Intraspecific diversity is of paramount importance for species adaptation to global changes. Alternative mating tactics have important ecological and evolutionary implications and are determined by complex interaction between environmental and genetic factors potentially involving phenotypic plasticity. Atlantic salmon is a good example of species showing high life history variability. Here we focused on early male parr maturation, an alternative reproductive tactics allowing male parr to reproduce before the seaward migration. The research project GenEarly combines experimental ecology, quantitative genetics and population genomics approaches and use the state of the art in sequencing technology to shed new light on the genetic determinism and the genomic architecture on alternative reproductive tactics in Atlantic salmon natural populations. In the first part of the project, we applied a mixed experimental design including controlled crosses and rearing of offsprings in a semi-natural channel. This allowed us to implement the Environmental Threshold model, a statistical framework derived from the field quantitative genetic, in a realistic ecological setting. Specifically, we tested for the effect of the reproductive phenotype of the sire on the reproductive phenotype of the offspring,by crossing female to anadromous male and early mature parr. We found evidence for environmentally induced differences, but no genetic effect, on the liability distribution (spring weight). However, we showed that offsprings from early mature males present a much higher early maturation rate (84.6%) compared to offsprings from nadromous male (28.9%). These results demonstrate a strong paternal inheritance of the threshold reaction norms for alternative mating strategy that could be explained by sex-linked genetic factor or / and transgenerational epigenetic paternal effects. Genomic (QTL and genome scan using Genotyping By Sequencing) and transcriptomic (RNAseq) approaches are underway to help resolving this unexpected paternal inheritance. The bioinformatics challenge arising from these data intensive methods will be much relieved by the release of the Atlantic salmon reference genome. Integrating the different approaches should produce new understanding about genetic potentialities and constraints for reproductive behavior evolution in face of global changes with a particular focus on improving evolutionary trajectory predictability and conservation practices.