Water temperature controls a plethora of morphological and metabolic functions in fishes and studies examining thermal tolerance of fishes and the responses of fishes to changing water temperatures have been conducted for over a century. Although there has been a renewed interest in the management and conservation of alligator gar, currently there are no data regarding the thermal minima of the species. In this study, we obtained alligator gar juveniles from a hatchery setting, acclimated these fish to three separate water temperatures (21, 24.5, and 28°C) and then subjected them to critical thermal minima trials to quantify lower thermal tolerance. Critical thermal minima results were found to be related with acclimation temperature and total length. Less developed gar experienced equilibrium loss at higher temperatures than larger, more developed gar. Also, alligator gar in the coldest acclimation trials (21°C) were able to tolerate the lowest temperatures. The mean CT_min temperature values obtained for each acclimation trial were 11.57°C, SD = 1.39 (21°C), 12.83°C, SD = 1.47 (24.5°C), and 14.16°C, SD = 1.60 (28°C). This study helps to fill an important data gap in alligator gar life history, and our results could be beneficial for management of alligator gar and determining potential future range distributions.

中文翻译：

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鳄鱼雀 (Atractosteus spatula, [Lacépède, 1803]) 在生命早期阶段的临界热最小值

水温控制着鱼类的大量形态和代谢功能，一个多世纪以来一直在研究鱼类的耐热性和鱼类对水温变化的反应。尽管人们对鳄鱼雀的管理和保护重新产生了兴趣，但目前没有关于该物种最低体温的数据。在这项研究中，我们从孵化场环境中获得了鳄鱼幼鱼，让这些鱼适应了三个不同的水温（21、24.5 和 28°C），然后对它们进行临界热最小值试验以量化较低的热耐受性。发现临界热最小值结果与驯化温度和总长度有关。较不发达的 gar 在较高的温度下比较大的 gar 经历平衡损失，更发达的gar。此外，鳄鱼雀在最冷的适应试验 (21°C) 中能够耐受最低温度。平均 CT每次驯化试验获得的_最低温度值为 11.57°C，SD  = 1.39（21°C），12.83°C，SD  = 1.47（24.5°C）和 14.16°C，SD  = 1.60（28°C）。这项研究有助于填补鳄鱼雀生活史中的一个重要数据空白，我们的结果可能有利于鳄鱼雀的管理和确定未来潜在的分布范围。