This dataset consists of phyto- and zooplankton counts, chlorophyll concentration and fish catch data from the Cumbrian Lakes (Blelham Tarn, Esthwaite Water, Windermere north and south basins). The data span the years 1940 to 2013 but time series vary in length among different species and sites, and fish data are only available from Windermere. The original data were initially collected by the Freshwater Biological Association (FBA) but have been collected by CEH and its predecessor Institute of Freshwater Ecology (IFE) since 1989.