Pelagic primary production in Kainji Lake. Technical Report 3.
As part of the Kainji Lake Research Project being carried out by the Government of Nigeria with the assistance of the United Nations Development Programme and the Food and Agriculture Organization of the United Nations, the pelagic primary production in the lake was studied from December 1970 to September 1972. Production per volume of water and per unit surface area was estimated using the oxygen light and dark bottle technique. Seasonal variations in solar radiation transparency, temperature and composition of subsurface light were also measured. The average production was found to be 822 mg C/m2 /d. The transparency and the nutrient content of the water are the main factors limiting photosynthetic production. The phytoplankton production in Kainji Lake has been compared with production in other tropical waters and an attempt has been made to relate the pelagic primary production to fish production. The results indicate an order of magnitude of fish catch for Kainji Lake of 15 kg/ha/a, assuming that 20% of the total production of fish is harvestable. This estimate, while of no higher accuracy than other estimates that have been given, is the lowest so far proposed.