Changes in efficiency of natural reproduction and survival of fish larvae in heated Konin lakes

Abstract

In 1966 -1992 studies were undertaken on the influence of a long term heating of lakes upon the efficiency of natural reproduction and survival of fish larvae. It was found that conditions of spawning grounds deteriorated and that species less resistant to temperature and water flow (pike) and to water flow only (tench and crucian carp) disappeared. A decreasing trend of both the level of fry numbers as well as the level of species numbers, including the disappearance of species, was noted. The exception was chub showing the tendency of increasing the numbers.