Across all biomes, habitat fragmentation, loss and degradation are frequently cited as main causes of species decline and extinction (Bascompte and Sole, 1996; Doak, 1995; Ehrlich, 1995; Fahrig, 2002). In freshwater ecosystems, fragmentation and flow regulation have severely degraded many of the world's rivers (Revenga et al., 2000; Nilsson et al., 2005). River regulation typically results in reduced habitat heterogeneity, a loss in lateral and longitudinal connectivity (Mann, 1988; Haslam, 1990), and an altered flow regime (Lytle and Poff, 2004). The impact of these changes to the natural functioning of river systems are often manifested in reduced diversity of aquatic organisms.