Atlantic salmon

Doctoral project:Thiamin dynamics in Atlantic salmon

The project focuses on thiamin deficiency in salmon in the Baltic Sea, a phenomenon that affects their behavior and offspring survival. By exploring thiamin dynamics in salmon, their diet history, and the role of gut microbiome and thiaminase, the project aims to understand the causes behind this deficiency.

Project information

Thiamin dynamics in Atlantic salmon: Investigating potential causes leading to deficiency in the Baltic Sea populations
Doctoral student

Vittoria Todisco
Samuel Hylander
Other project members
Marc Hauber, Emil Fridolfsson, Maciej Ejsmond, Petter Tibblin, Linnéuniversitetet; Kjetil Hindar, Norwegian Institute for Nature Research. Norway
Participating organizations

Linnaeus University, Norwegian Institute for Nature Research
Vetenskapsrådet and Linnéuniversitetet
1 Sept 2020–31 Dec 2024
Ecology (Department of Biology and Environmental Science, Faculty of Health and Life Sciences)

Food chain for the Atlantic salmon.
Thiamin is produced by lower trophic levels and is transferred up the food web. Picture: Marc Hauber

More about the project

Salmon and a range of other species are facing periods of deficiency of an essential micronutrient called thiamin. Thiamin, also known as vitamin B1 plays a crucial role in central metabolic functions, however, fish cannot produce it themselves. Instead, they rely on thiamin acquisition through the diet during the marine feeding phase. Salmon feeding then gradually decreases during the journey back to their natal rivers for spawning, leading to limited thiamin intake during this crucial period.

This poses a significant challenge, as the deficiency of this essential vitamin has been linked to behavioral and physiological abnormalities in adult salmon, as well as reduced survival rates for their offspring. Several salmonid species suffer from this deficiency, for example, Atlantic salmon (Salmo salar) in the Baltic Sea and Chinook salmon (Oncorhynchus tshawytscha) in the Great Lakes region, ultimately and possibly causing their populations to decline.

Recently, more species belonging to other groups have been suggested to be affected by this deficiency such as birds (e.g., common eider and herring gulls) and mussels.

The underlying cause to this deficiency is not well known. One potential cause is related to a thiamin-degrading enzyme called thiaminase, which can be found in certain prey items of salmon. Another factor involves the degradation of thiamin as it acts as an antioxidant during fat metabolism in adult salmon, leading to less available thiamin for the offspring.

Therefore, the aims of this project are:

  1. Understanding thiamin dynamics during the adult life cycle of Atlantic salmon by comparing ecosystems with documented thiamin deficiency and ecosystems where thiamin deficiency has never been observed.

  2. By using stable isotopes in fish eye lenses and analyzing fatty acids in salmon muscle, we are reconstructing salmon's diet history in order to investigate the potential role of susceptible fatty acids in oxidative stress and consequent thiamin storage depletion.

  3. Exploring the role of gut microbiome and thiaminase in thiamine deficiency.

  4. Describing physiological aspects of thiamin trade-offs between reproductive (gonads) and locomotory (muscle) tissues, with the final goal of developing a theoretical model based on fitness maximization.

The project is part of the research in the Food Web Ecology research group, Linnaeus University Centre for Ecology and Evolution in Microbial model Systems (EEMiS) and the Linnaeus Knowledge Environment Water.