Habitat fragmentation resulting from human activities is a major factor contributing to reductions in biodiversity and species abundance worldwide. When movements are restricted, subpopulations become isolated, leading to reduced breeding opportunities, inbreeding depression, and interruption of key life stages. This problem is particularly ubiquitous in riverine ecosystems, where dams, water diversions, culverts, and other structures create barriers to movements of aquatic organisms. Because these organisms are unable to leave their streams to bypass obstacles, and because the bifurcating structure of stream networks precludes the use of alternate pathways to needed habitats, this type of fragmentation can quickly lead to loss of species richness, and compromised ecosystem function (Morita and Yamamoto, 2002; Morita and Yokota, 2002).