This paper aims was to investigate the changes of some important physiological indices (energy metabolism, respiratory rate, number of red blood cells, blood glucose level, survival) for perch ( Perca fluviatilis L.), exposed to the action of Talstar One insecticide under different temperature conditions (18-20ºC and 6-8°C). Talstar One insecticide had a similar effect on the oxygen consumption, translated into a stimulating phase, particularly for samples adapted to room temperature, usually in inverse proportion to the concentration, followed by a slower reduction period or stabilization of the physiological indices. The average number of red blood cells decreased after 14 days from the fish immersion in insecicide. The fish adapted to temperatures of 6-8°C recorded significant decreases in the number of red blood cells and increases in blood glucose levels. Talstar One increased the blood glucose level after two weeks of exposure. The insecticide had a higher toxicity at low temperature.