Newaukum Adult Salmon and Steelhead Spawner Abundance, 2020-2021

The Newaukum River basin was selected as a “pilot watershed” in 2015 by Chehalis Lead Entity to help guide and monitor salmon recovery projects in the Chehalis River basin with the goal of assessing limiting factors, data gaps, and restoration targets (http://www.chehalisleadentity.org/our-work/). Since then, both an adult and juvenile monitoring program have been implemented in the basin, allowing for adult and juvenile in-stream production estimates. This report covers the 2020-2021 survey season of intensive adult spawner monitoring in the Newaukum basin for spring and fall Chinook Salmon (Oncorhynchus tshawytscha), Coho Salmon (O. kisutch), and Steelhead Trout (O. mykiss).

A census redd (salmon nest) survey was conducted for all salmonids for the 2020-2021 season in the Newaukum basin (total escapement for Chinook and Coho Salmon in the 2020 run year and steelhead escapement in 2021 run year). However, due to the broad distribution of Coho Salmon in small creeks and tributaries with many private landowners, we were unable to completely survey all spawning habitat. The majority of spawning habitat was surveyed, and either a supplemental survey or a redd mile-1 estimate was used to expand redds for un-surveyed spawning habitat to generate a total estimate. The unsampled tributaries included in the total estimate represent areas that were historically expanded for stock assessment estimates (C. Holt, WDFW, personal communication). Major findings for the 2020-2021 season were:

• Spring Chinook adult abundance in 2020 was 4 times higher than 2019 at 700 adult spawners
• Fall Chinook abundance also increased from the previous year, although only by about 20% compared to 2019 levels at 1,063 adult spawners.
• Spring and fall Chinook spawning distribution overlapped spatially and temporally.
• Genetic analysis of run timing markers of opportunistically collected salmon carcasses showed hybridization between fall and spring run types; 75% of these heterozygotes were recovered in the main stem.
• Spring Chinook spawning occurred throughout the main stem Newaukum River, suggesting some fish may move into the lower Newaukum from the Chehalis River just before spawning. Additional effort to track spring Chinook holding patterns is needed to confirm this hypothesis.
• Fall Chinook spawned throughout the North and South Fork Newaukum River similar to 2019, but their distribution reached further upstream, most notably on the North Fork Newaukum and into some smaller tributaries like Mitchell and Lucas creeks.
• Coho Salmon increased in abundance by ~40% from 2019 and was the most abundant salmonid species in the Newaukum basin with 2,770 spawners.
• Spawn timing of Coho Salmon in the Middle Fork occurred three weeks earlier than in the North and South Fork Newaukum in 2020. Middle Fork, Kearney Creek, and Lost Creek had some of the highest spawning densities (>50 redd mile-1) with little spawning in the main stem.
• Steelhead increased by ~100 fish in 2021 compared to 2020, however the majority appeared to be hatchery fish. Steelhead were mostly distributed in the upper North and South forks of the Newaukum River with few spawning in the main stem and Middle Fork. No redds were observed downstream of the smolt trap at river mile 5.8 on of the main stem.
• The number of steelhead repeat spawners increased by 17% in 2021 compared to 2020 with zero in 2019. A similar trend of increasing repeat spawners has been observed across coastal steelhead populations in western Washington.

On average (run years 2000 to 2020), the Newaukum River contributed between 18% and 45% of the Chehalis River spring Chinook population, yet both Newaukum River and Chehalis River basin populations have declined since 2000. In 2020, the Newaukum contributed 25% to the overall spring Chinook total spawner abundance, yet this was lower than the average (29%) for the time series indicating that Newaukum River spring Chinook contribution is still below the long-term average. Through long term monitoring of the Newaukum River, our program will generate a time series of species distribution, abundance, life history diversity, and other population-level metrics (e.g., productivity) that will be valuable as restoration projects are implemented throughout the upper Chehalis Basin.