Phenology of fish spawning in two lakes that are heated to different degrees

Abstract The aim of this paper is to present the results of studies on the phenology of the spawning of fish in two lakes with different degrees of heated waters. The studies performed indicated that heating the waters distinctly hastened fish spawning in comparison to the same species of fish inhabiting waters with normal thermal conditions. Spawning usually occurred two to three weeks earlier in the heated Lake Licheńskie than it did in Lake Ślesińskie, which has waters with a natural thermal regime. Additionally, it was noted that fish spawning lasted longer in waters with higher temperatures.