Riverine environments present specific barriers and challenges to dispersing fish, depending on their dispersal capability. While some barriers are obvious and finite (for example a waterfall), the subtle influences of dendritic river network structure can also affect the dispersal, and therefore the genetic structure, of freshwater fish within river catchments. In addition to these natural barriers, artificial barriers like weirs and dams can have significant effects on the flow of genes between populations in rivers. In order to achieve the effective management and conservation of populations there is a need to understand dispersal and how the movement of individuals impacts populations at a variety of scales. Studies of dispersal are important for the perspective they bring to the movement and migration of individuals and the subsequent flow of genes – both temporally and geographically. It is this spread of genes that largely determines the genetic diversity of populations, which is a quality necessary for the stability and persistence of individuals and populations.