Migration Patterns of Pikeperch (Sander lucioperca) in Byälven River Swede

Migration is an important behavior in many fish species and serves several functions, ranging from defense and foraging to reproduction. This study used telemetry to investigate whether pikeperch (Sander lucioperca) migrate between Lake Vänern and the Byälven River. Furthermore, the study examined whether migration speed differed between river and lake habitats and whether movement direction (upstream vs. downstream) affected speed. Acoustic receivers (N=18) were deployed in the lower 80 km of the Byälven River in mid-April and retrieved in October. Pikeperch were caught in Harefjorden, implanted with acoustic transmitters, and then released back into the water. Their movements were recorded and analyzed. The analysis of migration speed showed no significant differences between upstream and downstream movement, nor between river and lake habitats. The pikeperch migrated upstream from Harefjorden approximately 7–9 km, with some individuals continuing up to 19 km, before the majority (5 out of 7) eventually moved toward the river mouth. The study suggests that pikeperch migrate between Lake Vänern and the Byälven River, likely in connection with reproduction. The migration pattern of the Byälven-migrating pikeperch indicates that it has preferred spawning areas that can be important for its reproduction and should therefore be considered in management efforts to maintain a viable pikeperch population.