Identifying Suitable Habitat for Chinook Salmon across a Large, Glaciated Watershed

Abstract

Ecosystem management requires information on habitat suitability across broad scales; however, comprehensive environmental surveys in remote areas are often impractical and expensive to carry out. Intrinsic Potential (IP) models provide a means to identify on a broad scale those portions of the landscape that can provide essential habitat for various freshwater fish species. These models are derived from watershed patterns and processes that are persistent and not readily affected by human activities. We developed an IP model for rearing habitat of Chinook Salmon throughout the Copper River watershed (63,000 km²) in southcentral Alaska, utilizing digital elevation models, expert opinion, and field surveys. Our model uses three variables—mean annual flow, gradient, and glacial influence—and adequately predicts where probable habitat for juvenile Chinook Salmon occurs across this large landscape. This model can help resource managers map critical habitat for salmon throughout the Copper River watershed, direct field research to appropriate stream reaches, and assist managers in prioritizing restoration actions, such as culvert replacement. Intrinsic Potential modeling is broadly applicable to other salmonid species and geographies and may inform future work on the ecological impacts of climate change in polar and subpolar river systems.

Received August 23, 2013; accepted December 20, 2013

ACKNOWLEDGMENTS

This work was supported by funding from the Gordon and Betty Moore Foundation. We thank the Alaska Department of Fish and Game and the Native Village of Eyak for field assistance and survey data. Thanks also to E. Veach and M. McCormick, Wrangell St. Elias National Park and Preserve, for National Park Service survey data. This work would not have been possible without our many field assistants, particularly B. Hansen, J. Fisher, and C. Somerville. M. Goslin, A. Fenix, and N. Lyman helped with model building and GIS analysis. We also thank M. Somerville for help with field logistics and R. Brenner for assistance with the figures. C. Sergeant and two anonymous reviewers provided helpful comments on the manuscript.