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

Abstract

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.

Weakened portfolio effects constrain management effectiveness for population aggregates

“…While reduced productivity (Peterman and Dorner , Dorner et al. ), increased variability (Satterthwaite and Carlson ), and increased synchrony (Kilduff et al. , Satterthwaite and Carlson , Freshwater et al.…”

Adaptive Management and Climate Change Adaptation: Two Mutually Beneficial Areas of Practice

“…All five basins are experiencing impacts of climate change at a scale much greater than the scale at which managers have authority (Challenge 3). For the three salmon‐bearing basins (Russian, Trinity, Okanagan), recent coast‐wide declines in both Chinook and sockeye salmon production appear to be most strongly related to large‐scale changes in ocean conditions driven by climate change, rather than by local habitat factors (Marmorek et al ; Peterman and Dorner ; Dorner et al ). In the Trinity Basin, further revisions to water allocations (e.g., increasing the amount of water allocated to the Trinity River in Table ) would require negotiations outside of the Trinity Basin and the authority of the TRRP (e.g., with water users in the Central Valley, who use water diverted from the Trinity Basin into the Sacramento Basin); this is very unlikely to occur.…”

Impact of time-varying productivity on estimated stock–recruitment parameters and biological reference points

“…Our model focused on temporal trends in productivity and exploitation that have occurred for Fraser River sockeye salmon, though these trends have also been found across other stocks and salmon species, and so results may be more broadly applicable (Peterman and Dorner 2012;Malick and Cox 2016;Dorner et al 2018). While our analyses focused on only two benchmarks commonly used to assess status of Pacific salmon, the closed-loop simulation approach could be readily adapted to accommodate other benchmarks, as well as other productivity trends and exploitation histories.…”