1.1 Programme and objectives
1.2 General geographical description
By agreement between the Government of the United Republic of Tanzania and the Norwegian Agency for International Development (NORAD), the fishery research vessel “Dr. Fridtjof Nansen” carried out three surveys of the fishery resources in Tanzanian waters in 1982-1983.
During these surveys the fish resources living in the depth region 10-500 m were investigated. The hydrographical situation during the different surveys were studied. The programme was carried out by a joint team of Norwegian and Tanzanian scientists. The timing and the scientific staff of the different surveys are shown in Table 1.1. After each survey a cruise report was presented (Anon, 1982a, 1982b, 1983). Later in this report the surveys are referred to as number one, two and three.
Table 1.1 Timing and scientific staff of the three surveys with R/V “Dr. Fridtjof Nansen” in Tanzanian waters.
|
Survey No. |
1 |
2 |
3 |
|
Time |
16 June - 8 July 1952 |
12 November-3 December 1982 |
11 - 26 May 1983 |
|
Staff |
S. Myklevoll, Norwayx) |
S. Myklevoll, Norway |
S. Myklevoll, Norway |
|
H. Kismul, Norway |
H. Kismul, Norway |
K. Hansen, Norway |
|
|
K. Lauvås, Norway |
S. A. Iversen, Norway x) |
R. Sætre, Norway x) |
|
|
B. Bakken, Norway |
B. Bakken, Norway |
B. Bakken, Norway |
|
|
T. Mørk, Norway |
E. Øvretveit, Norway |
H. Abrahamsen, Norway |
|
|
M. M. Hassan, Tanzania |
G. B. Schmidt, FAO |
G. D. Msumi, Tanzania |
|
|
M. A. K. Ngoile, Tanzania |
M. A. K. Ngoile, Tanzania |
S. P. N. Kimaro, Tanzania |
|
|
J. Yonazi, Tanzania |
J. Yonazi, Tanzania |
E. F. B. Katunzi, Tanzania |
|
|
H. B. Pratap, Tanzania |
P. K. Chisara, Tanzania |
H. B. Pratap, Tanzania |
|
|
K. M. Lwiza, Tanzania |
W. V. Haule, Tanzania |
|
|
|
B. A. S. Mwamoto, Tanzania |
O. S. Faki, Tanzania |
|
x) Cruise leader
The coastline of Tanzania extends from the northern boundary with Kenya, latitude 4°38'S to the southern boundary with Mozambique, latitude 10°30'S (Fig. 2.1). The coastline has a total length of approximately 800 km. There are many small and medium sized islands, most of which are fringed by coral reefs. The biggest are Zanzibar, Pemba and Mafia, in that order.
The two typical seasons are the southwest monsoon which lasts from April to October/November and the northeast monsoon from November to March (Newell, 1957). The northeast monsoon period is climatically characterized by higher air temperatures, lower wind speeds and consequently calmer sea. During the southwest monsoon the air temperature is lower, the wind stronger and the sea is rougher. The short rains occur intermittently between September and December, (Bwathondi, 1980). The coast receives the heavy rains between March and May.
The major rivers of Tanzania (Fig. 2.1) are: Pangani, Wami, Ruvu, Rufiji, Mbwemkuru and Ruvuma. The peak outflow from these rivers occurs in March-May. However, the influence of the freshwater outflow from the rivers is restricted to the inshore waters, most probably due to the prevailing wind and current conditions. Fig. 3.6.1 shows that all patches of low salinity are moved slightly northwards, even for a big river like the Rufiji. The rivers carry a lot of silt which builds up deltas e.g. the Rufiji delta which covers about 400 km2. Mangrove trees thrive at the river mouths. The trees are important for productivity of the inshore waters.
The Rufiji mangrove forest is the largest single stand on the eastern shores of Africa. The Rufiji delta is today the most important source of prawns in Tanzania, producing over 80% of the total prawn catch, (Mwaiseje, 1982).
The continental shelf is generally narrow. The minimum width to the 200 m depth contour is less than 2 km at latitude 9°30'S. The maximum width is approximately 80 km at latitude 6°25'S, this includes the Zanzibar island. Unlike Zanzibar, Pemba island does not form part of the shelf. It is separated from both the Mainland and Zanzibar by a deep channel.
