Historical population structure of Central Valley steelhead and its alteration by dams
Steven T. Lindley, National Oceanic and Atmospheric Administration
Robert S. Schick, National Oceanic and Atmospheric Administration
Aditya Agrawal, University of California, Santa Cruz
Matthew Goslin, University of California, Santa Cruz
Thomas E. Pearson, University of California, Santa Cruz
Ethan Mora, University of California, Santa Cruz
James J. Anderson, University of Washington
Bernard May, University of California, Davis
Sheila Greene, California Department of Water Resources
Charles Hanson, Hanson Environmental, Inc.
Alice Low, California Department of Fish and Game
Dennis McEwan, California Department of Fish and Game
R. Bruce MacFarlane, National Oceanic and Atmospheric Administration
Christina Swanson, The Bay Institute
John G. Williams, Independent Consultant

Download the Paper (PDF format) - February 2006 Related Files: Final_AppA_Lindley.pdf (48 kB) Appendix A: Estimating discharge from area and precipitation Figure01_Lindley.pdf (6374 kB) Figure 1 Figure02_Lindley.pdf (2162 kB) Figure 2 Figure04_Lindley.pdf (40 kB) Figure 4 Figure05_Lindley.pdf (1102 kB) Figure 5 Tell a colleague about it. Download Adobe Reader: Access to internal hyperlinks requires the full version of Adobe® Acrobat® 7.0. If you do not have this version, some internal hyperlinks may not work. This work has been peer reviewed.

ABSTRACT:
Effective conservation and recovery planning for Central Valley steelhead requires an understanding of historical population structure. We describe the historical structure of the Central Valley steelhead evolutionarily significant unit using a multi-phase modeling approach. In the first phase, we identify stream reaches possibly suitable for steelhead spawning and rearing using a habitat model based on environmental envelopes (stream discharge, gradient, and temperature) that takes a digital elevation model and climate data as inputs. We identified 151 patches of potentially suitable habitat with more than 10 km of stream habitat, with a total of 25,500 km of suitable habitat. We then measured the distances among habitat patches, and clustered together patches within 35 km of each other into 81 distinct habitat patches. Groups of fish using these 81 patches are hypothesized to be (or to have been) independent populations for recovery planning purposes. Consideration of climate and elevation differences among the 81 habitat areas suggests that there are at least four major subdivisions within the Central Valley steelhead ESU that correspond to geographic regions defined by the Sacramento River basin, Suisun Bay area tributaries, San Joaquin tributaries draining the Sierra Nevada, and lower-elevation streams draining to the Buena Vista and Tulare basins, upstream of the San Joaquin River. Of these, it appears that the Sacramento River basin was the main source of steelhead production. Presently, impassable dams block access to 80% of historically available habitat, and block access to all historical spawning habitat for about 38% of the historical populations of steelhead.