OF FRESHWATER FISH ASSEMBLAGES

(wileyonlinelibrary.com) DOI: 10.1002/rra.1308et al., 2005). In rivers, fragmentation is easy to accomplish since a single damming event is enough to isolate adjacent river segments (Jager et al., 2001). The impacts of large dams (i.e. height> 15m as defined by Poff and Hart, 2002) on fish are well documented. The obstruction of the dispersal and migration of organisms is its most discussed effect (e.g. Saunders et al., 1991; Dynesius and Nilsson, 1994; Peter, 1998; Nilsson et al., 2005), being directly linked to loss of populations and entire species of freshwater fishes, but it is easy to find studies reporting other significant impacts of these structures on the aquatic ecosystems, namely the changes on the habitat characteristics from a lotic to a lentic environmen