Spatial and temporal patterns of covariation in productivity of Chinook salmon populations of the northeastern Pacific Ocean

We expand on previous analyses of environmental factors related to productivity of Chinook salmon (Oncorhynchus tshawytscha) populations by analysing data on adult recruits per spawner from 24 wild (not hatchery) Chinook salmon stocks from Oregon through western Alaska. To determine the degree to which changes in productivity are shared and to help identify environmental variables that might be related to those changes, we estimated the magnitude and spatial characteristics of positive correlations in productivity trends among stocks separated by various distances. We used dynamic factor analysis to characterize shared time trends in productivity and found that these trends were most closely associated with the North Pacific Gyre Oscillation and, to a lesser extent, with the location of the bifurcation in the North Pacific Current as it reaches North America’s west coast. Chinook productivity patterns of separate populations have also become more synchronous in recent years, similar to results reported for other species of Pacific salmon. Such recent changes may reduce the resilience of the species to effects of climate change and habitat modification.