By Paul D. Schumacher, John J. Ney
Water Research, Volume 14, Issue 6, 1980, Pages 651-655, ISSN 0043-1354, DOI: 10.1016/0043-1354(80)90123-2.

Rainbow trout (Salmo gairdneri) were exposed to 20 min single-dose chlorine additions designed to achieve maximum total residual chlorine (TRC) concentrations of 0.04, 0.2, 0.6, and 1.0 mg l-1. First retreats from the chlorine front occurred at 0.05 mg l-1 TRC. Approximately 95% of the fish had moved downstream when TRC reached 0.5 mg l-1, well before cumulative time-dose exposure approached lethal limits. Percentage of fish remaining near the discharge decreased linearly as TRC concentration rose, suggesting that a rapid rise in receiving water chlorine level might be beneficial in reducing cumulative time-dose exposure. Rainbow trout demonstrated the initial sensitivity to avoid lethal chlorine exposure, but complete assessment of the utility of the avoidance response must also consider distribution throughout chlorination and the potential for repeated exposure.

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