Low thiamine concentrations are associated with altered cardiac morphology across reproductive life histories of spawning Chinook Salmon.

Objective: Thiamine deficiency is a widespread issue in salmonine species and has been reported to induce changes in cardiac morphology and cardiac dysfunction in Lake Trout Salvelinus namaycush. Here, we assess the effects of thiamine concentration on the ventricular morphology of three reproductive life histories (jack males, hooknose males, and females) of wild spawning Chinook Salmon Oncorhynchus tshawytscha.

Methods: Fish were sampled from the Credit River (a Lake Ontario tributary), and skeletal muscle, ventricle, and liver thiamine concentrations were quantified using high-performance liquid chromatography. A subset of ventricles was retained for histological analyses. Hematoxylin and eosin-stained slides were used to measure cardiomyocyte width and compact myocardium thickness, and Masson's trichrome-stained slides were used to measure levels of cardiac fibrosis. Level of spawning senescence was quantified based on a qualitative score.

Results: Thiamine levels did not differ significantly among life histories, except that hooknose males had significantly greater skeletal muscle thiamine concentrations than females. Thiamine concentrations in skeletal muscle and the ventricle were positively correlated. Across all life histories, lower concentrations of thiamine in skeletal muscle were associated with increased levels of cardiomyocyte hypertrophy and cardiac fibrosis, independent of their relationships with ventricle mass and level of spawning senescence. No significant relationships were observed with compact myocardium thickness.

Conclusions: Low thiamine concentrations are associated with pathological alterations in cardiac morphology across reproductive life histories in spawning Chinook Salmon.