Immersing thiamine-deficient eggs and fry in water with added thiamine to reduce early mortality of fry of Atlantic salmon

Atlantic salmon (Salmo salar) consuming thiaminase-containing forage fishes (i.e., alewives) often produce fry that suffer high mortality caused by thiamine deficiency.  Hatchery managers reduce this mortality, with varying success, by immersing eggs or fry in thiamine solutions. To better define the optimum strategy to prevent thiamine-deficiency mortality of fry near first-feeding, we conducted replicated immersion experiments using fertilized eggs and fry from thiamine-deficient Atlantic salmon captured in Cayuga (Lake) Inlet.  During water-hardening, 1-hr immersion of eggs in 1,000 and 5,000 PPM thiamine reduced fry mortality to 78 and 49%, respectively, compared to controls (100%). Immersion of eyed eggs provided no benefit. Immersion of newly-hatched fry for 1 hr in 1,000 PPM thiamine did not significantly (P>0.05) reduce mortality (90%); whereas immersion in 5,000 PPM thiamine for 6 hours significantly (P<0.01) reduced mortality (6%).   Mortality of fry immersed in 1,000 PPM thiamine for 6 or 24 hr was 40 and 4%, respectively. In conclusion, we found no optimum strategy for eggs. For fry, optimum duration of immersion in 1,000 PPM thiamine was more than 6 hr but not more than 24 hr; whereas in 5,000 PPM thiamine, the optimum duration was more than 1 hr but not more than 6 hr.