The Shasta River watershed is a major tributary to the Klamath River in northern California and provides critical habitat for federally and state-listed Southern Oregon/Northern California Coast coho salmon (Oncorhynchus kisutch), as well as Chinook salmon (O. tshawytscha), steelhead (O. mykiss), and Pacific lamprey (Entosphenus tridentatus). Despite the watershed’s volcanic geology that supports coldwater spring emergence, coho salmon populations in the Shasta River remain low due to a variety of factors including elevated summer water temperatures outside of spring-fed reaches, limited low-velocity and off-channel habitats for overwintering, and reduced floodplain connectivity.
California Trout’s Shasta River Oxbow Habitat Improvement Project focused on reconnecting and enhancing a historic oxbow channel to improve rearing habitat for native salmonids. Project partners restored hydraulic connectivity between the mainstem river and off-channel floodplain features, allowing water to move through the oxbow across a broader range of flows. Improvement activities included grading and channel excavation to reestablish flow paths, as well as refining inlet and outlet conditions to promote consistent connectivity. Habitat improvements were made to maintain suitable water depth and, by placing woody debris throughout the oxbow and mainstem, to sustain ideal velocity conditions for juvenile fish.
FISHBIO conducted pre- and post-construction monitoring surveys to evaluate habitat conditions, connectivity, and fish use within the reconnected oxbow. Water velocity and depth in both the mainstem and oxbow were measured using an Acoustic Doppler Current Profiler (ADCP). Topographic changes and floodplain extent before and after the habitat improvement effort were documented using time-lapse game cameras, ground-level photo point surveys, and aerial photo and video point surveys. FISHBIO staff also collected environmental DNA (eDNA) with Jonah Venture eDNA kits to confirm the presence or absence of salmon species in or upstream of the oxbow before and after habitat improvement. Post-monitoring habitat assessments indicate that the site provides low-velocity, moderate-depth habitat well suited for juvenile rearing. Early observations/results suggest that a substantial portion of the oxbow meets target habitat criteria and is actively utilized by fish. Ongoing monitoring will continue to inform project performance and contribute to a broader understanding of the effectiveness of off-channel habitat reconnection in the Shasta River system.