Notwithstanding the small size of the country, the natural water bodies exploited for fishery purposes are of varied types.
The water level of the Shire River and its swamps changes substantially with annual fluctuations in rainfall.
Lake Chilwa is shallow and has brackish water in its closed basin. Lake Malombe is a water body of an eutrophic type. Lake Malawi is partly of an eutrophic character (in the south), the rest being of oliotrophic character.
No scientific basis for estimating the fish production potential of the water bodies of Malawi exists at present. The potential sustained maximum production was estimated at 17,500 tons in 1956 and 1961, at between 16,000 and 20,000 tons in 1963, and at 26,000 tons in 1964. These estimates are guesses rather than findings of scientific studies.
It is difficult to plan a development programme without more accurate knowledge of the potentiality of the waters. In May 1965, therefore, the expert requested from the Fisheries Research Station of Malawi a summary note on available knowledge on the water bodies of the country, as well as on additional studies needed to establish a rational fisheries management programme.
The investigations yet to be made, the expert thought, would justify the establishment of a scheme of the size of the Kariba project organised under UNDP/SF auspices because of the magnitude of the lakes and other water bodies, as well as because of the potential importance of fisheries to the economy of the country.
One of the most important phases of the work which should be carried out in the field of fisheries research in Malawi is the study of breeding and growing conditions of tilapia species in Lake Malawi. This is of paramount importance for protecting the fish stock, since the findings would make it possible for fisheries workers to distinguish immature fish from others. The work may be carried out in ponds or, better still, in tanks where the natural habitat of the species should be reproduced as far as possible.
A study of the possibilities of introducing ndagala (Stolothrissa tanganicae) from Lake Tanganyika into Lake Malawi and, at a later stage, Lates, should also be one of the more important tasks in the field of research. If the results are favourable, fish production from the deep waters of the lake could probably be considerably increased.
