Resource managers add large woody debris (LWD) to streams to improve spawning habitat for coho salmon, but we still know little about how closely salmon build their redds (spawning nests) to that wood and if restoration-sourced LWD provides preferential spawning locations.

Researchers used mapped redds from three wet seasons (2014 - 2015, 2017 - 2018, and 2021 - 2022) and analyzed them with maximum‑entropy (MaxEnt) models. Five variables were tested: drainage area (A), reach‑scale slope (Sr), fine‑scale 1m² slope (Sm), and distance to both natural (LWDdr) and installed (LWDdi) wood. Model cohorts used 250 bootstrap replicates and were rated with area under the curve (AUC) and true skill statistic (TSS).

Models were highly performative (mean AUC 0.916 – 0.964; TSS 0.574 – 0.764). Drainage area and both measures of slope were strongest predictors of redd presence. Fine‑scale slope consistently improved the models and was critical in steep inner‑gorge reaches. Distances to installed LWD provided smaller, context‑dependent gains that increased when redds lay very close to wood, confirming contribution of installed LWD to coho spawning decisions.

Overall, coho redd occurrence in this headwater network is governed by basin size and channel slope; proximity to LWD acted as secondary but significant determinants.