Long‐Term Increases in Trout Abundance following Channel Reconstruction, Instream Wood Placement, and Livestock Removal from a Spring Creek in the Blackfoot Basin, Montana

Abstract

AbstractTo restore habitat for wild trout, Kleinschmidt Creek, a low‐gradient, groundwater‐dominated stream in the Blackfoot Basin, Montana, was reconstructed using natural channel design principles. Reconstruction increased stream sinuosity from a ratio of 1.1 to 1.6, decreased mean channel width from 14.5 to 2.8 m, and increased sediment transport capacity to reduce accumulations of fine instream sediment. To further improve trout habitat, coarse woody debris (CWD) was variably placed within the new channel and livestock were excluded to promote the vegetative recovery of the riparian area. To evaluate the response of wild trout (92% Brown Trout Salmo trutta) to channel restoration, the abundance (number of trout per linear meter) and biomass (g/linear m) of age 1+ trout were monitored for 15 years (1998–2012) in a reach with low density CWD (1.3 stems/100 m) and compared with regional (reference) trends. Posttreatment (2002–2012) trout numbers in the low‐density CWD reach were also compared with those in a reach with high‐density CWD (18.2 stems/100 m). Long‐term trends for the reference reaches showed a significant negative trend in trout abundance and no significant trend for biomass. Long‐term trends for the low‐density CWD reach showed a significant positive trend in abundance, as well as a significant trend in biomass. Trout abundance and biomass increased over the posttreatment period in the low‐density CWD reach. However, in the high density CWD reach, while posttreatment abundance increased significantly, there was no significant trend in biomass. These results demonstrated that channel restoration increased wild trout populations in a deep, narrow, vegetated stream and that instream wood provided primarily short‐term benefits during the early phase of habitat recovery.Received November 26, 2013; accepted October 18, 2014