Within the Sole hatchery project we are executing some interesting trials to improve the performance of the juvenile sole. In short we have found a mechanism that can influence the sex-ratio of the juvenile fish. We want to have more female than male fishes. When the fish is getting older, the females grow faster than the male individuals. In the experiments we are running at the moment we are looking to find the right moment and conditions to get the highest percentage of female fish.... and the best part is.... we do this completely in a natural way!