Distribution of the gill parasite Discocotyle sagittata (Monogenea: Polyopisthocotylea) in parr of Atlantic salmon Salmo salar and sea trout S. trutta in Norwegian rivers

The monogenean gill parasite Discocotyle sagittata is reported from parr of Atlantic salmon Salmo salar and sea trout S. trutta in the anadromous part of 86 out of 223 Norwegian rivers. The prevalence in each river varied from 1.5% to 88.9%. This study has significantly increased our knowledge about the occurrence of this salmonid parasite in Norway. Most likely, D. sagittata has a much wider distribution all over the country and probably also occur in numerous inland lakes, rivers and streams.