Toxaphene was very toxic to fathead minnows (Pimephales promelas), channel catfish (Ictalurus punctatus), and bluegills (Lepomis macrochirus) in static tests; 96-h LC50's ranged from 2.6 to 20 micrograms/l at 20C. Fathead minnows were the least susceptible and bluegill and channel catfish were about equal in susceptibility. Prolonged exposures of 12 to 34 days in flow-through tests produced time-independent LC50 values of 0.6 to 1.9 micrograms/l, significantly lower than the 96-h values. The toxicity of toxaphene was not influenced by variations in pH or water hardness in static tests. Temperature seemed to influence rate of onset rather than degree of response. Toxicities were similar at 20 and 25C in flow-through tests, however, a decrease in the time required for mortality to become asymptotic with time was observed. Time-independence was reached after 7 to 16 days of exposure at 25C while 24 to 34 days were required at 20C. The life stage of channel catfish most sensitive to toxaphene poisoning was the swim-up fry with a 96-h LC50 of 0.8 micrograms/l. Early yolk sac fry were extremely resistant with a 24-h LC50 of 4.7 micrograms/l, however, within 96 hours the yolk had adsorbed and the LC50 had declined to 8.0 micrograms/l.

"January 1980." Contract No. Contract Number: EPA-IAG-141(D) Includes bibliographical references (pages 17-20).