Structure of Aggressive Behavior in Underyearlings of the Rainbow Trout Oncorhynchus mykiss (Salmonidae) Changes under the Influence of Diplostomum pseudospathaceum (Trematoda) Parasites

Abstract The dynamics of aggressive behavior the underyearlings rainbow trout Oncorhynchus mykiss infected with metacercariae trematodes Diplostomum pseudospathaceum has been studied in an experimental heterogeneous environment for 48 days. fish competed dark area bottom by charges, biting, chasing, and frontal lateral displays. sharply increased aggressiveness when parasites became infective (1.0–1.5 months after infection), i.e., capable infecting final host (piscivorous birds), manifested itself frequency bites (more than 20 times compared to control) charges (almost three times) was accompanied fast movements, sharp maneuvers, low ability compete shelters. share comparatively slow displays chasing much smaller. strategy D. manipulation consists two stages: (1) protecting from predators; (2) increasing vulnerability host. At first stage, general level aggression decreases sharply; at second, on contrary, rapidly increases, but ratio different categories changes. that make more vulnerable predators increases. High activity competitiveness contribute their rapid extermination or moving another habitat. Such migration can increase fitness parasite, facilitating its dispersal water body.