Abstract
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.