Newaukum Adult Salmon and Steelhead Spawner Abundance, 2019-2020

The Newaukum River basin was selected as a “pilot watershed” in 2015 by Chehalis Lead Entity to help guide and monitor restoration projects in the Chehalis River basin and to determine how climate change may affect the salmonid populations in the basin (http://www.chehalisleadentity.org/our-work/). Both an adult and juvenile monitoring program have since been implemented in the basin, allowing for adult and juvenile in-stream production estimates. This report covers the first survey season (2019-2020) 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); hereafter referred to as Chinook, coho, and steelhead.

A census redd survey was conducted for all salmonids for the 2019-2020 season in the Newaukum basin (total escapement for Chinook and coho in the 2019 run year and steelhead escapement in run year 2020). However, due to the broad distribution of coho in small creeks and tributaries, we were unable to completely survey all spawning habitat in the first year. The majority of spawning habitat was surveyed, and either a supplemental survey or a redd mile-1 estimate was used to expand redds for unsurveyed 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 2019-2020 season were:

• Spring and fall Chinook overlapped in spawning both spatially and temporally, but there appeared to be some spatial and temporal separation based on densities of spring and fall Chinook in the upper South Fork Newaukum. Total spring and fall Chinook estimates for the 2019 run year were 175 and 858, respectively.
• Spring Chinook spawned throughout the main stem Newaukum River, suggesting some may move into the lower Newaukum from the Chehalis River just before spawning. Additional effort tracking spring Chinook holding patterns would be needed to confirm this hypothesis.
• Although fall Chinook spawned throughout the lower North and South Fork Newaukum River and main stem, there was a high density (12-24 redds mile-1) of fall Chinook that spawned from Leonard Rd down to Jackson Hwy in the lower South Fork Newaukum.
• Coho was the most abundant salmonid species in the Newaukum basin in the 2019/2020 run year with 1,988 spawners estimated. Middle Fork Newaukum River and Kearney Creek had some of the highest densities of spawning coho and there was little spawning in the main stem.
• Steelhead was the second most abundant species in the basin with 1,103 spawners estimated. Steelhead were mostly distributed in the upper North and South Forks of the Newaukum River with very little spawning in the main stem and Middle Fork Newaukum. No spawning occurred downstream of the smolt trap.

On average (run years 2000 to 2019), the Newaukum River contributed between 18% and 45% of the Chehalis River spring Chinook population compared to the rest of the Chehalis River basin. However, the abundance of spring Chinook has been declining in the Newaukum and Chehalis rivers since 2000, and the Newaukum River’s contribution of spring Chinook to the overall population has also been declining. With 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 that will be valuable as restoration projects are implemented throughout the upper Chehalis Basin.