Maternal blood, egg and larval thiamin levels correlate with larval survival in landlocked Atlantic salmon (Salmo salar)

A link was previously established between the Cayuga syndrome, a condition causing 100% mortality in larval landlocked Atlantic salmon, Salmo salar, i n several of New York's Finger Lakes, and a maternal diet of alewife, Alosa pseudoharengus, a non-native thiaminase-rich Clupeid fish. We evaluated sa lmon larvae viability relative to maternal thiamin status, and investigated the putative link of the Cayuga syndrome to an alewife diet in fish from t he geographic regions outside the Finger Lakes/lower Great Lakes watersheds . We identified Cayuga syndrome in Atlantic salmon from Otsego Lake in the Susquehanna River watershed and from Green Pond in New York's Adirondack Mo untains. In both systems alewife represent the major component of the diet for the salmon. Thiamin levels in the maternal blood of Otsego salmon with syndrome-negative progeny were three- to four-fold greater than those Otseg o females whose progeny exhibited 100% mortality. Thiamin levels in eggs an d larvae were directly related to thiamin levels in maternal blood in both syndrome-positive and syndrome-negative stocks. Thiamin bath treatments of syndrome-afflicted larvae eliminated mortality regardless of their lake sto ck of origin. Maternal blood levels of approximately 0.31 nmol thiamin pyro phosphate/g or 0.44 nmol total thiamin/g appear necessary to achieve egg th reshold levels of approximately 0.8 and 1.1 nmol/g unphosphorylated and tot al thiamin, respectively; these egg thiamin levels should prevent significa nt syndrome-related mortality in landlocked Atlantic salmon larvae. These r esults confirm the role of thiamin in the etiology of the Cayuga syndrome a nd support the dietary link of this naturally occurring thiamin deficiency to the thiaminase-rich alewife.