To What Degree is This Water an Issue? Using Environmental DNA to Assess a Thermal Passage Barrier on the Tualatin River
Start Date
3-17-2025 2:20 PM
End Date
3-17-2025 2:29 PM
Abstract
Clean Water Services (CWS), a special-use district, helps jointly manage and maintain flow and water quality in the Tualatin River in part through discharges into the river from four water resource and recovery facilities (WRRFs). While water inputs from WRRFs are critical to flow management of the Tualatin River, treated water is warm in nature, leading to on-going questions on whether water temperatures downstream of treated water inputs block Coho migration. To address this, we designed a multiyear environmental DNA study with the goals of better understanding Coho migration timing, environmental cues, and the potential for thermal discharge to prevent upstream migration. First, a time series was constructed from water samples collected at regular intervals from July 2023 - June 2024. We found Coho DNA concentration was low year-round, increasing from September – January, which correlates with timing of migration and spawning activity. Additionally, we found increases in DNA concentration lagged Willamette Falls fish counts by roughly a week, and positive DNA detections began only after river temperature fell below 20°C. Using this information, two sites were sampled concurrently from August 2024 - February 2025 to determine whether DNA concentration differed upstream versus downstream of thermal inputs. Initial results show similar DNA concentrations at both sites and confirm the lag time between fish counts and presence of Coho in the Tualatin River. This study provides novel insight into Coho migration in the Tualatin River, helping better plan for future climate scenarios.
Subjects
Animal ecology, Conservation biology, Fisheries, Water quality
Persistent Identifier
https://archives.pdx.edu/ds/psu/43082
Creative Commons License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License.
To What Degree is This Water an Issue? Using Environmental DNA to Assess a Thermal Passage Barrier on the Tualatin River
Clean Water Services (CWS), a special-use district, helps jointly manage and maintain flow and water quality in the Tualatin River in part through discharges into the river from four water resource and recovery facilities (WRRFs). While water inputs from WRRFs are critical to flow management of the Tualatin River, treated water is warm in nature, leading to on-going questions on whether water temperatures downstream of treated water inputs block Coho migration. To address this, we designed a multiyear environmental DNA study with the goals of better understanding Coho migration timing, environmental cues, and the potential for thermal discharge to prevent upstream migration. First, a time series was constructed from water samples collected at regular intervals from July 2023 - June 2024. We found Coho DNA concentration was low year-round, increasing from September – January, which correlates with timing of migration and spawning activity. Additionally, we found increases in DNA concentration lagged Willamette Falls fish counts by roughly a week, and positive DNA detections began only after river temperature fell below 20°C. Using this information, two sites were sampled concurrently from August 2024 - February 2025 to determine whether DNA concentration differed upstream versus downstream of thermal inputs. Initial results show similar DNA concentrations at both sites and confirm the lag time between fish counts and presence of Coho in the Tualatin River. This study provides novel insight into Coho migration in the Tualatin River, helping better plan for future climate scenarios.
