Feeding of Atlantic salmon (Salmo salar L.) post-smolts in the Northeast Atlantic

Abstract

Abstract Stomach samples from 1384 Atlantic salmon, collected from 1991 to 2003 in the Northeast Atlantic, were analysed to fill the gap between studies on post-smolt diet in fjords and coastal areas of the Northeast Atlantic and studies on the diet of pre-adults and adults in the Norwegian Sea. The post-smolts fed largely on 0-group fish. Blue whiting was an important prey only in the slope current transporting the larvae from the spawning areas west of the United Kingdom into the North and Norwegian Seas. Sandeel and herring were important or present in the stomachs throughout most of the area studied. Unusually large quantities of 0-group herring in the Norwegian Sea in summer 2002 coincided with a high condition factor of post-smolts that year. The forage ratio of the post-smolts was positively related to the proportion of herring in the stomachs and the abundance of herring recruits. Despite these findings, the most productive period for Atlantic salmon on record, the 1970s, coincided with the collapse of the Norwegian spring-spawning herring, which raises the question as to whether herring is more important as a competitor than as a food source. Hyperiid amphipods were more important prey than krill, in contrast to the situation for other pelagic fish species.