Beamer, E.M., Seixas, G., Veldhuisen, C., Hood, G. and Ramsden, K., 2023. Habitat status and trends results to evaluate life stage and population responses of Skagit River Chinook Salmon to recovery actions. Skagit River System Cooperative, Burlington, WA. pp. 53.

Chinook Salmon recovery requires a combination of many local actions that are expected to result in a population response that can be masked by variability in environmental factors also influencing the population positively or negatively. Thus, tracking habitat conditions, recovery actions, environmental factors, and population trends is critical to understanding the efficacy of Chinook Salmon recovery in the Skagit River. Habitat status and trends (HST) monitoring was implemented using remote sensing and field verification methods throughout the Skagit Basin with the intention of tracking recovery actions aimed at influencing habitat conditions. This report describes the methods and findings from HST monitoring within the Skagit River watershed and its estuary spanning a 30-year period from before adoption of Puget Sound Chinook recovery plans through the first 15 years of its implementation. Ultimately, our goal is to integrate these habitat status and trends results with an existing long-term multiple life stage Skagit Chinook Salmon dataset to evaluate how salmon recovery actions have influenced the population dynamics of Skagit Chinook Salmon through an Integrated Population Model (IPM) framework.
Chinook Salmon spawning and rearing habitat has improved throughout the Skagit River basin due to a combination of restoration and natural changes. We found a ‘salmon recovery success story’ for recovery actions aimed at improving watershed conditions related to forestry management. Treatment of forest roads and improvements in avoiding logging of sensitive landforms appear to have reduced landslides throughout the watershed. Additionally, we found extensive restoration has been completed within the Chinook Salmon freshwater and estuary rearing ranges. For both areas (freshwater and estuary) habitat extent has increased due to restoration and natural causes, and for both areas we also observed natural losses of habitat extent. Within freshwater, channel migration across floodplain areas sometimes resulted in reach level losses, but often resulted in gains. In the estuary, natural losses were mostly along the estuary’s seaward edge.
Restoration projects known to be present were only partially detected using HST data and orthophotos. Some reasons for imperfect detection include (a) methodological reasons, such as an inability to observe a fish barrier improvement through remote sensed imagery alone, and (b) lags in habitat response to restoration, such as for riparian planting projects where it takes multiple years to observe the vegetation change on remote imagery.
Restoration projects that improve fish passage, reconnect channels and/or tidal wetlands, or excavate channels are expected to have relatively immediate benefits for juvenile salmon, but many other restoration project types will have ‘delayed’ benefits. For example, riparian planting project benefits will occur after plants have grown to a state where their ecological functions can be expressed, which can be a few years for shading a small stream or many decades for large woody debris recruitment. Another example is the influence of reduced landsliding due to forest road treatments. The effects of reduced landsliding on egg-to-fry survival may be lagged by a few years, but the effects on pool filling and channel simplification may be lagged by multiple decades.