Habitat suitability and availability for rainbow trout Oncorhynchus mykiss in the Canyon Reservoir tailrace Greg Cummings

Habitat Study Objectives Develop hydraulic models by integrating river features Assess changes in rainbow trout habitat suitability and availability with flow Provide recommendations for flow and habitat restoration

Study Area 10.5 miles below dam Extensive pool habitat (75%) Dominant substrate is bedrock (61%) 3 study sections Each approx. 1 mile long

Methods Physical Habitat Simulation System (PHABSIM) – Process to evaluate the effects of flow manipulation on riverine habitats – Based on habitat suitability criteria (HSC) for rainbow trout – Hydraulic modeling used to assess habitat quality and quantity at various flows

Methods Habitat Suitability Criteria – Literature sources and field collection – Collected for spawning, juvenile, and adult rainbow trout – Depth, velocity, and substrate

Methods Habitat Mapping – Traditional surveying – Bathymetric surveying – Side scan sonar – LIDAR (Light Detection and Ranging) – Aerial photography – GIS

Methods Hydraulic modeling – Topography, substrate, water surface elevations – Depth and velocity modeled at chosen discharge rates – Based on flow agreements, permits, and model construction Flow Rate (cfs)Flow Rate (cms)

Results HSC for telemetry study

Results HSC envelope curves for depth

Results HSC envelope curves for velocity

Results HSC envelope curves for substrate

Results Overall Habitat Quantity and Quality (Adults)

Results Overall optimal habitat

Results Adult Trout Habitat/Flow Statistics Discharge (cms) Discharge (cfs)WUA (m 2 ) % Max WUA Optimal Habitat (m 2 ) % of study area

Discussion Adult trout habitat – Current flow agreement provides 90% maximum WUA and 80% optimal habitat in the study area – Habitat not likely the main limiting factor for survival although some improvements can be made – Most areas that were unsuitable for adult trout at low flows (<80 cfs) were due to insufficient depth (<0.2m)

Discussion Temperature – Likely main limiting factor for adult trout survival – From the dam to WWS, temperatures rarely exceed tolerance limits – At Ponderosa Crossing temperatures sometimes exceed tolerance limits – Beyond 3 rd Crossing temperatures frequently exceed tolerance limits Dam WWS Ponderosa 3 rd Crossing

Discussion Flow agreement limitations – Reliance on Canyon Reservoir water level – Intermittent nature of prescribed flows ̶Even with prescribed flows water temperatures beyond Ponderosa Crossing exceed tolerance limits

Flow Recommendations Discharge rate of 140 cfs could be considered a minimum threshold for habitat 20 cfs could be considered a critical minimum flow rate during drought 470 cfs would maximize optimal habitat. However, unlikely to be maintained and can prevent wading Discharges higher than 470 cfs reduce optimal habitat due to unsuitable velocities for adult trout

Habitat Enhancement Proper assessment, planning, and preparation Instream cover and structures to increase depth could improve habitat suitability

Habitat Enhancement Riparian enhancement could stabilize streambanks, while increasing shading, nutrients, macroinvertebrate habitat, and overhead cover for fish

Habitat Enhancement Monitoring and maintenance Cooperation with landowners and river authorities Consultation with stream restoration experts and other cooperators

Thesis Committee Thomas B. Hardy, Ph.D. – Chief Science Officer, Meadows Center for Water and the Environment – Department of Biology, Texas State University Adam J. Kaeser, Ph.D. – Aquatic Ecologist, U.S. Fish and Wildlife Service Timothy H. Bonner, Ph.D. – Department of Biology, Texas State University

Acknowledgements