The biomass and production of pike perch and whitefish in two small lakes in southern Finland

Abstract

In two small forest lakes total fish biomass was 73 kg/ha and 32 kg/ha, and fish production 30 and 16 kg/ha, respectively. The fish of the first lake were perch, pike and introduced whitefish, of the second perch and whitefish. The main reasons for the differences in fish biomass and production were probably light and oxygen conditions. The diet segregation between perch and whitefish, which reduced inter specific competition, and predation by pike on perch, which reduced intraspecific competition for food among perch, also resulted in improved fish production in the first lake.