The vulnerability of fish populations to climate change is driven primarily by impacts on their most vulnerable life stages. The earliest life stages may, in many cases, be more thermally sensitive than juvenile and adult fish, as developing embryos cannot behaviourally thermoregulate. We quantified the survivorship of brook trout (Salvelinus fontinalis) embryos under a range of winter thermal regimes. In the laboratory, embryos from four populations with varying amounts of native or hatchery-introgressed ancestry were reared under four simulated winter thermal regimes relevant to the central portion of the species’ range: ambient stream temperatures, ambient + 2 °C, ambient with a simulated winter snowmelt event, and ambient followed by an early rise to spring temperatures. Embryo survival (hatching success) differed significantly among populations across all thermal regimes, with the pure native population having the lowest survival. No consistent differences in survivorship across thermal regimes were detected, although native populations exhibited more among-family variability in response to thermal stress. Our study does not align closely with others that found reduced embryo survival under thermal stress, but concurs with observations of substantial intraspecific variation in thermal performance in coldwater fishes. Our results suggest that brook trout embryos may be somewhat resilient in the face of warmer and more variable incubation conditions, but it is likely that their resiliency varies among populations. Future experiments that include more extreme and variable conditions to clarify environmental limits of early life stages of brook trout would be useful for conservation planning.

鱼类种群对气候变化的脆弱性主要是由于对其最脆弱的生命阶段的影响造成的。在许多情况下，最早的生命阶段可能比幼鱼和成鱼对热更敏感，因为发育中的胚胎无法进行温度调节。我们量化了在一系列冬季热条件下溪鳟（ Salvelinus fontinalis ）胚胎的存活率。在实验室中，来自具有不同数量本地或孵化场渗入祖先的四个群体的胚胎在与物种范围的中心部分相关的四个模拟冬季热状况下培育：环境流温度、环境+2°C、环境温度模拟冬季融雪事件，以及随后春季气温提前上升的环境。在所有热状态下，胚胎存活率（孵化成功率）在种群之间存在显着差异，纯本地种群的存活率最低。尽管本地种群对热应激的反应表现出更多的家庭间差异，但没有检测到不同热状态下存活率的一致差异。我们的研究与发现热应激下胚胎存活率降低的其他研究并不一致，但与冷水鱼热性能的种内差异的观察结果一致。我们的结果表明，面对温暖和多变的孵化条件，溪鳟胚胎可能具有一定的弹性，但它们的弹性可能因种群而异。未来的实验包括更极端和多变的条件，以澄清溪鳟早期生命阶段的环境限制，这将有助于保护规划。