Newaukum Adult Salmon and Steelhead Spawner Abundance, 2022-2023

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 2022-2023 survey season of intensive adult spawner monitoring in the Newaukum basin for Chinook Salmon (Oncorhynchus tshawytscha), Coho Salmon (O. kisutch), and steelhead trout (O. mykiss).

Redd based estimates were conducted similar to previous years with a few exceptions. Additional methods for monitoring were implemented for Chinook Salmon with the help of funding from Pacific Salmon Commission to look at the possibility of refining and improving monitoring techniques. In addition to the redd based estimates we conducted carcass mark recapture, and a trans-generation mark recapture method. The additional carcass work needed for these methods also allowed us to increase our sample size for genetic run testing. A Generalized Random-Tessellation Stratification (GRTS) method was used in combination with core index redd surveys for monitoring Coho Salmon. The redd based method using index and supplemental surveys was the same as previous years for steelhead trout. Major findings for the 2022-2023 season were:

• Spring Chinook adult abundance of 291 spawners is less than the previous two years but more than the first year of the intensive study (2019). Fall Chinook adult abundance of 383 spawners is the lowest abundance reported in over 20 years.
• Chinook run type based on genetics indicates that run timing based on the date and presence of lives on redds does not give a complete or accurate picture of Chinook run types in the Chehalis River basin. Of the samples tested, 25% were determined to be heterozygotes (i.e., spring-fall hybrids). Additional genetic testing throughout the Chehalis Basin where spring Chinook occur should be a priority.
• Distribution of Chinook shifted lower in the basin; most notably fall Chinook spawning in the lower main stem Newaukum River. Spring Chinook also showed a slight shift downstream but primarily during the later part of the run. The earliest spawning spring Chinook were still detected in the South Fork Newaukum upstream of Onalaska.
• Natural origin (NOR) Coho Salmon adult abundance was 3,860 spawners, approximately 1,000 less than the previous year but still higher than the long-term average of 2,674. However, hatchery origin (HOR) Coho Salmon adult abundance was 4,430, and for the first time the HOR component was larger than the NOR component.
• An increase in HOR spawning in previously low pHOS areas like upper NF Newaukum and Mitchell and Lucas creeks went from under 2% to over 30% in 2022, with Lucas Creek showing the greatest increase to 50% pHOS.
• Total spawner abundance of steelhead trout was 1,100 adults in 2023. Using the date method of March 15^th to distinguish NOR and HOR determined 915 and 185 steelhead, respectively. However, the March 15^th date is known to be an imperfect method for distinguishing hatchery- from natural-origin steelhead stock in the Grays Harbor basin. Utilizing the total spawners on the spawning ground and indicating an unknown proportion is of hatchery origin would be a more accurate way of reporting abundance.

The runs in 2022 revealed diminished counts for both spring and fall Chinook salmon, underscoring the importance of prioritizing restoration initiatives within the Newaukum River basin that benefit all Chinook stocks. However, ongoing challenges related to climate change and habitat degradation must be addressed to ensure the long-term sustainability of salmon and steelhead populations. Continued investment in habitat restoration, hatchery management, and collaborative conservation efforts will be vital for future success.