Research Document 1997/52

Marine environmental conditions in the Northwest Atlantic during 1996 potentially impacting Atlantic salmon (Salmo salar)

By K.F. Drinkwater, R. Pettipas, and L. Petrie

Abstract

Marine environmental conditions during 1996 in the Northwest Atlantic that could potentially impact eastern Canadian Atlantic salmon stocks are reviewed from available atmospheric and oceanographic datasets. The Labrador Sea is of particular interest because it is the overwintering site for most of these stocks. In the Labrador Sea, environmental conditions moderated during 1996 resulting in above normal air and ocean temperatures, the latter for the first time in over a decade. This warming is related to lower northwest winds over the region which in turn is linked to a weakening of the Icelandic Low air pressure system and a drop in the North Atlantic Oscillation (NAO). The NAO index, a measure of the strength of the large-scale atmospheric circulation, experienced its largest annual decrease in over 100 years of record. Based upon previous studies, these warmer winter conditions in the Labrador Sea should help to improve marine survival of salmon. Some of the inner Bay of Fundy salmon stocks are known to overwinter in the Gulf of Maine instead of migrating to the Labrador Sea. In the Gulf of Maine, temperatures are believed to be above normal as suggested by measurements at Boothbay Harbor, Maine. An exception is on Lurcher Shoals off southern Nova Scotia were temperatures were below normal through most of the year.

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