The effect of diet-derived thiaminase on survival, growth, and liver transketolase activity in two strains of lake trout (Salvelinus namaycush)

The consumption of invasive, high-thiaminase prey fishes can cause thiamine deficiency, which has been hypothesized to be a major barrier for lake trout ( Salvelinus namaycush ) restoration in the Laurentian Great Lakes. Here, we compared the effects of diet-derived thiaminase on survival and performance-related traits between two strains of lake trout that differ in historical exposure to thiaminase. Juvenile lake trout from the Seneca Lake (higher historical exposure to thiaminase) and Slate Islands (lower historical exposure) strains were reared in a common garden environment and received either an experimental diet containing bacterial derived-thiaminase or a control diet. Six months after the initiation of the experimental diets, survival, liver transketolase activity, growth, and food conversion efficiency were compared between strains and treatments. Unexpectedly, both diets resulted in liver transketolase latency values that were consistent with thiamine deficiency, and this was true for both strains. The thiaminase diet had larger negative effects on growth, food conversion efficiency, and survival compared to the control diet, and, except for survival, these effects did not differ between the two strains. Fish from the Seneca Lake strain had lower survival when fed the thiaminase diet than when fed the control diet; no difference in survival was found between diets fed to the Slate Islands fish, which was unexpected given their lower historical exposure to thiaminase. Our results confirm the negative effects of thiaminase in lake trout and identify potential strategies that could mitigate effects via strain selection.