Rocky Mountain Research Station

Title: Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity

Author: Isaak, Daniel J.; Thurow, Russell F.; Rieman, Bruce E.; Dunham, Jason B.

Date: 2007

Source: Ecological Applications. 17(2): 352-364.

Description: Declines in many native fish populations have led to reassessments of management goals and shifted priorities from consumptive uses to species preservation. As management has shifted, relevant environmental characteristics have evolved from traditional metrics that described local habitat quality to characterizations of habitat size and connectivity. Despite the implications this shift has for how habitats may be prioritized for conservation, it has been rare to assess the relative importance of these habitat components. We used an information -- theoretic approach to select the best models from sets of logistic regressions that linked habitat quality, size, and connectivity to the occurrence of chinook salmon (Oncorhynchus tshawytscha) nests. Spawning distributions were censused annually from 1995 to 2004, and data were complemented with field measurements that described habitat quality in 43 suitable spawning patches across a stream network that drained 1150 km2 in central Idaho. Results indicated that the most plausible models were dominated by measures of habitat size and connectivity, whereas habitat quality was of minor importance. Connectivity was the strongest predictor of nest occurrence, but connectivity interacted with habitat size, which became relatively more important when populations were reduced. Comparison of observed nest distributions to null model predictions confirmed that the habitat size association was driven by a biological mechanism when populations were small, but this association may have been an area-related sampling artifact at higher abundances. The implications for habitat management are that the size and connectivity of existing habitat networks should be maintained whenever possible. In situations where habitat restoration is occurring, expansion of existing areas or creation of new habitats in key areas that increase connectivity may be beneficial. Information about habitat size and connectivity also could be used to strategically prioritize areas for improvement of local habitat quality, with areas not meeting minimum thresholds being deemed inappropriate for pursuit of restoration activities.

Keywords: chinook salmon, connectivity, habitat fragmentation, habitat geometry, metapopulation, nest, Oncorhynchus tshawytscha, patch, redd, sampling artifact

View and Print this Publication (205 K)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

Isaak, Daniel J.; Thurow, Russell F.; Rieman, Bruce E.; Dunham, Jason B.  2007.  Chinook salmon use of spawning patches: Relative roles of habitat quality, size, and connectivity.   Ecological Applications. 17(2): 352-364..