2. “We sampled amphibians and classified microhabitat
in 35 to 50 2-m lengths of stream (sample units) in each drainage (total n 5 702; Fig. 1). We randomly selected five high-, five moderate-, and six low-intensity drainages for study ( ha).

3. Quantifying habitat associations at multiple scales
Benthic sampling (1 m x 1 m).
Larval Pacific lamprey
(Torgersen and Close 2004)

4. Site 41 rkm 33 medium density

5. Site selection and nested design

6. Distribution of lamprey larvae among sites
Water depth (+)
Shade (-)
(Torgersen and Close 2004)

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

8. Spatial scaling and measures of abundance
Spatial binning and smoothing
Measures of abundance (effective density)

9. Experimenting with bin size…
1 km

10. Spatial smoothing and binning
With binning and smoothing…
(Torgersen et al. 2008)

11. Spatial smoothing and binning

12. Experimenting with analysis “window”…
1 km

13. What is effective density and why is it important?
Standard population density **
Organisms/area sampled =
** Assumes that all habitats within the sampled area are suitable for the organism!

14. Scaling of abundance measures: Consequences of “binning”
Standard pop. density weighted by number of organisms
Effective density =

15. A simple example…
6 m
High density
10 m
Low density

16. Effective density and scale of sampling
Torgersen et al., unpushed data); Grant et al CJFAS.
Territory size and the measurement of salmonid abundance.
Scaling properties of the organism and its habitat

17. Grant, J. W. A. , S. O. Steingrimsson, E. R. Keeley, and R. A. Cunjak
Grant, J. W. A., S. O. Steingrimsson, E. R. Keeley, and R. A. Cunjak Implications of territory size for the measurement and prediction of salmonid abundance in streams. Canadian Journal of Fisheries and Aquatic Sciences 55 (Suppl. 1):
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., R. E. Gresswell, D. S. Bateman, and K. M. Burnett Spatial identification of tributary impacts in river networks Pages in S. P. Rice, A. G. Roy, and B. L. Rhoads, editors. River confluences, tributaries and the fluvial network. John Wiley & Sons Ltd., Chichester, UK.