Thiamine Concentrations in Feral Baltic Salmon Exhibiting the M74 Syndrome
P. Amcoff, H. Börjeson, J. Lindeberg, and L. Norrgren
Abstract.—Since 1974, feral Baltic salmon Salmo salar populations have suffered from yolk sac fry mortality caused by the M74 syndrome. This syndrome affects yolk sac fry originating from specific females, and the mortality in affected family groups is usually 100%. Since 1990–1991, disturbances in the behavior of spawning migrating Baltic salmon have been observed. This study found a strong correlation between wiggling behavior in adult female Baltic salmon and the development of M74 in their offspring. Moreover, the ovarian thiamine concentrations in wiggling females were found to be significantly lower than those of females with normal behavior. In addition, eyed eggs and yolk sac fry that subsequently developed M74 contained only 13% (0.24 nmol/g) and 6% (0.11 nmol/g), respectively, of the thiamine concentrations detected in viable progeny sampled during the same periods. Eyed eggs with thiamine concentrations below a threshold limit interval of 0.36–0.77 nmol/g were found to have a high risk of developing M74 at the yolk sac fry stage.