Reduced thiamine utilization by Seneca Lake lake trout embryos and potential implications to restoration of lake trout in the Great Lakes

Lake trout stocks in the Great Lakes basin show variability in the relationship between a thiamine-dependent early mortality syndrome (EMS) and egg thiamine (B1) concentration but the reasons are unclear. EMS has been linked to a diet of alewives and their high thiaminase activity. We examined the relationship among four alewife-dependent B1-deficient lake trout stocks, and determined B1 utilization rates for three of these stocks, and a non-alewife-dependent B1-replete stock. Although the EMS-B1 relationship was similar between an inland lake stock and Lake Ontario, there was almost no EMS in lake trout from two Finger Lakes: Cayuga (CL) and Seneca (SL) Lakes. B1 utilization rate for the SL stock was lower than for all other stocks. Similarity in the EMS-B1 relationship (CL, SL) and reduced thiamine utilization in the SL stock suggests that Finger Lakes lake trout are better able to cope with the low egg thiamine concentration resulting from an alewife diet. Reduced thiamine utilization during the embryonic stage, possibly as a result of adaptive genetic variation, may result in a greater contribution by Seneca Lake strain lake trout to wild lake trout populations in the Great Lakes.