CLBMON21: Mid-Columbia River Juvenile White Sturgeon Detection and Habitat Use Program 2007 to 2017 Synthesis Report

Author: Okanagan Nation Alliance

The purpose of CLBMON-21 was to determine the suitability of the MCR as a second recovery area for White Sturgeon in the Upper Columbia River Basin and the evaluate the potential for a self-sustaining or failsafe population (i.e., a second population supported by artificial supplementation of juvenile White Sturgeon to provide future broodstock or genetic biodiversity in the event of a catastrophic failure of the primary population). An 11-year monitoring program was developed to investigate juvenile survival, growth, movement, habitat use, and habitat availability to support building a self-sustaining population in this section of the Columbia River.

1. Where are the habitat locations utilized by juvenile Sturgeon in the Middle-Columbia?
Based on data collected using both acoustic telemetry and direct capture efforts, juvenile White Sturgeon exhibit highest use of habitats near Greenslide Cr. (RKm 212) downstream to Beaton Flats (Rkm 55) and, to a lesser extent, further south into Arrow Lakes Reservoir. Much of the habitat use observed has been within the river- reservoir interface zone around Beaton Flats and upstream towards Revelstoke. Juveniles have not been directly captured below the Beaton Flats area in large numbers but telemetry has identified a few individuals further downstream towards Nakusp.
2. What are the physical and hydraulic properties of this habitat that define its suitability as juvenile Sturgeon habitat?
Juvenile White Sturgeon use deep (>10 m), low velocity (<0.5 m/s) habitats with fine substrates (sand/silt/clay). This is based primarily on movements of acoustically tagged juveniles (n=250) and general locations of capture. When releases occurred at the City of Revelstoke (RKm 229, 2007-2012), juveniles were found to move quickly downstream to Mulvehill and Greenslide Creeks, and Akolkolex River areas and further downstream into the reservoir where conditions are more favorable. Accordingly, the release site was moved to Shelter Bay (RKm 177) in 2013 to ensure release in closer proximity to suitable habitats. 3. What is the quantity of available habitat meeting these conditions in the Middle-Columbia? The amount of available preferred habitat for juvenile White Sturgeon is related to the ALR water elevation which is influenced by discharge from REV. Recruitment does not appear to be limited by juvenile habitat quality and quantity; however, this hypothesis cannot be rejected at this time. Relative weights of juveniles captured in the MCR are near expected for their size, indicating that the surviving fish are growing at near normal rates. This finding does not support a hypothesis that food resources in the MCR are limiting juvenile survival and growth. 4. How do hydraulic conditions resulting from dam and reservoir operations relate to habitat suitability for juvenile White Sturgeon in the Middle-Columbia? Both REV discharges and Arrow Lakes Reservoir operations influence habitat quality and quantity. Discharge from REV influences the quality and quantity of habitat in riverine sections; however the effects diminish with downstream distance. Higher reservoir elevations backwatering the river section result in greater availability of deeper, lower velocity habitats further upstream. The ALR levels affect Sturgeon movements in the river section and attenuate the effects of varying dam discharges on Sturgeon habitat. 5. What are the survival rates of juvenile White Sturgeon in the Middle-Columbia River? Survival has not been estimated due to low recapture rates, which are attributed to a large study area and low capture efficiency. On average for all recaptured fish, total annual growth was 11.9 cm/year in length and 210 g/year in weight. This is comparable the juveniles released and recaptured in the Lower Columbia River juvenile sturgeon program. While most fish in the MCR have been captured in the same year they were released, one of the captured juveniles had survived to age-10. Additional capture data are required to adequately address the survival question. 6. Can modifications be made to the operations of Revelstoke Dam and/or Arrow Lakes Reservoir to protect or enhance juvenile White Sturgeon habitat? The main areas of habitat use by juvenile Sturgeon are situated >25 km downstream from REV, where it is unlikely that significant dam operational improvements can be made. Detecting a response to operational modifications from REV would also be difficult as many juvenile White Sturgeon move quickly downstream to RKm 200 205 following release. At this distance from the dam, large changes in flows are ameliorated and backwatering from the reservoir likely changes the flow dynamics. The landforms around the preferred area of the Walter Hardman Generation Station and Akolkolex River (Rkm 200) constrict the Columbia River, which may be creating conditions that are more suitable to juvenile rearing for at least some of the year.
For the reservoir, maintaining the ALR water elevation at levels that ensure a deep thalweg (425-430 MASL) around Greenslide Creek (RKm 212) will maximize the amount of preferred habitat that is currently being used by juveniles in this area.

1. Where are the habitat locations utilized by juvenile Sturgeon in the Middle-Columbia?
Based on data collected using both acoustic telemetry and direct capture efforts, juvenile White Sturgeon exhibit highest use of habitats near Greenslide Cr. (RKm 212) downstream to Beaton Flats (Rkm 55) and, to a lesser extent, further south into Arrow Lakes Reservoir. Much of the habitat use observed has been within the river- reservoir interface zone around Beaton Flats and upstream towards Revelstoke. Juveniles have not been directly captured below the Beaton Flats area in large numbers but telemetry has identified a few individuals further downstream towards Nakusp.
2. What are the physical and hydraulic properties of this habitat that define its suitability as juvenile Sturgeon habitat?
Juvenile White Sturgeon use deep (>10 m), low velocity (<0.5 m/s) habitats with fine substrates (sand/silt/clay). This is based primarily on movements of acoustically tagged juveniles (n=250) and general locations of capture. When releases occurred at the City of Revelstoke (RKm 229, 2007-2012), juveniles were found to move quickly downstream to Mulvehill and Greenslide Creeks, and Akolkolex River areas and further downstream into the reservoir where conditions are more favorable. Accordingly, the release site was moved to Shelter Bay (RKm 177) in 2013 to ensure release in closer proximity to suitable habitats. 3. What is the quantity of available habitat meeting these conditions in the Middle-Columbia? The amount of available preferred habitat for juvenile White Sturgeon is related to the ALR water elevation which is influenced by discharge from REV. Recruitment does not appear to be limited by juvenile habitat quality and quantity; however, this hypothesis cannot be rejected at this time. Relative weights of juveniles captured in the MCR are near expected for their size, indicating that the surviving fish are growing at near normal rates. This finding does not support a hypothesis that food resources in the MCR are limiting juvenile survival and growth. 4. How do hydraulic conditions resulting from dam and reservoir operations relate to habitat suitability for juvenile White Sturgeon in the Middle-Columbia? Both REV discharges and Arrow Lakes Reservoir operations influence habitat quality and quantity. Discharge from REV influences the quality and quantity of habitat in riverine sections; however the effects diminish with downstream distance. Higher reservoir elevations backwatering the river section result in greater availability of deeper, lower velocity habitats further upstream. The ALR levels affect Sturgeon movements in the river section and attenuate the effects of varying dam discharges on Sturgeon habitat. 5. What are the survival rates of juvenile White Sturgeon in the Middle-Columbia River? Survival has not been estimated due to low recapture rates, which are attributed to a large study area and low capture efficiency. On average for all recaptured fish, total annual growth was 11.9 cm/year in length and 210 g/year in weight. This is comparable the juveniles released and recaptured in the Lower Columbia River juvenile sturgeon program. While most fish in the MCR have been captured in the same year they were released, one of the captured juveniles had survived to age-10. Additional capture data are required to adequately address the survival question. 6. Can modifications be made to the operations of Revelstoke Dam and/or Arrow Lakes Reservoir to protect or enhance juvenile White Sturgeon habitat? The main areas of habitat use by juvenile Sturgeon are situated >25 km downstream from REV, where it is unlikely that significant dam operational improvements can be made. Detecting a response to operational modifications from REV would also be difficult as many juvenile White Sturgeon move quickly downstream to RKm 200 205 following release. At this distance from the dam, large changes in flows are ameliorated and backwatering from the reservoir likely changes the flow dynamics. The landforms around the preferred area of the Walter Hardman Generation Station and Akolkolex River (Rkm 200) constrict the Columbia River, which may be creating conditions that are more suitable to juvenile rearing for at least some of the year.
For the reservoir, maintaining the ALR water elevation at levels that ensure a deep thalweg (425-430 MASL) around Greenslide Creek (RKm 212) will maximize the amount of preferred habitat that is currently being used by juveniles in this area.