Oceanic and Riverine Influences on Variations in Yield among Icelandic Stocks of Atlantic Salmon

Abstract

Abstract Data on yields of Atlantic salmon Salmo salar from 59 Icelandic rivers were analyzed with data on streamflows and sea and air temperatures in an attempt to identify why some stocks exhibited more variable yields than others. A group of 24 northern and northeastern rivers, which flowed into seas with wide annual variations in climatic and oceanic conditions (as indicated by coastal sea and air temperatures), exhibited significantly greater variation in Atlantic salmon yields of both grilse and two-sea-winter fish (two winters at sea before first spawning) than the 31 western rivers, which flowed into seas with more stable climatic and oceanic conditions. Yields were the most varied for stocks in the northeast, the region with the greatest annual variation in sea temperatures during spring and summer – the time when smolts migrate to the sea and begin to feed. Rivers with more variable seasonal streamflows also tended to have more variable two-sea-winter Atlantic salmon yields (P < 0.05) but not mo...