Early Life Stage Mortality Syndrome in Fishes of the Great Lakes and Baltic Sea

Interspecies Comparisons of Blood Thiamine in Salmonids from the Finger Lakes, and Effect of Maternal Size on Blood and Egg Thiamine in Atlantic Salmon with and without Cayuga Syndrome

J. P. Fisher, S. B. Brown, S. Connelly, T. Chiotti, and C. C. Krueger

doi: https://doi.org/10.47886/9781888569087.ch12

Abstract.—A lethal thiamine deficiency afflicting larval landlocked Atlantic salmon Salmo salar in several of New York’s Finger Lakes has been linked to a maternal diet of the exotic, thiaminase-rich alewife Alosa pseudoharengus. To evaluate why trout and char species in the Finger Lakes are apparently not affected by this “Cayuga syndrome,” levels of thiamine in the whole blood of syndromepositive and syndrome-negative stocks of Atlantic salmon were compared with levels in lake trout Salvelinus namaycush, brown trout Salmo trutta, and rainbow trout Oncorhynchus mykiss from Cayuga and/or Seneca lakes. Thiamine levels did not differ between sexes within any species or stock. Consistent with the hypothesis that thermal habitat partitioning may predispose the salmon to more dietary thiaminase than other Finger Lakes salmonids, thiamine levels in the salmon that produced syndrome-positive sac fry were significantly lower than levels measured in Finger Lakes brown trout and rainbow trout. In contrast, there was no difference between the syndrome-positive salmon and Finger Lakes lake trout, possibly because the male char were in starved (postspawned) condition. Regressions of maternal blood or egg thiamine versus maternal weight and length were not significant for salmon that produced syndrome-positive sac fry; yet, a significant inverse relationship was detected for the syndrome-negative salmon from the Adirondack progenitor stock. These findings may reflect the transition of these reference control salmon from a thiaminase-poor invertebrate diet to a piscivorous diet of thiaminase-active smelt Osmerus mordax.