Figure 1

Gyrodactylus salaris Malmberg, 1957 on two strains of Atlantic salmon Salmo salar L. Experimental infection of G. salaris (Fusta strain, haplotype A) on (A) S. salar (n = 30; three replicates of 10 fish each), from the River Dee in Wales, UK; and (B) the control group of S. salar (n = 10) from the River Lærdalselva, Norway. The growth on the two hosts (Welsh and Norwegian S. salar populations) is shown on the same scale for direct comparison. Grey dotted lines represent the number of parasites assessed on each individually marked fish; mean intensity of infection is shown in blue line, including standard error of the mean (SEM).