Effects of a High Thiaminas Diet on Sub-Adult Atlantic Salmon

Atlantic salmon were once abundant in Lake Ontario, but were extirpated by 1900. Recent restoration attempts have yet to succeed in establishing a self-sustaining population, possibly because of a thiamine deficiency due to introduced high thiaminase-containing alewife and rainbow smelt. It is unknown whether there are genetic adaptations to thiamine deficiency resistance. We examined the effects of a thiaminase diet on sub-adult (two-year-old) Atlantic salmon from three populations (LaHave, Sebago, and Saint-Jean) that are being used for reintroduction into Lake Ontario. The thiaminase diet, mimicking the current high thiaminase activity of prey fishes, was produced by mixing bacterial thiaminase into prepared feed. After 3 months of diet, salmon had half the swimming speed relative to the control diet. After 6 months of diet, we found a higher reduction in liver thiamine in the LaHave population relative to the Sebago and Saint-Jean populations. While salmon had no change in survival and growth after 6 months of diet, the salmon had whiter bodies and darker backs, were lower in condition, had a less streamlined body shape, and had lower thiamine content in red blood cells and liver. The changes in those later traits may negatively impact Atlantic salmon future survival.