The hydrological regime of Lac Saint-Jean (Québec, Canada) was drastically altered following the installation of dams along its drainage channels in 1926. This article examines the impact of water level management on the spawning success of yellow perch (Perca flavescens) and northern pike (Esox lucius). An analysis of water levels over the past 100 years shows a decrease in the amplitude of spring flooding since 1926, which has likely contributed to a reduction in the effective size and quality of spawning sites. It also highlights a delay in the time taken to reach the maximum spring high water level. Historical temperatures of the lake and associated wetlands allowed the spawning period between 1991 and 2015 to be estimated, and underlined the impact of low spring water levels on wetland accessibility. Presently, spawning sites for the study species are only partially flooded during the breeding season. It is recommended that a water level management plan be adopted that allows higher water levels to be reached earlier in the spring; that keeps the spring level stable to promote hatching and to ensure the survival of fry during early life stages; and that increases the difference between spring and summer water levels.