Interesting paper on the distribution of Gyrodactylus salaris.
Paladini, G., Shinn, A.P., Taylor, N.G.H. et al. Geographical distribution of Gyrodactylus salaris Malmberg, 1957 (Monogenea, Gyrodactylidae). Parasites Vectors 14, 34 (2021). https://rdcu.be/ceaca