PARENT SESSION
Oral Session - Quantitative Relationships Between Landscape Processes and Patterns and Wildlife - Morning Session Chair(s): Robinson, Vincent¹, ¹ University of Toronto at Mississauga, Mississauga, ON, Canada
Friday, April 2, 2004 9:00 AM - 11:00 AM Apollo Room 1-2

Does sufficient habitat remain to support viable chinook salmon populations in the Pacific Northwest of the United States? A spatially explicit assessment of spawning habitat in Puget Sound. ^*SANDERSON, BETH L. , DAVIES, JEREMY , LAGUEUX, KERRY , BEECHIE, TIM and RUCKELSHAUS, MARY , ¹ Northwest Fisheries Science Center,, Seattle, WA, USA

ABSTRACT- The present-day ability of freshwater habitat to support and sustain healthy populations of salmon is markedly different from historical conditions in the Pacific Northwest of the United States. In Puget Sound, where chinook salmon (Oncorhynchus tshawytscha) are listed as threatened under the ESA, we have developed methods for quantifying landscape-scale changes in available habitats used by adult and juvenile life stages. Our approach for deriving coarse-scale estimates of existing and historical chinook spawning habitat utilizes geospatial data coupled with empirical data from previous studies to develop a spawning suitability index for individual stream reaches. This index is derived using stream gradient, estimated bank full width, and riparian condition. Our results indicate that anthropogenic barriers exclude adult chinook from large areas of formerly accessible potential spawning habitat, and that changes in riparian condition have reduced the spawning potential of many reaches. As a result, the potential capacity for chinook spawners has declined by 40% on average for the 20+ populations in the basin. Land use of areas adjacent to potential spawning sites varies considerably among these populations indicating that a range of strategies will be needed in recovery planning. The validity of our approach is being assessed with field data and information from ongoing fine-scale analyses and local watershed groups. Ultimately our results will be used to identify large-scale patterns of habitat loss, compare the current versus historical potential of Puget Sound watersheds to support chinook salmon, and to assist local watershed groups in setting protection and restoration goals.

KEY WORDS: endangered species, stream network, chinook salmon, landscape model, habitat capacity