25 Years of Juvenile Chinook Salmon Monitoring on the Mainstem Trinity River, California

Juvenile Chinook Salmon (Oncorhynchus tshawytscha) emigration from the mainstem Trinity River, California has been monitored since 1989 with rotary screw traps as a collaborative effort between the U.S. Fish and Wildlife Service, Hoopa Valley Tribal Fisheries Department, and Yurok Tribal Fisheries Program.  Annual data is collected at two sampling sites to: (1) evaluate the production of juvenile Chinook Salmon from the upper 65 kilometers of the mainstem Trinity River below Lewiston Dam, the primary restoration reach of the Trinity River Restoration Program (TRRP); and (2) provide data to enable evaluation of the production and emigration timing of juvenile Chinook Salmon through the lower Trinity River in response to managed flow regimes, thermal regimes, and restoration efforts.  This presentation focuses on the long term trends and patterns of juvenile Chinook Salmon abundance estimates using a Bayesian Time Stratified Spline routine developed by Carl Schwarz and Simon Bonner. The time series of abundance estimates are analyzed in the context of managed flow releases from Lewiston Dam, both before and after restoration flow regimes. Attempting to simulate a spring snow-melt hydrograph, these restoration flow regimes were fully implemented in 2005.