This dataset consists of estimated gonad weight and associated data on male pike (Esox lucius) from net sampling in Windermere, Cumbria. Data collection began in 1945. The 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. Full details about this dataset can be found at https://doi.org/10.5285/c1114f67-c307-4aab-9299-95d4fbbdd53f