Increased Cold Tolerance of a Tropical Fish Species at the Northern Edge of Its Expanded Range Estuaries and Coasts

As climate change leads to rising temperatures, tropical fishes such as common snook Centropomus undecimalis (hereafter snook) are expanding poleward, necessitating an understanding of their ability to tolerate cold temperatures and rapid temperature drops. To investigate this ability, we conducted chronic lethal minimum (CLmin) and critical thermal minimum (CTmin) trials in the laboratory using fish collected from a latitudinal gradient along the Gulf of Mexico coast of Florida. Individual lower lethal temperatures ranged from 7.9 to 10.5 °C. On average, the northernmost snook population exhibited the most cold hardiness, ceasing feeding at 14.4 °C and dying at 8.6 °C. These thermal endpoints were lower than for populations collected farther south and are significant in the context of passing cold fronts. In the CTmin trial that reduced water temperatures more quickly, and is sub-lethal, snook lost equilibrium at temperatures almost 2 °C warmer than those in our chronic trial, underscoring the necessity of simulating realistic cold events to fully understand species’ cold tolerance. These findings help managers predict the effects of variation in timing and extent of severe cold events on snook across different estuaries, allowing for targeted management approaches should conditions warrant actions to facilitate population recovery. Metrics associated with a species’ cold hardiness can inform climate modeling, fisheries management, and freshwater inflow regulations affecting thermal refugia, aiding in the management and conservation of tropical fish populations in the face of global climate change.

随着气候变化引发气温升高，诸如常见锯盖鱼（Centropomus undecimalis，下称锯盖鱼）这类热带鱼类正向极地海域扩张，因此亟需明确其对低温环境以及温度骤降的耐受能力。为探究该耐受特性，本研究依托从佛罗里达州墨西哥湾沿岸沿纬度梯度采集的锯盖鱼，在实验室中开展了慢性最低致死温度（chronic lethal minimum, CLmin）与临界最低致死温度（critical thermal minimum, CTmin）两项试验。试验结果显示，个体的最低致死温度区间为7.9至10.5 ℃。平均来看，最北部的锯盖鱼种群耐寒性最强，在14.4 ℃时停止摄食，于8.6 ℃时死亡；该热耐受阈值较南部采集的种群更低，在应对寒潮的场景中具备重要参考价值。在降温速率更快的亚致死CTmin试验中，锯盖鱼丧失平衡时的水温较慢性试验组高出近2 ℃，这凸显了模拟真实冷事件对于全面解析物种耐寒性的必要性。本研究结果可帮助管理者预测极端冷事件的发生时序与强度差异对不同河口地区锯盖鱼种群的影响，在环境条件需要采取行动以促进种群恢复时，可为针对性管理措施的制定提供依据。与物种耐寒性相关的指标可为气候建模、渔业管理以及影响温度避难所（thermal refugia）的淡水径流调控法规提供参考，助力全球气候变化背景下热带鱼类种群的管理与保护工作。