The reproductive potential of an organism, also known as fecundity, is determined by several factors. In fish, theory suggests that individual size would have the strongest influence on both the number of eggs and the size of eggs. In turn, there are also several factors influencing individual size. I tested how individual size, growth, size distribution and population density in seven single species populations of brown trout (Salmo trutta) influence both individual fecundity and population fecundity in seven small oligotrophic lakes located near Stekenjokk. The field work was conducted in the summer of 2021 by Pär Byström with colleagues where brown trout were caught with gillnets. My results show that individual size and growth had an influence on both the number of eggs as well as the size of the eggs while population density did not. This is suggested to be a result of either a trade-off between the number and size of eggs or possibly a display of the higher metabolic cost following being a large sized brown trout.