The aim of the research was to test relative weight (Wr). a condition index which allows evaluation of fish well-being. as a tool to investigate the impact of the presence of non native species (NNS) on the condition of the key native species (NS) of the Tiber River basin (Italy): Barbustyberinus Bonaparte. Leuciscus cephalus (Linnaeus). https://fitnessgravesyardes.shop/product-category/mechanical-safety-switch/