Are hybrids between Atlantic salmon and brown trout suitable long‐term hosts of Gyrodactylus salaris during winter?

• Published in: Journal of Fish Diseases
• Main Authors: Knudsen, R, Henriksen, E H, Gjelland, K Ø, Hansen, H, Hendrichsen, D K, Kristoffersen, R, Olstad, K
• Other Authors: Universitetet i Tromsø
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Veterinary (miscellaneous); Aquatic Science; Atlantic salmon; Salmo salar; Subarctic
• Online Access: http://dx.doi.org/10.1111/jfd.12602; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjfd.12602; https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfd.12602

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.