Transactions oj the American Fisherien Sodety 124:613-622. 1W5 American Fisheries Society Ebb and Flow of Encroachment by Nonnative Rainbow Trout in a Small Stream in the Southern Appalachian Mountains

Abstract.—Brook trout Salvelinus fontinalis is the native salmonid species of streams in the southern Appalachian Mountains. The present distribution of this species, once widespread from headwaters to lower reaches of large streams, is restricted to mostly headwater areas. Changes in the distribution of native brook trout in the presence of nonnative rainbow trout Oncorhyncluts mykiss have been documented in Great Smoky Mountains National Park. When rainbow trout were first found in a tributary (Rock Creek) in the park in 1979. a study was begun to assess changes through time in distribution and abundance of rainbow (rout in Rock Creek and to compare the brook trout and rainbow trout associations in Rock Creek with associations found in other park streams. Abundance of brook trout was low in the downstream sections of Rock Creek in 1979-1993. Brook trout abundance was highest in the steep-gradient, pool-dominated headwater section which was only 2 km from the confluence of Rock Creek and Cosby Creek. Rainbow trout were present in low densities in Rock Creek during the same period. Although rainbow trout were most abundant in the lower stream sections and never found in the headwater section, adult and agc-0 rainbow trout were found in the middle section in 1988. Rainbow trout were absent in the middle section in 1991. but one large adult rainbow trout was present in the section in 1992 and 1993