Data from: Sire x dam interactions and male-biased mortality determine sex ratios in brown trout embryos

Juvenile sex-ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = prop. males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39  0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire x dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates对于许多具有遗传性别决定（genetic sex determination）机制的物种而言，幼体性比通常被假定为均等，但由于鱼类胚胎体型微小且缺乏性别特异性标记（sex-specific markers），相关假说极少在鱼类胚胎中得到验证。本研究对三个褐鳟（brown trout）种群进行人工杂交，并借助新近开发的性别鉴定遗传标记，对纯合杂交与异源杂交子代的性别进行分型。孵化一个月后测得的性比（SR=雄性比例）波动范围极广，介于0.15至0.90之间（平均值为0.39±0.03）。存活率较高的家系往往呈现出性比均衡或偏雄性的特征；而当存活率较低时，性比则显著偏雌性，这表明雄性在发育过程中承受了更高的死亡率。纯合家系与杂交家系的性比并无显著差异，但父本×母本互作现象的存在，暗示遗传不相容性（genetic incompatibility）可能在性比决定过程中发挥作用。本研究结果对动物育种与物种保护具有借鉴意义：偏态性比往往会降低有效种群大小（effective population size），并对选择估计值（selection estimates）造成偏差。