DESCRIPTION
This study will identify life-stage-specific survival rates for wild-origin juvenile spring Chinook salmon and summer steelhead in the Tucannon River, which in turn will help direct habitat restoration efforts based on survival and distribution of PIT tagged fish. The relative distribution of habitat use and associated survival rates within Tucannon River overwintering and migration habitats are currently unknown, but are critical uncertainties to recovery actions. This project will attempt to identify if, when, and where the population bottlenecks exist for spring Chinook and summer steelhead in the Tucannon River using juvenile survival and distribution data provided by the four instream PIT arrays, and offering an improved method for identifying limiting factors and prioritizing restoration actions that are currently implemented in the basin. In order to evaluate life-stage-specific survival, river segment-scale habitat use, and potential carrying capacity limitations for juvenile salmon and steelhead, we will implement spatially stratified electrofishing surveys to capture fish and mark them with passive integrated transponder (PIT) tags. Tagging efforts will occur during late September/early October throughout the mainstem Tucannon River using a spatially balanced design. Subsequent detections of tagged juveniles will inform CJS survival model.
Tucannon River spring Chinook salmon and summer steelhead are currently protected under the US Endangered Species Act and empirical estimates of juvenile survival and movement are needed to develop and evaluate within basin habitat restoration actions. To address this need we continued and expanded upon a project conducted in 2013 and 2014. We captured parr in October 2016 and 2017 in three strata upstream of rkm 17.8, tagged parr with Passive Integrated Transponder (PIT) tags, and detected the released PIT tagged fish at detection sites during their seaward emigration from the Tucannon, Snake, and Columbia rivers. In addition, we performed limited winter mobile detection surveys to assess winter habitat utilization. We used a control-treatment design to estimate the overwinter survival of fall parr in the Tucannon River by comparison of the relative survival of the parr to smolts PIT tagged at rkm 3 during the spring outmigration using a Bayesian Cormack-Jolly-Seber model. Overwinter survival estimates for two tagging strata over two years ranged from 17.8% to 30.2% for spring Chinook salmon and 7.7% to 42.1% for summer steelhead parr depending on tagging strata, age and year. Detections at four Instream PIT Tag Detection sites (IPTDS) in the Tucannon basin allowed us to estimate overwinter reach scale survival by tagging strata and to identify important reaches for overwintering in the upper and middle basin and migration in the middle and lower basin. Although overwinter survival estimates for spring Chinook salmon were similar between the two tagging strata within the same year, we observed differences in the spatial/temporal movement patterns based on tagging site between years that was related to different winter flow and thermal regimes. The survival estimates and movement patterns from this tagging and detection study allowed us to better understand the winter ecology of spring Chinook parr in this watershed and develop habitat restoration recommendations to improve overwinter habitat for this at risk population.
Tucannon River Population
