The body temperature of fish is predominantly influenced by the temperature of the surrounding water. Fish are ectothermic, meaning they rely on their environment to regulate their body temperature. As the water temperature changes, so does the body temperature of the fish, impacting their metabolic processes, activity levels, and overall physiology. Various factors, such as seasonal fluctuations, depth in the water column, thermal stratification in larger bodies of water, and their own behavior, can contribute to these temperature variations.