Feist, B., E. Steel, D. Jensen and D. Sather.  2010. Does the Scale of our Observational Window Affect our Conclusions about Correlations Between Endangered Salmon Populations and Their Habitat? Landscape Ecology 25: 727-743.

Scale can affect the strength of apparent relationships between animals and habitat conditions.  In stream ecosystems, impacts on habitat in one reach of a stream might be the result of conditions in a different part of the watershed.  The importance of scale is especially true for anadromous salmon whose life cycle covers broad geographic areas.  To analyze the influence of scale on salmon habitat studies, authors examined relationships between Pacific salmon (Oncorhynchus spp.) and landscape data from GIS for three spatial scales:  local (stream reach), intermediate and basin-wide. Authors found that correlation between landscape condition and salmon response is influenced by scale.  Results however, suggest that there is no ideal scale for which to examine the significance of habitat attributes.  Authors therefore recommend that river restoration projects should consider landscape conditions at multiple scales. Reach, riparian area and greater basin land use/land cover, all impact salmon use of a site.  To maximize return on restoration projects, resource managers can use GIS to examine the influence of each of these 3 scales on salmon habitat use.

Fig. 2 Box and whisker plots comparing AIC for various fixed- and mixed-extent models as a function of extent, by subbasin and species (steelhead and Chinook)