COUNTRY FILES (Contd.)

TANZANIA

1. GEOGRAPHY AND CLIMATE (Welcomme, 1979a)

The topography of continental Tanzania (surface area of 886 040 km²) (Fig. 1) is highly varied but four main types of terrain predominate:

1. the coast, below 300 m altitude:
2. the alluvial plains of the main eastward flowing rivers, from 300 to 1 000 m in altitude;
3. an inland plateau which covers most of the country, 1–2 000 m; and
4. highlands to the south and northeast, which range between 2 000 and 5 900 m. Parts of both eastern and western arms of the Rift Valley systems lie within Tanzania.

The climate is linked to the topography, having also four main areas:

1. a hot humid coastal zone;
2. a hot arid central area;
3. high moist lake regions; and
4. temperate uplands.

The overall climate is regulated by the monsoons which give two equinoctial rains, one from March to June, the other from October to December. At other times of the year the weather is hot and dry. Tanzania is a predominantly agricultural country, although some areas are used mainly for cattle ranching and game parks.

2. HYDROGRAPHY (Welcomme, 1979a; Balarin, 1985b)

2.1 Lakes (See Fig. 2)

Tanzania is extremely well endowed with lakes. The total water area in Tanzania covers nearly 61 500 km² or about 6.5% of the total land area, 88% of which is made up by three major lakes. The main lakes are shared with neighbouring countries and are generally associated with the Great Rift Valley. These include Lake Tanganyika and Lake Nyasa, both elongated and rather deep, and Lake Victoria, which is a broad and relatively shallow lake.

Almost half the areas of two of the Great Lakes (Victoria and Tanganyika) lie within Tanzania, while Tanzania possesses 800 km of shoreline on the third (Lake Malawi/Nyasa). Other large lakes include Lake Rukwa and Kitangiri and a group of Rift Valley soda lakes (Lakes Natron, Eyasi and Manyara) which are very shallow and liable to dry up in low rainfall periods.

Numerous smaller lakes are scattered throughout the country.

2.2 Rivers, Floodplains and Swamps (see Fig. 2)

There are comparatively few river systems within Tanzania as the main central plateau is arid. Four distinct river basins are apparent. The greater part of the eastern and southern regions are drained by rivers flowing to the Indian Ocean. These include one of the largest rivers in Africa, the Rufiji, with an average dis-charge of 1 133 m³/sec, and minor rivers such as Pangani, Ruwami, Ruvu and the Lake Nyasa rivers. The remaining basins are associated with either Lake Victoria, Lake Tanganyika or the interior drainage including the Lake Rukwa Basin.

Fig. 1. LOCATION MAP AND ADMINISTRATIVE DIVISIONS OF TANZANIA
(Balarin, 1985b)

DRAINAGE BASIN

1. Indian Ocean
2. Atlantic Ocean (Lake Tanganyika)
3. Mediterranean Sea (Lake Victoria)
4. Interior drainage

NAME OF LAKE OR RESERVOIR (construction date)

1. Lake Eyasi
2. Lake Rukwa
3. Lake Tanganyika
4. Lake Victoria
5. Lake Natron
6. Lake Manyara
7. Lake Nyasa
8. Nyumba ya Mundu Dam (1945)
9. Kidatu Reservoir (1974)
10. Mtera Reservoir (1979)
11. Hombolo Reservoir
12. Lake Ikimba
13. Lake Jipe
14. Lake Chala
15. Lake Kitangiri
16. Lake Balangida
17. Kibasira Swamp
18. Malagarasi Swamp
19. Bahi Swamp
20. Rufiji Floodplain

Fig. 2. HYDROLOGICAL ZONES AND MAIN LAKES IN TANZANIA
(S.M.D., 1976)

Fig. 3. THE DISTRIBUTION OF RESERVOIRS IN TANZANIA
(Bailey, 1966)

The Pangani River (360 km) drains the northern highlands and the 720 km Rufiji system drains the southern uplands. The Ruvuma River forms the border with Mozambique for 640 km. The other major river system, the Malagarasi, flows from the central plateau into Lake Tanganyika. The main channel is some 560 km long and expands into the Malagarasi Swamps. The Rufiji basin contains three important floodplains (Kilombero, Usanga and Rufiji). Important swamps include Malagarasi, Bahi and Kilosa.

Table 1. DISTRIBUTION OF RESERVOIRS IN TANZANIA
(Balarin, 1985)

Flow patterns vary with rainfall and rivers generally flow for 5–6 months of the year only, during the wet season. This condition is variable according to rainfall intensity; high altitude mountainous areas are more likely to have an all-year-round stream flow pattern.

2.3 Reservoirs (see Figs. 2, 3 and Table 1)

Water conservation dams have been constructed for domestic, livestock, irrigation or factory use, as well as flood control; in all cases these have been stocked with fish. Some of the earlier dam constructions are reviewed by Bailey (1966) and are summarized in Table 7 and Figure 9 according to the following categories:

In all, Bailey (1966) describes 490 dams, nearly 51% of which are less than 0.5 ha. Most of them are non-perennial, especially in the more arid regions. Most dams were built in the drier regions, in particular the eastern rift, the Masai Steppe and the western and central plateaus.

The Nyumba ya Mungu Reservoir was constructed on the Pangani River in 1965. A further reservoir, which will be larger than Nyumba ya Mungu, is planned at Stiegler's Gorge on the Rufiji River. There are two reservoirs (Mtera and Kidatu) on the Great Ruaha, a tributary of the Rufiji. Hombolo is a smaller impoundment on the Wami. There are also numerous small reservoirs which have been stocked with fish.

2.4 Coastal Lagoons: There are none of significant size.

3. FISHERY PRODUCTION/POTENTIAL

3.1 Aquaculture

Some 10 000 ponds with a surface of 1 000 ha had been constructed by 1963, but because of poor technology and management many of these have since fallen into disuse.

In 1974, it was estimated that aquaculture production was about 1 800 t/yr with a forecasted rise to 80 000 t/yr by 1985 and 145 000 t/yr by 1995. In a more recent appraisal of the situation, FAO (1983b) considers that only about 800 ponds/reservoirs are still operational, yielding a low 130 kg/ha/yr. Several ponds are poorly managed, too shallow, lack proper water inlet/outlet, are overgrown or generally abandoned.

UNDP (1981) suggests that the fish yield of the 600–1 000 ponds believed functional in 1980 was no more than 8–13 t (i.e. 0.1 ha mean size at 130 kg/ha/yr). The latter is perhaps the most realistic estimate of total yield.

A good potential exists in Tanzania for the development of aquaculture in the large number of ponds already constructed, in several hundreds of water storage reservoirs, and in the development of the coastal belt through brackishwater aqua- culture. The stocking of small reservoirs, although initiated in various regions, still has not gained much momentum or any significant dimensions.

3.2 Fish production and per caput supply

Table 2. FISH PRODUCTION AND PER CAPUT SUPPLY - Tanzania, 1970–1987

¹ Source: FAO
² Source: FAO Fisheries Statistics (see note below) (see also section 3.3)
Note: Recent report on Tanzania catch reporting system indicates need to revise raising factors. Total catch probably overestimated. (FAO Yearbook 1986 vol. 62)
³ included in “Inland capture” if not specified
⁴ - = data not available
⁵ Vincke, 1989, pers. comm.

3.3 Inland catch range and potential yield

Table 3.

Footnotes to Table 3 * See main text for information sources used.
(a) Combination of official and other estimates, as quoted in Reynolds, 1989.
(b) Mtera also includes Ruaha River and other waters in Dodoma Region.
(c) Covers Mbeya Region section of Ruaha River.
(d) Includes also those sections of Ruaha, Wami, Ngerengere, Luhombero, Mkata, and Manyera Rivers flowing within or through Morogoro Region.
(e) Kagera Lakes Complex.
(f) Balarin (1985b), including the numerous swamps and minor lakes whose potential annual yield is not detailed in Table 3.

No data available for:
Lakes Ambussel, Bisongo/Ngoma (e), Burungi, Chala, Igalula, Ilamba, Jipe, Kajumbura (e), Kingili, Kitere, Magadi, Mamka, Mansi, Minyere, Mkoe, Ndutu, Nziwi, Rushwa, Sagara, Sekena (e), Welu;
Rivers Pangani, Ruvu, Songwe;
Reservoirs Eluanata, Geita, Igombe, Kalimawe, Kidatu, Manda, Mindutulieni, Muchlur, Mwetemo, Rwamkona.

Total annual yield: 211 975–221 975 t (combination of official and other estimates, as quoted in Reynolds, 1989)

Potential annual yield: 226 500–358 500 t

4. STATE OF THE FISHERY

4.1 Yield

Freshwater fish account for over 85% of total landings. The more common species include Lates, Limnothrissa, Stolothrissa (or dagaa), tilapia, Clarias, Haplochromis, Bagrus and Labeo. Estimated yield potential ranges between 220 000 and 360 000 tons per year (Table 3).

Tanzania has over 61 500 km² of inland waters, including numerous lakes and rivers, of which Lakes Victoria, Tanganyika and Nyasa provide the majority of the catch.

The yield from Lake Victoria has increased from 46 000 t/yr in 1975 to 99 000 t/yr in 1985, with a corresponding increase in catch per unit of effort. Haplochromis made up 35% of the catch in 1975 but reduced to 12% in 1985, while Nile perch has been increasing in importance (0% in 1975; 38% in 1985). However, it is anticipated that the Nile Perch population will begin to decrease as the Haplochromis stocks become depleted. Potential MSY has been estimated at 63 000–100 000 t/yr (Table 3) but FAO (1984) suggested that the lower value was a more realistic figure.

Lake Tanganyika fish yield estimates for 1983–86 fluctuated between 100 000 t/yr (official estimate) and 250 000 t/yr (FAO estimate). In 1975, the official estimate was 64 000 t/yr. FAO (1984) suggested a 100 000 t/yr potential.

Lake Nyasa, of which about 300 km of shoreline border Tanzania, yielded 25 000 to 35 000 t/yr (official estimate) or 10 000–15 000 t/yr (other estimates) in 1986. The potential is not well defined and ranges from 15 000 to 100 000 t/yr (Table 3).

Other waters of significant fishery potential include Nyumba ya Mungu which, in 1970, recorded a 25 000 t/yr catch; its potential, however, is likely to be only 4 000–5 000 t/yr, which is closer to the most recent recorded yield: 4 300 t in 1987. Lake Rukwa yielded 6 000 t/yr in 1986 (official estimate), against a recommended potential yield of 3 000 t/yr (FAO, 1984). Numerous swamps and minor lakes and up to a potential of 40 000–50 000 t/yr.

4.2 Factors influencing yield

Whereas the fisheries mentioned above depend much on the development of a suitable infrastructure of commercial-scale fisheries, several other fisheries, particularly Lakes Rukwa and Kitangiri, are subject to large natural fluctuations in area. The case of the Nyumba ya Mungu Reservoir shows a production rise and subsequent fall which conform to the normal pattern for newly established reservoirs. The peak production of 28 500 t seems excessive for a body of water of this size, but the present yield is consistent with yield patterns for other reservoirs in Africa.

4.3 Future development possibilities

There is the possibility for catch increases from numerous inland water bodies of Tanzania. Apart from Lake Victoria (which seems to be in an unbalanced condition), Lake Tanganyika could theoretically sustain a much higher yield. For the third Great Lake (Lake Nyasa) it is not clear whether or not the present catch range is close to the maximum sustainable yield. Additional production may be anticipated from the Mtera Reservoir on the Great Ruaha River and from the numerous smaller reservoirs that have been stocked.

Further development of fish production is hoped for by the spread of aquaculture, where it is estimated that 2 000 t could be produced from existing ponds, and 10 000 t from expanding aquaculture in about 40 000 ha of small dams and reservoirs. Increases in production through aquaculture could obviously surpass this.

From the wide range of potential estimates proposed for Tanzanian inland waters fisheries, the actual knowledge of the resources appears to be very limited; further studies are necessary.

5. KEY BIBLIOGRAPHY

Balarin, 1985b

6. WATER BODIES DIRECTORY

LAKE AMBOSELI
(International water)

LAKE AMBUSSEL

LAKE BABATI

Fisheries data
Total annual catch and effort:

LAKE BALANGIDA

LAKE BALANGIDA LELU

LAKE BASUTO

Fisheries data
Total annual catch and effort:

LAKE BISONGO (= NGOMA)

LAKE BURIGI

LAKE BURUNGI

LAKE CHALA
(International water)

LAKE EMPAKAI

LAKE EYASI

LAKE GOMBO

LAKE HAUBI

Fisheries data
Total annual catch and effort:

LAKE IGALULA

LAKE IKIMBA

LAKE ILAMBA

LAKE JIPE
(International water)

Fisheries data (FAO/UNDP, 1966)
Total annual catch and effort: 150 t (in 1965) in Kenya waters only
Potential annual yield: 300 t total lake

LAKE KAJUMBURA

LAKE KINDAI

Fisheries data
Total annual catch and effort:

LAKE KINGILI

LAKE KITANGIRI

Fisheries data
No. of fish species: 20 (Mann, 1965)
Total annual catch and effort:

* Welcomme, 1972
** Regional Fisheries Office, 1988

Potential annual yield: 1 000 t/yr (FAO, 1984)

LAKE KITERE

LAKE LWELO

LAKE MAGADI

LAKE MAGADI

LAKE MAMKA

LAKE MANSI

LAKE MANYARA

Fisheries data
Total annual catch and effort:

LAKE MINYERE

LAKE MKOE

LAKE MUJUNJU (= RWAKAJUNJU)

Fisheries data
Total annual catch and effort:

LAKE NATRON
(International water)

Physical and chemical data (Guest & Stevens, 1951)
Ionic composition:

LAKE NDUTU

LAKE NYASA/MALAWI
(International water)

* Official estimate, Fisheries Department, 1988.
** Current estimate, several authors cited in Reynolds, 1989

Campbell and Moreni (1988) noted that fishing activity along the Tanzanian shore appeared to be minimal, owing to lack of gear and inadequate craft.

Potential annual yield: (cited in Balarin, 1985b)
                      15 000 t/yr (Robinson, 1982)
                    100 000 t/yr (MNRT, 1983)

Fig. 4. LAKES NYASA/MALAWI AND MALOMBE
(Welcomme, 1972)

LAKE NZIWI

LAKE RUKWA

Potential annual yield: 3 000 t (FAO, 1984)

LAKE RUTAMBA

LAKE SAGARA

LAKE SEKENA

LAKE SINGIDA

Fisheries data
Total annual catch and effort: