The aim of the present work was to compare the reproductive characteristics of males and females from two divergent lines of spring-spawning rainbow trout, selected for high (fat line, FL) or low (lean line, LL ) muscle lipid content. Muscular lipid content influences precocious puberty in 1 year-old males and in 2 year-old females, as well as the kinetics of gametogenesis. The relationship between the different phases of gametogenesis and fat reserves are discussed.