Effects of Large Woody Debris Addition on Wild Brook Trout and In-Stream Habitat in Western Maine

We evaluated the effects of large woody debris (“LWD”) addition on habitat and population metrics of wild brook trout in twelve 1^st – 2^nd order streams in the Mahoosuc Range of the White Mountains in western Maine, USA. In 2007 and 2008, we treated 2 km stretches of six streams at a rate of 1 LWD piece / 5 m; we selected six nearby streams to serve as reference sites. Brook trout sampling occurred twice yearly and habitat surveys occurred once yearly from 2007 - 2010.  We sampled all treated streams 1 – 3 times prior to, and 3 – 6 times subsequent to, LWD addition. Natural abundance of LWD in streams was extremely low (mean ± 2 S.E.: 1.1 ± 0.6 pieces / 200m). Two years after LWD addition, treatment sites contained twice the abundance of LWD pieces than did reference sites (19 ± 3. 6 pieces vs. 8.5 ± 2.8), but there was no difference in the abundance of pools (12 ± 1.5 vs. 13 ± 1.7 pools / 200 m). Brook trout density (range: 0.02 ± 0.001 fish/ m² to 0.47 ± 0.15) and biomass (range: 0.3 ± 0.15 g/ m² to 6.1 ± 2.9) was highly variable over time and among sites, and effects of LWD were not clear. In 5 of 6 treated sites, trout abundance and density declined sharply after treatment but recovered above pre-treatment levels 3 years subsequent, but metrics in 3 of 6 reference streams also increased during the course of the study. A longer time series of data is necessary to evaluate the efficacy of LWD addition in increasing abundance and biomass of brook trout.