Hydrobiological and Geochemical Responses to Trout Cage Aquaculture in Lake Ecosystem

Abstract This study examines the seasonal dynamics and relationships between geochemical and hydrobiological parameters of lake ecosystems within the impact zone of fish cage farming (Lake Ladoga, Russia). Focusing on three trout farms, environmental conditions were analysed, including water and sediment quality, benthic and zooplankton communities. Two categories of sampling sites were defined for each farm: cage and reference sites (100–600 m far from the cages). Fieldwork was conducted during four seasons in 2023: February, June, August and November. The results revealed that intensive fish feeding leads to significant organic waste accumulation under trout cages, affecting the composition and abundance of planktonic and benthic organisms. In winter, the accumulated organic matter in the sediments mineralizes, and hydrobiological indicators approach reference values. The hydrobiological and geochemical parameters analysed in this study can be used as indicators for developing ecological monitoring methods for freshwater cage aquaculture.