Exposure times necessary for antimycin and rotenone to eliminate certain freshwater fish

In laboratory flowing-water troughs exposure required to induce 100% mortality, regardless of time to death for antimycin and rotenone against selected freshwater fish species was determined. Carp and white suckers required shorter exposures to antimycin (6 hr) than to rotenone (18–24 hr) at field-use concentrations of 5 and 50 ppb respectively. Bullheads were killed by 3–10 hr exposure to 100–250 ppb rotenone at 17 C or higher. However, the long exposure time necessary in colder water (25 hr at 100 ppb in 12 C water) made elimination of bullheads with rotenone difficult in cold seasons. Exposure time was influenced more by water temperature than by the toxicant concentration. The effects of rotenone were often reversible even after fish had been on their sides in the toxicant solution for 4–5 hr but irreversible for antimycin after fish showed the first signs of distress.