The median lethal time (LT 50) at any one initial nominal concentration of PCP tested (1.0–4.0 mg · l-1), for example 3.0 mg · l-1, is found to be longest for Tilapia mossambica (175 minutes), followed by Cyprinus carpio (50 minutes) and Rhinomugil corsula (31 minutes) suggesting that the difference in resistance (survival) to PCP may be species-specific. When R. corsula was exposed to 0.1 and 0.133 mg · l-1 PCP, the standard metabolic rate was elevated by 37 and 45% respectively at 30 °C, when compared to control fish (112 mg kg-1 hr-1). In carp, the metabolic rate showed an increase to begin with, but later decreased during the test period (20 days), but the random (spontaneous) activity was seen to slope down as the number of exposure days increased. During exercise (35 cm s-1) the rate of oxygen consumption in the control and PCP treated Tilapia decreased with the duration of exercise (5 h), but the metabolic rate in the treated fish increased considerably.