The Reprofish working group has published a special booklet for the benefit of the aquaculture sector (stakeholder, fish farmers…), for the students, and for the public. This booklet provides a simplified overview of the knowledge on the reproductive biology of the major farmed fish species in Europe. In addition, it illustrates how basic and applied researches are used to improve the profit of the fish farms and to maintain the quality of products. Particularly, the use of biotechnological tools that allow one to control the sex ratio, to induce sterility, to delay/advance puberty, or to induce spawning, is introduced and discussed. Finally, the booklet presents other issues such as the sustainability of the aquaculture or the fish as a model animal for human frontier research.