Early maturation of Atlantic salmon male postsmolts is undesirable in aquaculture due to its negative impact on growth, welfare and seawater adaptation, however it is an increasing problem under intensive rearing conditions. The effect of temperature and feeding ration on sexual maturation during the induction of smoltification was tested with a 3 × 2 factorial design including three temperatures (8, 12.5 and 18 °C) and two feeding rations (100% and 67%), from 28 October 2018 to 30 May 2019. Fish in the six resulting treatments (1800 parr, initial mean weight 23.1 ± 7.2 g) were reared in flow-through under continuous light (LD24:0) except for a 5-week winter signal (LD12:12) introduced on 4 February 2019 to induce smoltification. A major effect of temperature determining the life history pattern of each group was observed. At 18 °C, a majority of the males were maturing in May under both rations (100% males in 18–100% and 88.9% males in 18–67%). Fish at 18 °C experienced an early activation of the BPG (Brain-Pituitary-Gonad) axis and displayed very poor signs of smoltification. At 12.5 °C, early maturation was also present, although at lower proportion than at 18 °C and more dependent upon feed ration (40% of males maturing in 12.5–100%, 8.6% in 12.5–67%). Salmon at 12.5 °C displayed the best growth within each feed regime, some early signs of smolting but subsequent low Na⁺, K⁺- ATPase activity after the winter signal. At 8 °C, salmon showed best signs of smoltification and lowest growth, while no males matured. The feed restriction had a minor effect on maturation at 18 °C but a greater impact at 12.5 °C, evidenced by significant differences between 12.5 and 100% and 12.5–67% in gonadosomatic index, plasma 11-ketotestosterone, insulin-like growth factor-I, and pituitary fshb (follicle stimulating hormone β-subunit gene) transcription. Onset of maturation was associated with the photoperiod change from short to long daylength, which probably also induced a slight activation of the BPG axis in non-maturing groups. Our results suggest that postsmolt producers must be cautious when using sustained high water temperatures, or the risk of early maturation and poor hypo-osmoregulatory performance will increase significantly. In addition, reducing the feeding ration will not help decrease incidence of maturation without significantly affecting growth.

大西洋鲑雄性蜕皮后的早期成熟在水产养殖中是不可取的，因为它对生长、福利和海水适应产生负面影响，但在集约化饲养条件下它是一个日益严重的问题。用 3 × 2 因子设计测试温度和饲喂量对诱导熏蒸过程中性成熟的影响，包括三个温度（8、12.5 和 18 °C）和两个饲喂量（100% 和 67%），从 28 2018 年 10 月至 2019 年 5 月 30 日。除了 5 周的冬季信号（LD12： 12) 于 2019 年 2 月 4 日引入以诱导冶炼。观察到温度决定每组生活史模式的主要影响。在 18 °C 时，大多数雄性在 5 月在两种日粮下成熟（18-100% 为 100% 雄性，18-67% 为 88.9% 雄性）。18°C 的鱼经历了 BPG（脑-垂体-性腺）轴的早期激活，并显示出非常差的 smoltification 迹象。在 12.5 °C 时，也存在早熟，尽管比例低于 18 °C，并且更多地取决于饲料配给（40% 的雄性在 12.5-100% 中成熟，8.6% 在 12.5-67% 中成熟）。三文鱼在 12.5 °C 的温度下在每种饲料方案中都表现出最好的生长，有一些早期的发烟迹象，但随后是低钠 尽管比例低于 18 °C 且更多地取决于饲料配给（40% 的雄性在 12.5-100% 中成熟，8.6% 在 12.5-67% 中成熟）。三文鱼在 12.5 °C 的温度下在每种饲料方案中都表现出最好的生长，有一些早期的发烟迹象，但随后是低钠 尽管比例低于 18 °C 且更多地取决于饲料配给（40% 的雄性在 12.5-100% 中成熟，8.6% 在 12.5-67% 中成熟）。三文鱼在 12.5 °C 的温度下在每种饲料方案中都表现出最好的生长，有一些早期的发烟迹象，但随后是低钠⁺ , K ⁺ - 冬季信号后的 ATPase 活性。在 8 °C 时，鲑鱼表现出最佳的鱼腥化迹象和最低的生长，而没有雄性成熟。限食对 18 °C 的成熟度影响较小，但在 12.5 °C 的影响更大，这可以从性腺体指数、血浆 11-酮睾酮、胰岛素样生长因子 12.5% 和 100% 以及 12.5-67% 之间的显着差异证明-I，垂体fshb（促卵泡激素β亚基基因）转录。成熟的开始与光周期从短到长的变化有关，这可能也导致非成熟组中 BPG 轴的轻微激活。我们的研究结果表明，蜕皮后生产者在使用持续的高水温时必须谨慎，否则早熟和低渗透压性能不佳的风险将显着增加。此外，减少饲喂量无助于降低成熟率，但不会显着影响生长。