What is it about?

The new research reports on the cause, extent, and impact of thiamine (also known as vitamin B1) deficiency in salmon in California. A multi-agency research group examined thiamine deficiency in California salmon, which was first observed in 2020. Thiamine is mainly acquired by diet, and multiple lines of evidence point at a shift to an anchovy-dominated forage base and diet as the proximate cause for the emergence of this new stressor on California salmon. Significantly, anchovy contain an enzyme that breaks down thiamine in its predator’s stomach when digested.

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Why is it important?

A deficiency of thiamine has long been recognized as a severe human disease known as beriberi, but thiamine deficiency also threatens wildlife, including salmon and their relatives. Understanding thiamine deficiency is critical not only for protecting ecologically important salmon and salmon fisheries, but effects on salmon could be an early warning sign for many other susceptible species, including marine mammals and seabirds.

Perspectives

The longtime loss of habitat and access to both high elevation cold water streams and productive shallow-water floodplains have already weakened many California salmon populations. Further declines from thiamine deficiency or other impacts may lead to prolonged fishery closures or even extinction for some populations. While thiamine deficiency has not been widely known as a problem for Pacific salmon in their native range, it has been detected in some Alaska salmon populations. Researchers so rarely test for thiamine deficiency that it may be more widespread in Pacific salmon populations than had been known.

Nate Mantua

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This page is a summary of: Widespread thiamine deficiency in California salmon linked to an anchovy-dominated marine prey base, Proceedings of the National Academy of Sciences, June 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2426011122.
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