| Summary: | The population dynamics of rotifers in Loch Leven was studied over a three year period (1977-1979) from samples collected at weekly intervals. Since up to 65 per cent of the smaller rotifers may be lost when collected with a net of 45mm mesh size, the samples were collected by volumetric methods and concentrated by sedimentation. Loch Leven was generally well-mixed with rotifers distributed more or less randomly throughout the pelagic zona on most occasions. Population densities could, therefore, be estimated from only a smal1 number of samples. Rotifers are generally difficult to identify since little is known of their ecology and their morphology is often strongly influenced by environmentally induced polymorphism. In order to avoid any major systematic misunderstanding the species list for Loch Leven is accompanied by short descriptions of the animals with notes on the problems of identification. Rotifers showed a distinct pattern of seaonal succession which appeared to be influenced, primarily, by species specific responses to changing water temperature. Many species showed a well-defined range of temperature preference beyond which their reproductive success was seriously impaired .Within this range of temperature preference, the birth rate was dependent upon water temperature and food availability. Many rotifer species appeared to be food specialists and some observations were made on their feeding habits. Attempts were made to culture rotifers on various algal species in the laboratory to test hypotheses suggested by field observtions. The predation of rotifers by Cyclopoid copepods, the predatory rotifer Asolanchna priodonta end larval perch is discussed, However, little quantitative information was available and the impact of predation on rotifer populations in Loch Leven is still unknown.
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