Acclimation of Fathead Minnows and Lake Trout to Residual Chlorine and Bromine Chloride

Fathead minnows (Pimephales promelas) and lake trout (Salvelinus namaycush) were exposed to sublethal concentrations of total residual chlorine and bromine chloride in secondary wastewater effluent for periods of from 3 hours to 7 days. Those subjects and control fish (lacking previous exposure) were then exposed to halogen levels above their respective 96-hour ${\rm TL}_{50}$ values. Fathead minnows and lake trout with previous halogen exposure survived high halogen concentrations for longer periods than their respective controls. There was a direct relationship between acclimation time and degree of acclimation.