The susceptibility of Salvelinus namaycush (Walbaum) to Gyrodactylus salaris Malmberg (Platyhelminthes; Monogenea) under experimental conditions

Abstract

The host specificity of Gyrodactylus salaris was studied with respect to its ability to infect Lake trout (Salvelinus namaycush) under experimental conditions. Lake trout exposed to heavily infected salmon for 6 days became infected but at a low intensity compared to previous results from salmon. The Lake trout were divided into two groups on basis of the course of infection and parasite survival on individually isolated fish: (1) Hosts receptive to parasite attachment but refractive to parasite reproduction (maximum infrapopulation survival time, 21 days post-isolation); (2) Hosts receptive to parasite attachment and reproduction, but which, after a short period of parasite population growth, eliminated the parasite (maximum infrapopulation survival time, 28 days post-isolation). The parasite population declined directly after isolation of two replicated groups of 50 Lake trout each, in contrast to ca. 50% of the individually isolated Lake trout (group 2 above). This shows the necessity of experimental observations of the course of infection on individually isolated hosts for information on parasite reproduction. No G. salaris-induced host mortality was observed.