Ecophysiological patterns of distribution and behavior of freshwater fish in thermal gradients

Abstract

Species-specific, intraspecific, age-related, seasonal, diel, physiological, and behavioral aspects of the distribution of freshwater fishes along experimental and natural thermal gradients are analyzed. It is shown that thermal selection response is displayed by all fish species. The thermal selection process includes two stages: the choice of the current selected temperature, which reflects the acclimation process, and the choice of the final selected temperature, which follows the stabilization of thermal selection. Thermoregulation behavior is an inherent reaction and can be placed among the most shared and earliest adaptations of aquatic animals. The final selected temperature of fishes reflects the ecophysiological optimum of the existence of the species, and the upper lethal temperature reflects the limit of potential existence.