EFFECTS OF TEMPERATURE ON VENTILATORY BEHAVIOR OF FISH EXPOSED TO SUBLETHAL CONCENTRATIONS OF ENDOSULFAN AND CHLORPYRIFOS

Abstract

The ventilation amplitude and frequency of silver perch Bidyanus bidyanus, and the ventilation frequency of rainbow fish Melanotaenia duboulayi and rainbow trout Oncorhynchus mykiss, were determined at different temperatures upon exposure to endosulfan and chlorpyrifos, respectively. Silver perch and rainbow fish were tested at 15, 20, 25, 30, and 35 degrees C, while rainbow trout was tested at 10, 15, 20, and 25 degrees C. Although some trend of increasing amplitudes with increasing temperature was evident; there was no significant temperature response of ventilation frequency rates over time in silver perch pre-exposed to 10 microg L(-1) endosulfan for 18 h. The rate of ventilation frequency of rainbow fish pre-exposed to 200 microg L(-1) of chlorpyrifos for 96 h was lower in treatments than in the control at 15 degrees C. However, between 20 and 35 degrees C, rates were significantly higher in the treatments than those of the control. In rainbow trout pre-exposed to 100 microg L(-1) of chlorpyrifos, the rates of frequency were significantly lower than those of controls in temperatures between 10 and 20 degrees C but higher at 25 degrees C. The amplitude of silver perch seemed to increase with the increase in temperature; however, the corresponding temperature quotient values at various temperature regimes and over exposure time showed no significant differences. The ventilation frequency of rainbow fish and rainbow trout significantly increased at the higher test temperatures, and their corresponding temperature quotient values for both fish also increased at the elevated temperatures.