Annual Report: Trinity River Basin Salmon and Steelhead Monitoring Project: Chinook and Coho Salmon and Fall-Run Steelhead Run-Size Estimates Using Mark-Recapture Methods 2014-2015 Season

The California Department of Fish and Wildlife's Trinity River Project conducted tagging and recapture operations from June 2014 through March 2015 to produce run-size, angler harvest, and spawner escapement estimates of spring-run (spring Chinook) and fall-run Chinook salmon [fall Chinook (Oncorhynchus tshawytscha)], coho salmon (O.kisutch), and fall steelhead (O. mykiss) in the Trinity River basin. The monitoring results
informs the Trinity River Restoration Program’s (TRRP) adaptive management decision making process and helps to evaluate progress toward achieving fundamental objectives outlined in the Integrated Assessment Plan (TRRP, 2009). Utilizing a Petersen mark-recapture methodology, we estimate a run-size of 6,959 (95% CI 6,419 – 7,523) spring Chinook migrated into the Trinity River basin upstream of Junction City weir. The run was comprised of an estimated 1,998 naturally-produced adults and 132 naturally-produced jacks and 4,300 hatchery-produced adults and 528 hatchery-produced jacks. Using tags returned by anglers we estimate 227 spring
Chinook were harvested, yielding an escapement of 6,732 fish. The escapement of 1,931 naturally-produced adult spring Chinook was 32.2% of the TRRP goal of 6,000 spring Chinook. An estimated run-size of 37,829 (95% CI 33,056 – 43,670) fall Chinook migrated past Willow Creek weir (WCW). The run was comprised of an estimated 11,017 naturally produced adults and 6,332 naturally-produced jack salmon and 19,874 hatchery produced adults and 606 hatchery-produced jacks. We estimate 926 were harvested by anglers, yielding a total escapement of 36,803 fish. The escapement of 10,700 naturally-produced adult fall Chinook was 17.4% of the 62,000 fish TRRP goal. Both the coho run-size and escapement in the Trinity above Willow Creek were estimated at 13,537 (95% CI 12,133 – 15,021), because no coho were reported as harvested.