In this report we examine historical Pacific climate and Northeast
Pacific salmon catch and population data. Of particular interest to this study is the role
that climate fluctuations may play in the extinctions of isolated breeding populations
of Pacific salmon.
We discuss the results from two distinct types of analysis. In the first type we
adopt a Pacific basin scale perspective and search for linear relationships between climate
and salmon metapopulation variability along the Pacific coast from Alaska to California.
This approach yields a robust large scale pattern of salmon metapopulation responses to
a recurring pattern of interdecadal climate variability we are calling the Pacific Interdecadal
Oscillation (PDO). In the Pacific the positive phase of the PDO has prevailed since 1977
and the associated environmental conditions have favored high salmon productivity in
Alaska and low productivity for many salmon metapopulations in southern British
Columbia, the Pacific Northwest, and California. In the second approach we select
a few case studies that illustrate
complex, nonlinear relationships between climate and salmon population variability. The
case studies highlight the sometimes surprising nature of salmon population
responses to a variety of simultaneous forcings that include climate fluctuations.
Climate alone is not likely to cause widespread extinctions
of Pacific salmon populations. Our work suggests that,
in order for climate variability to effect
widespread risks of extinction, climate forcing probably needs to be
superimposed upon salmonid ecosystems under extreme stress from humans.
For an HTML version of the text (sorry, no figures yet) of this report, click here.
An 850 kB UNIX-style compressed tar file including all the Postscript files for the paper is here.
Links to related articles:
A Pacific Interdecadal Climate Oscillation with Impacts on Salmon Production
Inverse production regimes: Alaskan and West Coast Pacific Salmon
email:
mantua@atmos.washington.edu