Cool tributary 26°C Subsurface inputs 25°C Coldwater refugia in high desert streams Thalweg 27°C

Water temperature 25°C Rainbow trout (Oncorhynchus mykiss)

Microhabitat coldwater refuge Adult chinook salmon (Oncorhynchus tshawytscha)

A bird’s-eye view of temperature

Airborne Thermal Remote Sensing Main channel Tributary confluence Ground-truth Middle Fork John Day River (Torgersen et al. 2001)

Reach-level associations (Torgersen et al. 1999)

Spatial heterogeneity in riverscapes (Fausch, Torgersen, Baxter, and Li 2002)

Habitat heterogeneity at two spatial scales Benthic sampling (1 m x 1 m). Larval Pacific lamprey (Torgersen and Close 2004)

Site selection and nested design

Distribution of larvae among sites Water depth (+) Shade (-)

Site 29 Rkm 9 n = 232 high density Spatial variation within sites NOT water depth Water velocity (-) % fines in substrate (+)

Scaling of fish assemblages and habitat relationships

Multivariate analysis of community structure Middle Fork John Day River WARM

Community structure in a COOL stream North Fork John Day River

Scale-dependent relationships Effects of spatial extent on ecological relationships Thermal crossover between warm- and coldwater species 20-22°CThermal crossover between warm- and coldwater species 20-22°C (Torgersen et al. 2006)

Review of concepts 1. Identifying the “correct” scale. Until we examine a range of scales, we are just guessing.

Review of concepts 2. Predictor variables change depending on scale of analysis. Collect data and develop models at more than one scale.

Review of concepts 3. Spatial extent is as important as resolution. Maintain flexibility across multiple scales (e.g., spatially continuous data).

Fausch, K. D., C. E. Torgersen, C. V. Baxter, and H. W. Li Landscapes to riverscapes: Bridging the gap between research and conservation of stream fishes. BioScience 52: Torgersen, C. E., D. M. Price, H. W. Li, and B. A. McIntosh Multiscale thermal refugia and stream habitat associations of chinook salmon in northeastern Oregon. Ecological Applications 9: Torgersen, C. E., R. N. Faux, B. A. McIntosh, N. J. Poage, and D. J. Norton Airborne thermal remote sensing for water temperature assessment in rivers and streams. Remote Sensing of Environment 76: Torgersen, C. E., and D. A. Close Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales. Freshwater Biology 49: Torgersen, C. E., C. V. Baxter, H. W. Li, and B. A. McIntosh Landscape influences on longitudinal patterns of river fishes: Spatially continuous analysis of fish-habitat relationships. Pages in R. M. Hughes, L. Wang, and P. W. Seelbach, editors. Landscape influences on stream habitats and biological assemblages. American Fisheries Society, Bethesda, Maryland.