Toward a Framework for Characterizing Hydrologic Connectivity in Riverine Fishes

Hydrologic connectivity is a critical component of habitat quality for riverine fishes that move long distances. The stream network is the foundation upon which stream habitats are organized. How aquatic ecologists address habitat organization within the context of dendritic stream systems is a research question open to discussion and opportunity. We reviewed how hydrological connectivity has been studied for migratory salmonids. Our analysis indicated three main themes of study that related to: 1) relatively stable connections 2) dynamic connections and 3) anthropogenic influences on hydrologic connectivity. Challenges unique to understanding connectivity for river fishes include the complexity of hydrologic connectivity (the force and direction of flow, scale-dependent effects), the constraints of movement isolated within a stream network, and human influences. However, we also identified that work is currently under way that includes network structure and river discharge in analyses, increases the temporal scale of hydrologic analysis, and that distinguishes between natural processes and human influences. We are optimistic that aquatic ecology is poised to progress with a more holistic approach that addresses the fundamental importance of the dendritic structure of rivers in tackling the diversity of science and management issues facing aquatic dependent populations.