Dispersal and retention of larval fish in a potential nursery habitat of a large temperate river: an experimental study

Little information is available on governing factors of larval fish dispersal in natural river systems. Therefore, weaimed to describe dispersal and retention of marked larval nase carp, Chondrostoma nasus, along a shoreline nursery habitatof the River Danube. Based on a three-dimensional hydrodynamic model, we analyzed the influence of the hydraulic conditionson larval dispersal. We also related observed larval pathways to numerical particle tracing. Clear differences in thetemporal drift pattern were due to significant differences in the hydrodynamic characteristics of the release stations. Somelarvae remained in the study reach, most upstream of the release point. These were significantly larger than drifting larvae.We conclude that larval dispersal has an active component and that dispersal and retention patterns are dependent on thehabitat structure and hydrodynamic characteristics of the releasing points. This emphasizes the importance of links betweenthe location of spawning sites within the river and variation in flow during early development, the combination of whichmay contribute to successful recruitment of fluvial fish species.