The change in water circulation and its implication for the distribution and abundance of salmon in the western Bering Sea in the early 21st century

Abstract

A “change” in water circulation took place in the Bering Sea in 2007. The Bering Sea cyclonic gyre decreased to the size of the Commander Basin; the longitudinal northward flow from the Near Strait intensified, and the latitudinal westward flow from the Aleutian Basin along the Koryak coast and the Bering Slope Current became noticeably weaker. The longitudinal flow formed a hydrodynamic front along the border of the Russian EEZ that prevented cold subsurface waters from spreading eastward. The changes in circulation of waters that were observed in the Bering Sea during the 2007–2011 period, as compared to the situation in 2002–2006, had an influence on the intensity of feeding migrations of immature salmon into Russian waters. The abundance of immature chum, sockeye, and chinook salmon in the western part of the sea declined and the pattern of their spatial distribution was altered. In 2012, after the water circulation changed to its original pattern, the abundance of salmon was restored to the levels that were recorded in 2002–2006.