 No aquaculture in Ethiopia (Vincke, 1989, pers.comm.).
3.2 Inland catch range and potential yield
Table 4.
Water body | Period | Annual catch range (t) | Potential annual yield (t) |
Lake Abaya | 1981 | 128 | 1 000 b |
7 000 i, j | |||
14 300 c | |||
1 200 h | |||
Lake Awasa | - | 100 | 1 000 j, i |
1 500 c | |||
Lake Chamo | 3 300 b | ||
8 300 c | |||
3 500 j | |||
Lake Langano | - | 1 000 | 1 500 e, i |
3 100 c | |||
Lake Tana | - | 20 | 20 000 i |
22 600 c | |||
Lake Ziway | 1979–83 | 750–1 330 | 2 000 h |
3 000 k, j | |||
Koka Reservoir | 1964 | 100 | 2 000 b, d |
2 500 c | |||
Total Lakes/Reservoirs | 16 300 b | ||
23 300 f | |||
23 000–30 000 g | |||
60 000 c | |||
Total Rivers | 5 000–10 000 g | ||
No information available for: | |||
Lakes Abbe, Abijata, Afrera Ye'Ch'ew, Babigata, Chew Bahir, Haik, Hora, Shala, Turkana; | |||
Rivers Awash, Blue Nile, Ganale Dorya, Shabale, Sobat; | |||
Reservoirs Fincha and Zula. |
Sources:
a Balarin, 1986
b Khan, 1983
c Welcomme, 1979
d Feyissa, 1983
e IDET-CEGOS, 1979
f Giudicelli, 1984
g Aubray, 1975
h EEC project, 1979–1984
i FAO/UNDP, 1982
j Welcomme, 1972
k Gasse, 1987
Total annual yield: | 3 500 t/yr (FAO current estimate) |
Potential annual yield: | 21 300–70 000 t/yr (Table 4) |
28 000–40 000 t/yr (Aubray, 1975) |
4. STATE OF THE FISHERY
(adapted from Balarin, 1986 and Welcomme, 1979)
4.1 Yield
A description of the inland fishery has been adequately given by Aubray (1975), FAO/UNDP (1982) and Feyissa (1983). Available data have been summarized in Table 4, which indicates a potential annual yield of inland fish between 21 000 and 70 000 t.
The total inland catch is estimated at 3 500 t/yr, with a potential estimated by Aubray (1975) of 23 000–30 000 t/yr for lakes and up to 10 000 t/yr for rivers.
The inland fishery of commercial importance revolves around the Rift Valley System, Lake Tana and 7 000 km of rivers (Tables 1 and 2). It would appear that little has been reported of the past performance of this sector. Statistics have remained below 1 000 t/yr (Table 3). With the establishment of FPMC (Fish Production & Marketing Cooperation, Govt. Dept.) in 1978, fishery development was reactivated, in particular the production from inland waters.
The status of the fishery resource is given in Tables 3 and 4 and the range of values presented are an indication of the uncertainty of the statistics. The present activities are all in the hands of artisanal fishermen, now numbering between 2 000 and 7 000, from a once-active 25 000 fishermen population. The vessels are mostly non-operational and only a few boats are motorized. Major reconstruction and rehabilitation are necessary.
Aubray (1975) estimated that 1 000 professional fishermen were active on the main highland lakes, yielding between 800 and 1 000 t/yr. Some 2 000 subsistence operators were catching 400 t/yr. The bulk came from Lakes Ziway and Abaya, where 200 small canoes were operating, using baited hand lines for Nile perch, as well as some beach seines and gill nets, mainly for tilapia.
About eight cooperatives operate on Lake Ziway, selling around 1 334 t fish (1983) to the FPMC.
Over 93 species of fish are listed by Tedla (1973) and their distribution is indicated by total species number in Tables 1 and 2. Of these, Tilapia, Lates, Barbus, Clarias and Bagrus make up the bulk of the fishery, Tilapia accounting for nearly 80% of the catch. There have also been a number of introductions of indigenous and non-indigenous species throughout the major waterways of Ethiopia.
4.2 Factors influencing yield
Apart from physico-chemical limitation of productivity in the salt lakes, most water bodies appear to have considerable potential for increased yield. At present this is not realized mainly because of local food customs (there is no fish-eating tradition in Ethiopia) and the consequent lack of interest in fishing within the country, but this situation may be changing.
There appears to be a widespread need for improved stocking of selected fish species (see Section 2.5). Some water bodies have, probably for historical-zoogeographical reasons, depauperate ichthyofaunas, and the filling of vacant ecological niches could be expected to increase fishery yields substantially. Some lakes with relatively high salination could probably benefit from the introduction of salt-tolerant or brackishwater species.
No research has been carried out to evaluate the true potential of the inland lakes.
4.3 Future development possibilities
The main inland fisheries are within easy reach of the major urban centres and it is almost inevitable that, with a present catch of about (and probably even below) 10% of the estimated potential, the inland fisheries of Ethiopia will develop considerably over the next few decades. The sector has already grown considerably due to the setting up of a marketing service within the government (FPMC).
Together with an updated and comprehensive reassessment of the actual potential yields of the water bodies, including their stocking/restocking capacity, there is an urgent need for the development of an effective statistics collection network.
5. KEY BIBLIOGRAPHY
Balarin, 1986
Gasse, 1987
6. WATER BODIES DIRECTORY
Lakes | ||
Abaya (Margherita) | Babigata | Langano |
Abbe (= Abhe Bid Hayk) | Chamo (= Ruspoli) | Shala |
Abijata | Chew Bahir (= Stefanie) | Tana |
Afrera Ye‘Ch’Ew | Haik | Turkana (Rudolf) |
Asale | Hora | Ziway (Zwai) |
Awasa | ||
Rivers | ||
Awash | Ganale Dorya/Juba | Sobat |
Blue Nile | Shabale/Scebeli | |
Reservoirs | ||
Abarda | Koka | Zula |
Fincha | Legadadi |
LAKE ABAYA (MARGHERITA)
Geographical data (Welcomme, 1972, except otherwise specified) | |||
Location: | Ethiopia - 6° 2'–6° 35'N; 37° 40'–38°5'E | ||
Altitude: | 1 285 m | ||
Surface area: | 1 161 km2 | ||
Depth: | 13.1 m (max); 7.1 m (mean) | ||
Volume: | 7.924 109m3 (FAO/UNDP, 1982) | ||
Max. length: | 70 km; 60 km (FAO/UNDP, 1982) | ||
Max. width: | 29 km; 20 km (FAO/UNDP, 1982) | ||
Shoreline: | 225 km | ||
Catchment area: | 17 300 km2 | ||
Major inflowing river: Bilate | |||
Physical and chemical data | |||
Surface temperature: | 22–28° C | ||
Conductivity: | K20 670–766 μ S/cm (Loffredo & Maldura, 1941) | ||
Dissolved solids: | 516.5 mg/l (Loffredo & Maldura, 1941) | ||
Ionic composition: | mg/l* | mg/l** | |
Na | - | 206.0 | |
K | 14.1 | 16.0 | |
Ca | 15.9 | 12.1 | |
Mg | 6.3 | 5.7 | |
Cl | 52.0 | 53.0 | |
SO4 | 24.6 | 28.0 | |
SiO2 | 35.5 | 45.0 | |
HCO3+CO3 | - | 8.5 meq/l | |
Total P | - | 290 μg/l | |
Total N | - | 650.0 μg/l |
* Loffredo & Maldura, 1941
** Talling & Talling, 1965
Fisheries data | |
No. of fish species: | 25 |
Major fish species: | Bagrus, Barbus, Clarias, Cyprinus, Labeo, Lates, Tilapia (FAO/UNDP, 1982) |
Oreochromis (Gasse, 1987) | |
No. of fishermen: | 250 (Aubray, 1975) |
No. of boats: | 100 (Aubray, 1975) |
Total annual catch: | 128 t (1981) |
Potential annual yield: | |
1 000 t/yr (Khan, 1983) | |
1 200 t/yr (EEC project, 1979–84) | |
7 000 t/yr, (60 kg/ha) (Welcomme, 1972; FAO/UNDP, 1982; Gasse, 1987) | |
14 300 t/yr (123.6 kg/ha) based on MEI (Welcomme, 1979) |
LAKE ABBE (= ABHE BID HAYK)
(International water)
Geographical data (Gasse, 1987) | ||
Location: | Djibouti, Ethiopia - 11° 10'N; 41° 46'E | |
Altitude: | 235 m asl | |
Surface area: | about 250 km2; surface area decreased from 400 km2 to about 250 km2 between 1954 and 1984 (water pumped for irrigation) | |
Catchment basin: | 76 000 km2 (= Awash river basin) | |
Max. length: | 45 km | |
Max. width: | 45 km | |
Depth: | less than 12 m (mean); 36 m (max.) | |
Volume: | about 4 200 × 106 m3 | |
Major inflowing river: | Awash River | |
Outflow: | none; internal basin. | |
Physical and chemical data (cited in Gasse, 1987) | ||
pH: | 9.8–11 | |
Ionic composition: | mg/l | |
Na | 55 000 | |
K | 840 | |
Ca | 5 | |
Mg | 1.4 | |
Cl | 40 835 | |
SO4 | 17 000 | |
HCO3+CO3 | 1 060 meq/l | |
Fisheries data: | no fishing activity. |
LAKE ABIJATA (ABIYATA)
Geographical data (Welcomme, 1972) | |||
Location: | Ethiopia - 7° 36'N; 38° 48'E | ||
Altitude: | 1 573 m | ||
Surface area: | 205 km2 | ||
Depth: | 14.2 m (max); 7.6 m (mean) | ||
Volume: | 1.6 km3 | ||
Max. length: | 20.9 km | ||
Max. width: | 12.4 km | ||
Shoreline: | 61.9 km | ||
Catchment area: | 1 630 km2 | ||
Special features: | The lake forms a water bird reserve; there is no fishing. | ||
Physical and chemical data | |||
Surface temperature: 23–26° C | |||
Conductivity: | K20 10 700 μS/cm | ||
K20 30 000 μS/cm (Loffredo & Maldura, 1941) | |||
Dissolved solids: | 8 358 mg/l (Loffredo & Maldura, 1941) | ||
Ionic composition: | mg/l* | mg/l** | |
Na | 3 000 | 6 375 | |
K | 75.3 | 331 | |
Ca | 8.5 | <3 | |
Mg | 6.0 | <7.5 | |
Cl | 1 500 | 3 240 | |
SO4 | 67.4 | 210 | |
HCO3+CO3 | - | 210 meq/l | |
Total P | - | 890 μg/l |
* Loffredo & Maldura, 1941
** Talling & Talling, 1965
Fisheries data
Major fish species: tilapia
There is no fishing.
LAKE AFRERA YE'CH'EW
Geographical data | |
Location: | Ethiopia - 13°15'N; 40° 55'E |
Altitude: | 103 m bsl |
Surface area: | 140 km2 |
Max. length: | 25 km |
Max. width: | 8 km |
Max. depth: | 160 m |
Special feature: | isolated, highly saline. |
LAKE ASALE
Geographical data | |
Location: | Ethiopia - 14°N; 40° 20'E |
Altitude: | about 100 m bsl |
Special feature: | highly saline, potash mining |
LAKE AWASA
Geographical data (Welcomme, 1972) | |||
Location: | Ethiopia - 7° 03'N; 38° 24'E | ||
Altitude: | 1 708 m | ||
Surface area: | 130 km2; the lake forms a swamp of about 72 km2 to the east | ||
Depth: | 21.6 m (max); 10.7 m (mean) | ||
Volume: | 1.3 km3 | ||
Max. length: | 17 km | ||
Max. width: | 11 km | ||
Shoreline: | 52 km | ||
Catchment area: | 1 250 km2 | ||
Physical and chemical data (Welcomme, 1972) | |||
Surface temperature: 23–26° C | |||
Conductivity: | K20 790–860 μ S/cm (Loffredo & Maldura, 1941) | ||
K20 1 050 μ S/cm (Talling & Talling, 1965) | |||
Dissolved solids: | 650.4 mg/l | ||
Ionic composition: | (Talling & Talling, 1965) | ||
mg/l | |||
Na | 235 | ||
K | 45 | ||
Ca | 4.4 | ||
Mg | 4.7 | ||
Cl | 34 | ||
SO4 | <2 | ||
SiO2 | 72 | ||
HCO3+CO3 | 10.5 meq/l | ||
Total P | 98 μg/l | ||
Fisheries data | |||
No. of fish species: | 3: Barbus, Clarias, Tilapia (FAO/UNDP, 1982) | ||
No. of fishermen: | 38 (Feyissa, 1983) | ||
80 (Aubray, 1975) | |||
No. of boats: | 19 (Feyissa, 1983) | ||
Total annual catch: | 100 t (current) | ||
Potential annual yield: | |||
1 000 t/yr (77.5 kg/ha/yr) (Welcomme, 1972; FAO/UNDP, 1982) | |||
1 500 t/yr (114 kg/ha/yr) based on MEI (Welcomme, 1979) |
LAKE BABIGATA
Geographical data | |
Location: | Ethiopia |
Altitude: | 1 600 m |
Surface area: | 0.7 km2 |
Depth: | 60 m (max) |
Volume: | 0.2 km3 |
Shoreline: | 2 km |
Physical and chemical data | |
pH: | 9.3 |
LAKE CHAMO (RUSPOLI)
Geographical data (Welcomme, 1972, 1979) | |
Location: | Ethiopia - 5° 40'N; 37° 37'E |
Altitude: | 1 282 m |
Surface area: | 551 km2 |
Depth: | 12.7 m (max.); 6 m (mean) |
Volume: | 4.1 109m3 |
Max. length: | 36 km |
Max. width: | 23 km |
Shoreline: | 118 km |
Major inflowing river: | overflow from Lake Abaya through Uafo River; there is no outflow. (Gasse, 1987) |
Physical and chemical data (Welcomme, 1972) | |
Surface temperature: | 25–28° C |
Conductivity: | K20 927 μ S/cm (Loffredo & Maldura, 1941) |
Dissolved solids: | 651.2 mg/l |
Fisheries data | |
Main fish species: | |
Bagrus docmac, Lates niloticus, Barbus sp., Clarias sp., Labeo sp. (Gasse, 1987; FAO/UNDP, 1982) | |
Potential annual yield: | |
3 300 kg/yr (60 kg/ha/yr (FAO/UNDP, 1982; Kahn, 1983) | |
3 500 kg/yr (Welcomme, 1972) | |
8 300 kg/yr (150 kg/ha/yr) based on MEI (Welcomme, 1979) |
LAKE CHEW BAHIR (STEFANIE)
Geographical data | |
Location: | Ethiopia - 4° 40'N; 36° 50'E |
Surface area: | 0 – 50 km2 |
Major inflowing river: | Galana Sagan |
Outflowing river: | none - internal basin |
Special features: | swampy, non-permanent lake. |
LAKE HAIK
Geographical data | ||
(miscellaneous sources, cited in Balarin, 1986) | ||
Location: | Ethiopia - 10° 15'N; 39° 57'E | |
Altitude: | 1 670–2 030 m | |
Surface area: | 23–35 km2 | |
Depth: | 88 m (max.); 37.4 m (mean) | |
Total length: | 7 km | |
Max. width: | 5 km | |
Volume: | 0.9 km3 | |
Shoreline: | 22 km | |
Physical and chemical data (after FAO/UNDP, 1982) | ||
pH: | 9 | |
Conductivity: | 800 μs/cm | |
Ionic composition: | mg/l | |
Na | 90 | |
K | 16 | |
Ca | 24 | |
Mg | 56 | |
Cl | 4.4 | |
SO4 | 9 | |
SiO2 | 2 | |
HCO3+CO3 | 8.9 meq/l | |
Fisheries data | ||
Main fish species: | Clarias sp., tilapia. |
LAKE HORA (HORO)
Geographical data (miscellaneous sources, cited in Balarin, 1986) | ||
Location: | Ethiopia - 8° 50'N; 39° 0'E | |
Altitude: | 1 600–1 850 m | |
Surface area: | 1 km2 | |
Depth: | 35 m (max.); 17.5 (mean) | |
Volume: | 0.2 km3 | |
Shoreline: | 3.3 km | |
Physical and chemical data (after FAO/UNDP, 1982) | ||
pH: | 9.2 | |
Ionic composition: | mg/l | |
Na | 500 | |
K | 51 | |
Ca | 6–8 | |
Mg | 47 | |
Cl | 201 | |
SO4 | 19 | |
SiO2 | 55 | |
HCO3+CO3 | 26.89 meq/l | |
Fisheries data (after FAO/UNDP, 1982) | ||
Main fish species: | Clarias sp., tilapia |
LAKE LANGANO
Geographical data (Welcomme, 1972) | |||
Location: | Ethiopia - 7° 36'N; 38° 45'E | ||
Altitude: | 1 585 m | ||
Surface area: | 230 km2 | ||
Depth: | 46.2 m (max.); 17 m (mean) | ||
Volume: | 3.8 km3 | ||
Max. length: | 23.2 km | ||
Max. width: | 16 km | ||
Shoreline: | 77.5 km | ||
Catchment area: | 1 600 km2 | ||
Physical and chemical data | |||
Surface temperature: 22–26° C | |||
Conductivity: | K20 1 900 μ S/cm (Talling & Talling, 1965) | ||
K20 2 200 μ S/cm (Loffredo & Maldura, 1941) | |||
Dissolved solids: 1 644 mg/l (Loffredo & Maldura, 1941) | |||
Ionic composition: (Loffredo & Maldura, 1941) | |||
mg/l | |||
Na | 500 | ||
K | 27.5 | ||
Ca | 2.5 | ||
Mg | 2.7 | ||
Cl | 216 | ||
SO4 | 28 | ||
SiO2 | 54 | ||
HCO3+CO3 | 15.0 meq/l | ||
Total P | 165 μg/l | ||
Fisheries data | |||
Main fish species: | Barbus sp., Clarias sp., Oreochromis niloticus (FAO/UNDP, 1982; Gasse, 1987) | ||
No. of fishermen: | 44 (Feyissa, 1983) | ||
Total annual catch: | 1 000 t | ||
Potential annual yield: | |||
1 500 t/yr (65 kg/ha/yr) (IDET-CEGOS, 1979, FAO/UNDP, 1982) | |||
3 100 t/yr (136 kg/ha/yr) based on MEI (Welcomme, 1979) |
LAKE SHALA
Geographical data (Welcomme, 1972) | |||
Location: | Ethiopia - 7° 30'N; 38° 30'E | ||
Altitude: | 1 567 m | ||
Surface area: | 409 km2 | ||
Depth: | 266 m (max.); 86 m (mean) | ||
Volume: | 37 km3 | ||
Max. length: | 27 km | ||
Max. width: | 17 km | ||
Shoreline: | 110 km | ||
Catchment area: | 3 920 km2 | ||
Major inflowing river: | Gida River; there is no outflow (Gasse, 1987) | ||
Special feature: | crater lake | ||
Physical and chemical data | |||
Conductivity: | K20 20 400 μ S/cm (Loffredo & Maldura, 1941) | ||
Dissolved solids: | 16 771 mg/l (Loffredo & Maldura, 1941) | ||
Ionic composition: | mg/l* | mg/l** | |
Na | 5 894 | 6 250 | |
K | 440 | 252 | |
Ca | 10 | <3 | |
Mg | 8.8 | <7.5 | |
Cl | 3 136 | 3 300 | |
SiO2 | - | 130 | |
SO4 | 128.7 | 275 | |
HCO3+CO3 | - | 200 meq/l | |
Total P | - | 900 μg/l |
* Loffredo & Maldura, 1941
** Talling & Talling, 1965
Fisheries data
Low production, unfished (Gasse, 1987).
No. of fish species: 1: Oreochromis niloticus (cited in Gasse, 1987).
LAKE TANA
Geographical data (Welcomme, 1972) | |||
Location: | Ethiopia - 12°N; 37° 20'E (approximate centre of lake) | ||
Altitude: | 1 829 m | ||
Surface area: | 3 500 km2 | ||
Catchment area: | 16 500 km2 (Gasse, 1987) | ||
Depth: | 14 m (max.); 8 m (mean) | ||
Volume: | 28 km3 | ||
Max. length: | 80 km | ||
Max. width: | 64 km | ||
Major inflowing rivers: 60 affluents; the largest are the Little Abbai, Reb and Gumura Rivers | |||
Outflowing river: | Blue Nile | ||
Physical and chemical data | |||
pH: | 7.5–8.2 (Bini, 1940) | ||
Dissolved solids: | 151 mg/l (Bini, 1940) | ||
174 mg/l (Grabham & Black, 1925) | |||
Ionic composition: | mg/l* | mg/l** | |
Ca | 27.1 | 18.7 | |
Mg | 10.0 | 9.3 | |
Cl | 8.0 | 8.0 | |
SiO2 | - | 22.0 | |
HCO3+CO3 | - | 1.7 meq/l |
* Grabham & Black, 1925
** Bini, 1940
Fisheries data | ||
No. of fish species: 20 (Boulenger, 1907) | ||
Cyprinidae: | Varicorhinus beso | |
Discognathus quadrimaculatus | ||
Barbus (14 sp.) | ||
Clariidae: | Clarias tsanensis (endemic of L. Tana) | |
C. mossambicus | ||
C. anguillaris | ||
Cichlidae: | Oreochromis niloticus (Gasse, 1987) | |
Main catches: | Clarias spp. + Barbus spp. = 90% of the catches (Gasse, 1987) | |
No. of fishermen: | 60 (Aubray, 1975) | |
500 (cited in Balarin, 1986) | ||
No. of boats: | 10 (Aubray, 1975) | |
Total annual catch: | 20 t (cited in Balarin, 1986) | |
Potential annual yield: | ||
20 000 t/yr (55 kg/ha/yr) (FAO/UNDP, 1982) | ||
22 600 t/yr (65 kg/ha/yr), based on MEI (Welcomme, 1979) |
Fig. 3. LAKE TURKANA - RUDOLF
(Welcomme, 1972)