Trends in coho marine survival in relation to the regime concept

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Abstract

The marine survival of coho in the Strait of Georgia, Puget Sound, and off the coasts of Oregon decreased abruptly after the pattern of the Aleutian Low changed in 1989. This large scale, synchronous change indicates that trends in coho marine survivals were linked over the southern area of their distribution in the northeast Pacific and that these linkages were associated with a common event. The pattern of April flows from the Fraser River also changed abruptly about the same time as the changes that occurred in the Aleutian Low and was used as an indicator of regional climate change. These large scale, persistent trends in a biological or physical time series that shift quickly from one state to another can be considered to be regimes. The persistence and synchrony inherent in the regime concept can be used to conclude that the current trends of low coho marine survival may not change as long as April flows remain high.