First report of Gyrodactylus teuchis (Monopisthocotyla: Gyrodactylidae) in farmed rainbow trout Oncorhynchus mykiss from Eastern Europe

Gyrodactylus teuchis is a widespread in Western and Central Europe parasite of wild and farmed salmonid fishes. We recorded this parasite species on one-year-old caged rainbow trout Oncorhynchus mykiss from Lake Kalmozero (White Sea drainage system, Republic of Karelia, Russia) in May and October 2023. The infection prevalence was 100% and 75%, and the mean abundance was 20.8 and 18.1 ind., respectively. Morphological identification of these specimens was confirmed by molecular data on the mitochondrial cox1 gene. This is the first report on G. teuchis finding in the White Sea drainage basin as well as in cage-reared rainbow trout in Russia.