East African Fisheries Research Organization Annual Report 1951

The examination of a considerable amount of data has led to the conclusion that Lake Victoria should be considered as many lakes within a lake. This is not a vague and seemingly obvious remark based on the superficial observation that it is a very large lake containing numerous islands and with a highly indented coastline, and therefore providing variable local conditions. Such local conditions would exist in any lake whose basin departed from a simple geometric form. But evidence has now been collected to show that really significant differences occur between different regions within the lake. These differences are apparent from a variety of data, including the nature of the bottom deposits, the chemical and hydrological condition of the water, the amount and kind of plankton and the distribution and abundance of the fauna. Our findings are as yet somewhat sketchy, and it will be a long time before it will be possible to draw an adequate picture of the various regions of the lake; it is however, of great value to have reached a position enabling us to form this general concept. The most striking and definite evidence is derived, as might be expected, from hydrological data. Details of this work are contained in the hydrological section of this report. Any data recorded below should be considered as applying only to the particular areas mentioned. In other words it would, to draw an obvious example be wrong to suppose that because fish grow at a particular rate in one part of the lake they will grow at the same rate or to the same size in other regions of the lake.