DOI: 10.5061/dryad.2280gb63k
title: Long-term biennial patterns in Puget Sound Chinook salmon and Southern Resident killer whales: the role of pink salmon and implications for ecosystem management

description: Pink salmon returning from the Pacific Ocean have reached record-high
 abundances, leading to adverse effects on numerous marine species,
 including Chinook salmon. In Puget Sound, Washington, odd-year abundances
 of pink salmon spawners tripled after 1997; few return in even years. We
 used this extreme biennial pattern to search for corresponding patterns in
 natural-origin Chinook abundance and productivity that might also explain
 biennial mortality and births in Chinook-dependent Southern Resident
 killer whales (SRKW) that emerged during their decline after the 1997/1998
 El Niño. In the Sultan River, Chinook spawners shifted upstream in
 odd-numbered years when sympatric pink salmon were abundant in the lower
 river and Chinook fry per redd declined. Since 1997, Puget Sound Chinook
 abundance averaged 34% less in odd- versus even-years, and was negatively
 correlated with pink abundance. These findings support the hypothesis that
 pink salmon reduced Chinook abundance and influenced the biennial patterns
 and decline of SRKW. Management actions to reduce the growing abundance of
 pink salmon, especially those reaching spawning grounds, could potentially
 benefit the recovery of ESA-listed Chinook salmon and SRKWs.
description: <strong>Sultan River Data</strong>
 The Snohomish County PUD conducted spawning ground surveys to
 estimate spawning abundances of Chinook and pink salmon by river reach of
 each year, 1991-2022, using protocols developed by the Washington
 Department of Fish and Wildlife and Indian Tribes for rivers throughout
 the state (Smith and Castle 1994). Prior to 1991, only total river salmon
 counts were available.  Juvenile Chinook salmon emigrating from the Sultan
 River (primarily age 0) were enumerated using the protocol described by
 Murdock (2000) and Snohomish County PUD (2011).
 Murdoch, A., Petersen, K., Miller, T., Tonseth, M., and Randolph,
 T. 2000. Freshwater production and emigration of juvenile spring chinook
 from the Chiwawa River in 1999. Prepared for: Public Utility District
 Number 1 of Chelan County. Wenatchee, WA. Smith, C.,
 and Castle, P. 1994. Puget Sound Chinook salmon (<em>Oncorhynchus
 tshawytscha</em>) escapement estimates and methods - 1991. Northwest
 Fishery Resource Bulletin Project Report Series No. 1. Washington
 Department of Fish and Wildlife, Olympia Washington.
 Snohomish County PUD. 2011. Fisheries and habitat monitoring
 plan, Henry M. Jackson Hydroelectric Project with appendices. Everett,
 WA. <strong>Puget Sound Chinook salmon
 data</strong> Puget Sound escapements (spawners)
 and terminal runs (fish entering Puget Sound) of Pacific Salmon Commission
 Chinook Technical Committee wild Chinook salmon escapement indicator
 stocks.  Blank cells indicate no data available. The reported 1997 run for
 the Stillaguamish River (17,298 fish) was an extreme outlier and excluded
 from the analysis. Data source:  Table B7 of PSC  2023.
 Pacific Salmon Commission Joint Chinook Technical Committee Report. Annual
 report of catch and escapement for 2022. Report TCChinook (23)-02. Annual
 values prior to 2009 were taken from the 2019 report. Available at www.psc.org.  
 <strong>Puget Sound pink salmon
 data</strong> Pink salmon escapement and runs to
 Puget Sound indicator watersheds and to all Puget Sound
 watersheds. Primary data source: PFMC. 2023.
 Escapements to inland fisheries and spawning areas. Salmon review Appendix
 B. Pacific Fishery Management Council. Available at www.pcouncil.org.
 Escapement to the Green River provided by E Warner, Muckleshoot Indian
 Tribe. Prior to 1999, nearly zero pink salmon returned to the Green River.
 Blank cells indicate few if any pink salmon are present. Even year pink
 salmon values for the Snohomish watershed are from
 https://fortress.wa.gov/dfw/score/score/species/species.jsp
description: # Long-term biennial patterns in Puget Sound Chinook salmon and Southern
 Resident killer whales: the role of pink salmon and implications for
 ecosystem management
 [https://doi.org/10.5061/dryad.2280gb63k](https://doi.org/10.5061/dryad.2280gb63k) ## Description of the data and file structure SalmonCSVfiles ### Files and variables #### File: Sultan\_River\_salmon.csv **Description:** The Snohomish County PUD conducted spawning ground surveys to estimate spawning abundances of Chinook and pink salmon by river reach of each year, 1991-2022, using protocols developed by the Washington Department of Fish and Wildlife and Indian Tribes for rivers throughout the state (Smith and Castle 1994). Prior to 1991, only total river salmon counts were available. Juvenile Chinook salmon emigrating from the Sultan River (primarily age 0) were enumerated using the protocol described by Murdock (2000) and Snohomish County PUD (2011). ##### Variables | Spawn\_year | | :---------------------------------------------------------------------------------------------------------------------- | | Chinook\_spawners\_all\_areas. Total number of Chinook salmon spawning in the entire Sultan River each year. | | Chinook\_redds\_all\_areas. Total number of Chinook salmon redds (spawning nests) in the entire Sultan River each year. | | Proportion\_Chinook\_spawners\_lower\_river. Proportion of Chinook spawning in the lower4.6km of the Sultan River. | | Chinook\_fry\_per\_redd. Number of Chinook fry emigrating from the Sultan River per redd. | | Chinook\_fry. Total number of Chinook salmon fry emigrating from the Sultan River each year. | | Pink\_spawners. Total number of pink salmon spawning in the entire Sultan River each year. | #### File: Puget\_Sound\_Chinook\_salmon.csv **Description:** Puget Sound escapements (spawners) and terminal runs (fish entering Puget Sound) of Pacific Salmon Commission Chinook Technical Committee wild Chinook salmon escapement indicator stocks. The reported 1997 run for the Stillaguamish River (17,298 fish) was an extreme outlier and excluded from the analysis. ##### Variables | Year | | :--------------------------------------------------------------------------------------------- | | Nooksack\_Spring\_Spawners. Number of spring Chinook salmon spawning in the river. | | Skagit\_Spring\_Spawners. Number of spring Chinook salmon spawning in the river. | | Skagit\_Spring\_Run. Total abundance of spring Chinook salmon (catch+spawners). | | Skagit\_R\_summer\_fall\_spawners. Number of summer-fall Chinook salmon spawning in the river. | | Skagit\_R\_summer\_fall\_run. Total abundance of summer-fall Chinook salmon (catch+spawners). | | Stillaguamish\_Spawners. Number of summer-fall Chinook salmon spawning in the river. | | Stillaguamish\_Run. Total abundance of summer-fall Chinook salmon (catch+spawners). | | Snohomish\_Spawners. Number of summer-fall Chinook salmon spawning in the river. | | Snohomish\_Run. Total abundance of summer-fall Chinook salmon (catch+spawners). | | Green\_Spawners. Number of summer-fall Chinook salmon spawning in the river. | | Green\_Run. Total abundance of summer-fall Chinook salmon (catch+spawners). | | Lake\_Washington\_Spawners. Number of summer-fall Chinook salmon spawning in the river. | ### Files and variables #### File: Puget\_Sound\_Pink\_salmon.csv **Description:** Pink salmon escapement (spawners) and runs (catch and spawners) to Puget Sound indicator watersheds and to all Puget Sound watersheds. Primary data source: PFMC. 2023. Escapements to inland fisheries and spawning areas. Salmon review Appendix B. Pacific Fishery Management Council. Available at [www.pcouncil.org](http://www.pcouncil.org). Escapement to the Green River provided by E Warner, Muckleshoot Indian Tribe. Prior to 1999, nearly zero pink salmon returned to the Green River. Blank cells indicate few if any pink salmon are present. Even year pink salmon values for the Snohomish watershed are from [https://fortress.wa.gov/dfw/score/score/species/species.jsp](https://fortress.wa.gov/dfw/score/score/species/species.jsp) ##### Variables | Year | | :--------------------------------------------------------------------------------------------------------- | | Nooksack\_Spawners. Number of pink salmon spawning in the river. | | Nooksack\_Run. Total abundance of pink salmon (catch+spawners). | | Skagit\_Spawners. Number of pink salmon spawning in the river. | | Skagit\_Run. Total abundance of pink salmon (catch+spawners). | | Stillaguamish\_Snohomish\_Spawners. Number of pink salmon spawning in the river. | | Stillaguamish\_Snohomish\_Run. Total abundance of pink salmon (catch+spawners). | | Green\_Spawners. Number of pink salmon spawning in the river. | | Total\_Puget\_Sound\_Spawners. Number of pink salmon spawning in all Puget Sound rivers. | | Total\_Puget\_Sound\_Run. Total abundance of pink salmon returning to Puget Sound rivers (catch+spawners). |