Individual variation in fatty-acid and thiamine concentrations were determined in lake trout Salvelinus namaycush eggs collected at two spawning grounds in Lake Michigan. A suite of predictor variables, including spawning location, egg fatty-acid and thiamine concentrations, were used to attempt to explain cause-and-effect in early life stage mortality among S. namaycush families. Lipid and fatty-acid composition of S. namaycush eggs differed between spawning locations. Salvelinus namaycush offspring from south-western Lake Michigan were affected by a high occurrence of yolk oedema, whereas a higher frequency of early mortality syndrome (EMS) was observed among offspring from the north-western part of the lake. Random-forest regressions revealed location as the most influential predictor of yolk oedema mortality, whereas thiamine level in eggs was the strongest predictor of EMS-related mortality. Several polyunsaturated fatty acids were also found to be predictors of both mortalities. There is evidence of spatial variability in egg fatty-acid concentration among S. namaycush in Lake Michigan that, together with diminished thiamine concentration, contribute to low survival of S. namaycush progeny.
© 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.