Gyrodactylus salaris – kartlegging i Drammensregionen
Overvåkingsprogrammet utredet om Gyrodactylus salaris finnes på fiskebestander i innsjøer og elver som drenerer til Drammenselva.
This report presents results from a surveillance programme that aims to map the potential occurrence of Gyrodactylus salaris on fish hosts upstream of the anadromous parts of River Drammenselva and River Lierelva. The aim in 2017 was to assess whether rainbow trout is present in the Begna watercourse and if this host carries G. salaris. Further, the presence of G. salaris on Arctic char in Lake Randsfjorden was evaluated.
Environmental DNA (eDNA) samples (water filtrates) were obtained from several localities within the catchment area. None of the samples from sites not influenced by waste water from rainbow trout farms tested positive for rainbow trout DNA. This indicates that rainbow trout is not a naturally occurring species in these parts of the Drammenselva catchment. Negative results from electro fishingsupports this conclusion.
G. salaris was not detected in eDNA samples from the Begna watercourse. However, the parasite was detected in field samples from River Lierelva, a river with a known presence of G. salaris, which was therefore chosen as a positive control. This is the first time the presence of G. salaris has been successfully detected from environmental samples using the eDNA methodology. G. salaris was not detected in any of 500 samples of arctic char obtained from Lake Randsfjorden.