Basinwide visual estimation techniques were used to inventory habitat and fish populations in three Shenandoah National Park watersheds having low, moderate, and high acid neutralizing capacity (ANC) to determine: a) types, distribution, and total amount of habitat; b) community structure and estimate fish density, condition, and production; and c) the influence of habitat verses ANC on fish communities. Fish species richness ranged from 3 to 7 species, and increased with ANC. Brook char (Salvelinus fontinalis) and blacknose dace (Rhinichthys atratulus) were the only two species common to all watersheds. Both species used pools more than riffles (P<0.05). Brook char density in pools increased with ANC (P<0.05), ranging from 13.1 to 40.1 fish/100m². Blacknose dace density in pools was similar between the low ANC stream (23.2 fish/100m²) and the high ANC stream (22 fish/100m²) in spring 1993, but eventually became higher in the low ANC stream (P<0.05). Annual production by brook char ranged from 23.7 to 26.4 kg/ha in the low ANC stream, from 27.7 to 39.9 in the moderate ANC stream, and from 48 to 77 kg/ha in the high ANC stream. Annual production by blacknose dace generally increased with ANC, ranging more narrowly from 0.3 to 2.4 kg/ha. Condition factor and mean weight of both species were lowest in the low ANC stream (P<0.05 for each). The effect of water acidification on movement of brook char and blacknose dace was studied in the paired channels of a laboratory stream. The objectives of this experiment were to determine the ability of the fish a) to avoid depressions in pH, and b) to use an alkaline microhabitat refuge during reductions. Both brook char and blacknose dace avoided an acidified channel and sought refuge in a refuge (P<0.05). / Master of Science