Habitat use and temporal dynamics of blackwater stream fishes in and adjacent to beaver ponds

We sampled stream fishes within and at varying distances from beaver ponds for two years in two southeastern blackwater streams. Our objectives were t o determine whether species showed ontogenetic or seasonal shifts in habita t use involving impounded and free-flowing stream reaches and whether assem blage structure and dynamics varied between ponds and streams and as a func tion of upstream distance from ponds. Age-0 and adults of most of the more abundant species (15) were collected in either streams or ponds, suggesting no ontogenetic or seasonal shifts in habitat use for these species; The pr oportions of age-0 to adult fish of four species were higher in ponds than streams, suggesting movement of adults to ponds to breed. The proportion of age-0 to adult Erimyzon oblongus was higher in streams when compared to po nds, suggesting adults of this species supplement food re sources by feedin g in ponds. Assemblage structure was less stable in ponds when compared to streams. In streams, age-0 and adult fish densities and population coeffici ents of variation (cv) declined with upstream distance from ponds. Because high CVs were typical of species occurring in streams throughout their life , and habitat structure and variability were not related to upstream distan ce from ponds, interactions between pond boundaries and fish movement are p robably responsible for the patterns we observed in streams adjacent to pon ds.