Delayed behavioral responses of the blacknose dace ( rhinichthys atratulus) to chloramines and free chlorine

Abstract

1. 1. Delayed behavioral responses of the blacknose dace to chloramines and free chlorine were studied for periods up to 220 min to demonstrate the importance of time as a factor in estimating the behavioral response. 2. 2. Concentrations used were 0.07 and 0.17 mg/l as total chlorine for chloramines and 0.07, 0.21 and 0.47 mg/l for free chlorine. 3. 3. Fish avoided both chemicals at all concentrations studied. 4. 4. The latent period and median avoidance time of the fish to both chemicals decreased as the total chlorine concentration increased, and were shorter for chloramines than for free chlorine. 5. 5. The median avoidance time was shorter than the median lethal exposure time and much shorter than the median survival time. 6. 6. The results indicate the need to reference statements concerning the avoidance abilities of fish to the particular time required for such a response. 7. 7. Also, these fish have the capability to avoid chloramines and free chlorine in water before receiving a lethal dose, given the opportunity to readily find clean water.