Poor feeding opportunities and reduced condition factor for salmon post-smolts in the Northeast Atlantic Ocean. (25th August 2021)

• Record Type: Journal Article
• Authors: Utne, Kjell Rong; Pauli, Beatriz Diaz; Haugland, Monika; Jacobsen, Jan Arge; Maoileidigh, Niall; Melle, Webjørn; Broms, Cecilie Thorsen; Nøttestad, Leif; Holm, Marianne; Thomas, Katie; Wennevik, Vidar
• Editors: Secor, David
• Is Part Of: ICES journal of marine science. Volume 78:Number 8(2021)
• Page Start: 2844
• Page End: 2857
• Publication Date: 2021-08-25
• Subjects: amphipoda -- climate change -- fish larvae -- mackerel -- Norwegian Sea; Ocean -- Periodicals; Fisheries -- Periodicals; Fishes -- Periodicals; Marine biology -- Bibliography -- Periodicals; 551.4605
• DOI: 10.1093/icesjms/fsab163
• Languages: English
• ISSNs: 1054-3139

Abstract

Abstract: During the last few decades, many wild Atlantic salmon populations have declined dramatically. One possible contributing factor for the decline is reduced prey availability at sea. Here, we examine post-smolt diet and investigate if post-smolts show signs of selective feeding based on 2546 post-smolts sampled from west of Ireland to the northern Norwegian Sea over a 25-year period. We also test for changes over time in stomach fullness, diet, condition factor and body length. There was a clear reduction in condition factor for post-smolts sampled in the Norwegian Sea in the period 2003–2012. The post-smolt stomach fullness was also reduced in the same period. The reduction in condition factor is partly explained by reduced stomach fullness, including a reduction of highly energetic fish larvae and Amphipoda in the diet. Feeding on other prey, such as meso-zooplankton and insects, cannot substitute the high-quality fish larvae and Amphipoda in the post-smolt diet. This is the first study to document how salmon post-smolts feeding in the Norwegian Sea are affected by reduced feeding conditions. Possible causes for the observed changes in post-smolt feeding are ocean warming, decreased primary productivity, and reduced recruitment of important fish larvae.