README_DataSet Vejrik et al.xlsx

Trophic position of the species and site trophic state affect the foraging behavior: from apex predator to herbivore

The impact of trophic position of the species and site trophic state on the (i) total niche width (TNW), (ii) individual niche width (INW), and (iii) individual specialization (IS) was studied using an innovative approach. Stable isotopes (δ13C, δ15N) of four body tissues differing in isotopic turnover rates were used from four freshwater fish representing the entire food web: European catfish (Silurus glanis), Northern pike (Esox lucius), Eurasian perch (Perca fluviatilis), and rudd (Scardinius erythrophthalmus). TNW was largest and narrowest for the apex predator (European catfish) and obligate predator (Northern pike), respectively. INW exhibited a polynomial trend for European catfish, Northern pike and Eurasian perch (representing mesopredator), it decreased with body mass, but then increased after exceeding a certain species dependent body mass threshold. Thus, for ectothermic species, apex predator status is not strictly linked to the species but to the size of individuals. In herbivores (rudd), INW increased with body mass. IS of predators negatively correlated with site trophic state. Thus, human-induced eutrophication can significantly change the foraging behaviors. The trends can be generalized to other species at similar trophic positions in either aquatic or terrestrial systems.