Observations on the Cladocera of Lake George, Uganda

Seven species of Cladocera were recorded from the shallow, equatorial Lake George in Uganda, during the period 1967–72. Of these only three, Moina micrura Kurz, Ceriodaphnia cornuta Sars and Daphnia barbata Weltner, are found in the open water and they form a small proportion of the total zooplankton biomass, which is dominated by a cyclopoid copepod. All three species are found throughout the year and carry parthenogenetic eggs at all times. They are smaller species than those predominating in some other East African lakes and some comparisons are also made between C. cornuta and four other species of that genus studied in Great Britain. The mean body lengths and clutch sizes of ovigerous females of C. cornuta vary little through the year. This is, presumably, a reflection of the relatively constant environment in Lake George. Alona poppei is only found in the open water intermittently and is thought to be swept from the peripheral swamps during heavy rains. The general scarcity of Cladocera in Lake George is thought to be due, either to a shortage of food particles of suitably small size in the phytoplankton, which is dominated by large blue‐green algae, or to predation. Although Cladocera are certainly eaten by fish, quantitative data, with which to substantiate either of these hypotheses, is lacking.