This study was conducted to investigate the thiamine status of Chinook salmon Oncorhynchus tshawytscha. Egg thiamine levels in Yukon and Kuskokwim River Chinook were examined in 2001 and 2012. Muscle and liver thiamine in Chinook, coho O. kisutch, chum O. keta, and pink O. gorbuscha salmon were measured in northern Bering Sea juveniles and the percentage of the diet containing thiaminase, an enzyme that destroys thiamine, was calculated. Only 23% of the eggs were thiamine replete (> 8.0 nmol·g-1) in 2012. Seventy-four percent of the eggs had thiamine concentrations (1.5–8.0 nmol·g-1) which can lead to mortality from secondary eff ects of thiamine defi ciency. Only 3% of the eggs had < 1.5 nmol·g-1 associated with overt fry mortality. In 2001 egg thiamine in upper Yukon Chinook was 11.7 nmol·g-1 which was higher than that measured in 2012 (6.2 nmol·g-1) and paralleled Chinook productivity. Total thiamine (nmol·g-1) in Bering Sea Chinook muscle (3.8) was similar to coho (4.15), but lower than in chum (8.9) and pink salmon (9.6). Thiaminase-containing prey in Chinook (63%) and coho (36%) stomachs were elevated compared to those of chum (3%) and pink (5%) salmon. These results provide evidence of egg thiamine being less than fully replete. Thiamine deficiency was not observed in juvenile muscle tissue, but differences were present among species reflecting the percentage of diet containing thiaminase. Additional studies are recommended.
