infections on resident Arctic charr (Salvelinus alpinus)

• Main Authors: Gyrodactylus Salaris (monogenea, Tor A. Bakke
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Draget; Arctic charr; Salvelinus alpinus
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.530.5069; http://folk.uio.no/bachmann/Publications/Robertsen et al - EBOF 2008.pdf

Abstract This study surveys the distribution of Gyrodactylus salaris on resident Arctic charr, Salvelinus alpinus, in lakes connected to three south-Norwegian watercourses: Numedalsvass-draget, Skiensvassdraget and Hallingdalsvassdra-get. Gyrodactylus salaris infected charr was only recorded in Numedalsvassdraget. The parasites had the same mitochondrial haplotype as those previously reported on charr in Lake Pålsbufjor-den, which is part of Numedalsvassdraget. Since the G. salaris-charr association is persistent in Pålsbufjorden and has a wide distribution above the stretches of the watercourse inhabited by anadromous salmonids, this is considered a stable, although perhaps relatively young, host-parasite system. More detailed analyses of these interac-tions revealed seasonal variations in the parasite population dynamics between late summer and late autumn, with heavier infections occurring in males and older fish in October. This is explained by the combined action of seasonal differences in temperature and physiology and ecology of host cohorts. It is assumed that the occurrence of G. salaris on charr in Pålsbufjorden resulted from a host switch to charr from rainbow trout, Oncho-rynchus mykiss. Host switches may cause signifi-cant expansions of the geographical range of pathogenic variants of G. salaris. Therefore, obser-vations of frequently occurring G. salaris on charr have implications for the diagnosis, management and control of salmonid gyrodactylosis.