Thiaminase activity of gastrointestinal contents of salmon and herring from the Baltic Sea

Potential thiaminase activity of Baltic herring Clupea harengus ranged from 0 to c. 55 nmol g‐1 min‐1 while potential thiaminase activity in Baltic salmon Salmo salar gastrointestinal (GI) contents ranged from 7 to c. 60 nmol g‐1 min‐1. About 30% of the Baltic herring analysed had a potential thiaminase activity equivalent to Baltic salmon GI contents. The results are consistent with the hypothesis that thiaminase in the forage fish of Baltic salmon may be an important link in the aetiology of the thiamine deficiency syndrome, M74, in Baltic salmon and indicate that Baltic salmon might feed selectively on Baltic herring with high thiaminase activity.