Diet-induced declines in thiamine concentration threaten the cardiac health of wild sub-adult Chinook salmon

Abstract

Thiamine (vitamin B₁) is an essential vitamin involved in energy metabolism. Despite its importance, thiamine deficiency is a widespread issue among wildlife. Thiamine deficiency is particularly prevalent among salmonine fishes, in which it is diet-induced and has been associated with detrimental changes to cardiac morphology and function. Here, we assessed the diet, thiamine concentration, and ventricular morphology of sub-adult Chinook salmon (Oncorhynchus tshawytscha) in lakes Huron and Ontario. Stomach content analyses revealed distinct dietary differences between lakes. Chinook salmon from Lake Huron, which primarily consumed rainbow smelt (Osmerus mordax), had significantly higher skeletal muscle and ventricle thiamine concentrations compared to those from Lake Ontario, where their diet mainly consisted of alewife (Alosa pseudoharengus). Histological analyses of cardiac ventricles revealed that low ventricle thiamine concentrations were associated with detrimental changes to ventricular morphology including cardiomyocyte hypertrophy, degeneration, fibrosis, and changes in compact myocardium thickness. Altogether, this work demonstrates that low thiamine concentrations could threaten the cardiac health of wild salmonines, with important implications for their conservation and management.