Open Collections

Abstract

Line Creek is an important spawning tributary for Bull Trout (BT; Salvelinus confluentus) inhabiting the Elk River upstream of a migratory barrier at Elko BC. Ongoing fisheries monitoring has shown BT spawning to be associated with the glide (i.e. pool/tail-out) habitat typically created by large woody debris (LWD) jams. In June 2013, a large flood mobilized and removed much of the functional instream LWD from Line Creek. Results from annual monitoring confirmed the loss of LWD and associated pool habitat, as well as the lowest BT spawning counts on record. In 2014, we completed a multi-scale characterization of BT spawning locations in Line Creek to document habitat characteristics at watershed, reach, and channel unit scales. This study successfully described preferred spawning use in certain areas of the watershed, reaches of the creek, and specific habitat units. Hydraulic conditions were also described at observed spawning sites within individual habitat units. At the habitat unit scale, we were able to develop a Habitat Suitability Index (HSI) based on water depth, water velocity, and vertical hydraulic gradient. This information was applied to rehabilitation designs at a variety of scales. At the watershed scale, this study has guided work into portions of the watershed suitable to BT spawning (corroborated by previous assessments) and guided work along reaches that lack the preferred habitat attributes required to support spawning. At the habitat unit or rehabilitation structure scale, these results coupled with habitat assessments are informing the designs of LWD structures that mimic the natural jams displaced in June 2013. Rehabilitation work in Reach 1 of Line Creek was completed in summer 2017.