title: Are hybrids between Atlantic salmon and brown trout suitable long-term hosts of Gyrodactylus salaris during winter?
abstract: The monogenean parasite Gyrodactylus salaris poses serious threats to many Atlantic salmon populations and presents many conservation and management questions/foci and challenges. It is therefore critical to identify potential vectors for infection. To test whether hybrids of native Atlantic salmon (Salmo salar) × brown trout (Salmo trutta) are suitable as reservoir hosts for G. salaris during winter, infected hybrid parr were released into a natural subarctic brook in the autumn. Six months later, 23.9% of the pit-tagged fish were recaptured. During the experimental period, the hybrids had a sixfold increase in mean intensity of G. salaris, while the prevalence decreased from 81% to 35%. There was high interindividual hybrid variability in susceptibility to infections. The maximum infrapopulation growth rate (0.018 day-1) of G. salaris throughout the winter was comparable to earlier laboratory experiments at similar temperatures. The results confirm that infrapopulations of G. salaris may reproduce on a hybrid population for several generations at low water temperatures (~1 °C). Wild salmon-trout hybrids are undoubtedly susceptible to G. salaris and represent an important reservoir host for the parasite independent of other co-occurring susceptible hosts. Consequently, these hybrids may pose a serious risk for G. salaris transmission to nearby, uninfected rivers by migratory individuals.
authors.affiliation: Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Knudsen
authors.affiliation: Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: E H
authors.initials: EH
authors.lastname: Henriksen
authors.affiliation: Fram Centre, Norwegian Institute for Nature Research, Tromsø, Norway.
authors.forename: K Ø
authors.initials: KØ
authors.lastname: Gjelland
authors.affiliation: Norwegian Veterinary Institute, Oslo, Norway.
authors.forename: H
authors.initials: H
authors.lastname: Hansen
authors.affiliation: Norwegian Institute for Nature Research, Trondheim, Norway.
authors.forename: D K
authors.initials: DK
authors.lastname: Hendrichsen
authors.affiliation: Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: R
authors.initials: R
authors.lastname: Kristoffersen
authors.affiliation: Norwegian Institute for Nature Research, Lillehammer, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Olstad
mesh_terms: D000818:Animals; D004198:Disease Susceptibility / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary; D005393:Fish Diseases / Q000453:epidemiology* / Q000469:parasitology; D006790:Host-Parasite Interactions; D006824:Hybridization, Genetic; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D020317:Salmo salar / Q000235:genetics; D012621:Seasons; D014200:Trematoda / Q000502:physiology; D014201:Trematode Infections / Q000453:epidemiology* / Q000469:parasitology / Q000662:veterinary; D014337:Trout / Q000235:genetics
keywords: Salmo salar × Salmo trutta hybrids; host-parasite dynamics; hybrid susceptibility; seminatural experiment; transmission