Spatial and Temporal Patterns in Oxygen and Temperature in the Redwillow Watershed, 2022–2023
Final Report
Author(s)
Scott Seward, B.A., M.Sc.
Lindsay Marley, B.Sc., P.Biol.
Summary
Arctic grayling (Thymallus arcticus) were historically abundant in the Redwillow Hydrologic Unit Code (HUC) 6 watershed but have been extirpated from the Beaverlodge River HUC 8 watershed sub-basin since the mid-1990s and are thought to be in decline in the Redwillow River HUC 8 watershed sub-basin as well. Alberta Conservation Association (ACA) has been working in the Beaverlodge River watershed since 2004 to improve riparian health and water quality with the hope of bringing Arctic grayling back to the watershed. In this study, we assessed the spatial and temporal distribution of summer (August) water temperature and winter dissolved oxygen (DO), two key limiting factors for suitable Arctic grayling habitat, throughout the Beaverlodge River and Redwillow River watersheds to allow for comparison between the two watersheds and to help determine the suitability of the Beaverlodge River watershed to support Arctic grayling reintroduction.
In 2022–2023, we installed 61 temperature and 11 DO loggers throughout the Redwillow and Beaverlodge HUC 8 watershed sub-basins. Data integrity was maintained at 35 temperature and 10 DO sites, but compromised at the remaining sites due to large reductions in water levels and dry stream beds. Mean summer water temperature in 2022 in the Beaverlodge River watershed was categorized by thermal tolerance for Arctic grayling and was Optimal (7.5–17.0°C) at 17 sites, but in the Avoidance category (17.1–20.0°C) at ten sites and Stressed category (20.1–25.0°C) at two sites. Mean summer water temperature in the Redwillow River watershed was Optimal for Arctic grayling at two sites, but in the Avoidance category at three sites and Stressed category at one site. Mean winter DO concentrations in the Beaverlodge River watershed (n = 7) and Redwillow River watershed (n = 3) were above acute stress threshold for salmonids (>3.5 mg/L) at two sites each. Stream temperature and DO increased downstream (lower elevation) and were higher in mainstem creeks and rivers. Based on DO logger results in 2022–2023, portions of the Beaverlodge and Redwillow rivers were suitable overwintering habitat for Arctic grayling, but not the tributaries. However, dry sections in the Beaverlodge River watershed may impede fish passage between summer thermal refuge and overwintering habitat. Water temperature, overwintering DO concentrations, and water quantity may be limiting Arctic grayling recovery in the Beaverlodge River HUC 8 watershed.