Thiamine (Vitamin B1) concentrations in salmon (Salmo salar), brown trout (Salmo trutta) and cod (Gadus morhua) from the Baltic Sea

During recent decades several Baltic fish species have been affected by poor reproductive success. The sea-run Baltic salmon populations are affected by the M74 syndrome, an early life-stage mortality associated with low thiamine (vitamin B1) concentrations in the offspring. In order to study whether sea-run brown trout with symptoms and mortalities similar to M74 also suffer from low thiamine concentrations, analyses of thiamine were performed. Also, tissues of Baltic cod were analyzed for their content of thiamine. This study confirms that Baltic salmon that are affected by M74 suffer from low thiamine levels and that the temporal onset of the development of M74 may be correlated to the thiamine concentration in the eyed egg. Also, thiamine concentrations of muscle and ovaries from females that produced offspring with M74 were significantly lower than those of females that produced healthy progeny, which indicates that M74 may be a maternally transmitted thiamine deficiency. Preliminary data from sea-run Baltic brown trout showed that yolk-sac fry with symptoms that resembled those of M74-lethargy, darkening of skin and 100% mortality-had low mean thiamine concentrations ($0.14\ {\rm nmol}\ {\rm g}^{-1}$in 1994 and 0.34 in 1998) compared with those of healthy progeny ($4.4\ {\rm nmol}\ {\rm g}^{-1}$in 1994 and 3.9 in 1998). This indicates that some family groups of Baltic brown trout may be affected by a reproduction disorder related to thiamine deficiency. In spawning Baltic cod, hepatic and ovarian thiamine concentrations showed great variance, with values ranging from 0.56 to 4.7, and 3.8 to$30\ {\rm nmol}\ {\rm g}^{-1}$, respectively. Whether Baltic cod also suffer from mortality associated with a thiamine deficiency is not known.