THE OPTIMAL STABILITY WINDOW - A MECHANISM UNDERLYING DECADAL FLUCTUATIONS IN NORTH PACIFIC SALMON STOCKS

While recent evidence suggests that North Pacific salmon stocks are in fluenced by decadal variability in atmospheric forcing of the ocean, t he actual combination of physical and biological processes that determ ines this linkage has not been identified. This paper describes a poss ible scenario in which water column stability is the primary factor by which the physical environment influences phytoplankton production, t he basis for production at higher trophic levels. Variation in the str ength of the wintertime Aleutian Low pressure area affects water colum n stabilities, hence primary production, along the entire eastern boun dary of the North Pacific. The 'optimal stability window' explains the qualitative relationship between fish stocks and the strength of the winter Aleutian Low, as well as the observed out-of-phase variation be tween northern and southern salmon stocks.