Production of YY rainbow trout males by self-fertilization of induced hermaphrodites.

Dietary administration of various estrogens for three months from swim-up stage resulted in excess of females, the remainder of the treated groups consisting of males and hermaphrodites. Mature hermaphrodites were self-fertilized or mated with standard males and females. These hermaphrodites and some of the estrogen-treated females proved to be genetic males; the frequencies of males obtained from their ova averaged 76.6%, suggesting viability of the YY genotype. Four of nine tested males of those progenies provided all male offspring when mated with standard females.