Hypoxia is amongst the most widespread and pressing problems in aquatic environments. For the first time, we demonstrate that fish (Oryzias melastigma) exposed to hypoxia show reproductive impairments in F2 generations despite these progenies (and their germ cells) having never been exposed to hypoxia. We further show that the observed transgenerational reproductive impairments are associated with a differential methylation pattern of specific genes in sperm of both F0 and F2. Overall design: Examination of Methylated DNA immunoprecipitation on 4 groups (F0N, F0H, F2T, F2H)