Test No. 204 : Fish, Prolonged Toxicity Test

This Test Guideline presents guidance for measurement of lethal and other observed effects in fish exposed to test substances. It may be used in place of Test Guideline 203 if a longer observation period is considered useful and appropriate and the reporting of additional information deemed necessary. Threshold levels of lethal and other observed effects and NOEC are determined at intervals during the test period, which is at least fourteen days. If necessary, the test period should be extended beyond 14 days by one or two weeks. The test substance should be administered to at least ten fishes for each concentration and control. One or more species may be used, the choice being at the discretion of the testing laboratory. The fish are inspected at least once a day for mortality. The study report should include the observation of lethal effects and other effects (e.g. changement in appearance, comportment of the fish), the measurements of pH, dissolved oxygen and temperature at least twice a week.