Stream habitat connectivity in the Canadian Arctic: an on-site approach to design and construction

Abstract

We developed a successful on-site approach for design and construction of stream modifications that addressed challenging remote-site conditions of limited field data and available construction materials. Fish habitat connectivity enhancements were constructed within an Arctic headwater stream containing a naturally impassable cascade section with 13% slope, which was bypassed in a newly constructed channel at 5% slope with nature-like fishpass structures. Primary design considerations included (1) creating suitable hydraulic characteristics for fish passage in periods of high and low discharges; (2) reducing drop heights and creating unimpeded flow paths; (3) improving hydraulic complexity for a variety of stream habitats; and (4) salvaging and incorporating vegetation disturbed from construction activities into riparian and in-stream habitat structures. In high gradient reaches (2.5%–5%), we constructed boulder weirs, boulder chokes, and deflection boulders to overcome migration impediments. In medium gradient reaches (1.5–2.5%), rock ramps, boulder chokes, and deflection boulders were constructed to control hydraulic characteristics to ensure an unimpeded flow path, suitable hydraulic complexity, and resting zones. At lower gradients (<1.5%), we incorporated a softer approach using riparian vegetation and in-stream woody debris to ensure a similar quality of fish habitat as created in the higher gradient reaches. Initial hydraulic responses to the modifications indicated this reconstructed channel provided suitable hydraulic and habitat characteristics for habitat connectivity throughout the entire stream. Our findings advance understanding of headwater stream hydraulics in the Canadian Arctic and will assist in designing future stream restoration and fish habitat compensation projects on small and remote systems. This case study supports the feasibility of successfully constructing future habitat compensation projects in challenging remote environments when using an on-site, adaptive design and construction approach.

Arctic Grayling Movements through a Nature‐Like Fishpass in Northern Canada

“…Grayling in low-gradient Barrenlands streams (see also Courtice et al 2014). Furthermore, for these larger Arctic Grayling (≥150 mm), the probability of a passage event through the M2S nature-like fishpass was not related to fish FL.…”

“…at northern latitudes, rapid increases in discharge and stream velocity during freshets have frequently been cited as critical cues for spring movements (Gustafson 1949;Witkowski and Kowalewski 1988;Northcote 1995;Jones et al 2003a). Indeed, Arctic Grayling often spawn in small streams during freshets (Northcote 1995;Stewart et al 2007), the onset of which is rapid, variable in timing among years, and of short duration (i.e., 5-10 d; Jones et al 2003a;Courtice et al 2014). Moreover, field observations suggested that Arctic Grayling appear in streams and fishpasses almost immediately after the freshet begins (Cahill et al 2015).…”

“…Subsequent evaluations of the three fishpasses showed that only a single, nature-like choke-pool fishpass allowed for fish movement (Courtice et al 2014;Cahill et al 2015). Cahill et al (2015) evaluated the performance of the nature-like fishpass for Arctic Grayling and found that the upstream attraction and passage efficiencies were higher than the downstream attraction and passage efficiencies.…”