Brook Trout and Dead Trees: Year 1

John A. Sweka and Kyle Hartman, Division of Forestry, West Virginia University, P.O. Box 6125, Morgantown, WV26506.

Abstract: Large woody debris (LWD) is an important fish habitat component in small stream communities. The objective of our study is to determine if the artificial addition of LWD by loggers can improve stream habitat quality and enhance brook trout (Salvelinus fontinalis) populations in Appalachian streams where riparian sources of LWD have been reduced by past logging activity. Such additions may prove to be a useful mitigation tool to the timber industry in the future.

The first year of the study (fall 1999 - summer 2000) assessed initial habitat parameters and brook trout populations in eight streams in the Middle Fork River watershed, WV. Principal component analysis (PCA) and correlation analysis were used to assess variability between streams with respect to habitat variables and to correlate brook trout population data to such variables. Brook trout population variables (numbers, density, and biomass) were most strongly correlated with the principal component comprised of the number of functional pieces of LWD, percent substrate composition of boulders, and percent substrate composition of fine sediment. Partial correlation of brook trout density and biomass showed significant correlations to the number of functional pieces of LWD (density: r = 0.99, p = 0.01; biomass: r = 0.98, p = 0.02). These initial results illustrate the importance of habitat created by LWD to brook trout populations.

LWD of diameters > 10 cm and lengths > 5 m are believed to contribute the most to creation of pool habitat (Flebbe and Doloff 1995). In August 2000, the logging crew targeted trees which fit this size class criteria, and felled 5-6 trees per 100 m in either 900 m or 300 m reaches in the eight study streams. This size class of LWD was increased by an average of 89 - 153 % in these stream reaches. Changes in stream habitat and brook trout population responses to the LWD additions will be monitored over at least the next three years.

Flebbe, P.A. and C.A. Dolloff. 1995. Trout use of woody debris and habitat in Appalachian wilderness stream of North Carolina. North American Journal of Fisheries Management 15: 579-590.