Admixture analysis of simulated individuals in STRUCTURE. A total of 12 categories were simulated: pure European eel (AA), pure American eel (AR), F1 hybrid, F2 hybrid, first-generation backcross European eel × F1 (bAA), first-generation backcross American eel × F1 (bAR) and second-generation backcrosses (bAA × AA, bAA × AR, bAA × F1, bAR × AA, bAR × AR and bAR × F1). Average admixture proportion value and s.d. values are presented for each simulated category.