Variation in Results of Identical Bioassays of Minnows Subjected to Instant Temperature Increase

Abstract

Abstract Variation in the results of five near-identical bioassays of fathead minnows subjected to instant increase in water temperature is examined. It is shown that median tolerance limits for an instant temperature increase can be estimated with precision, and levels of stress tolerable to more than 50% of the test fish can be estimated with somewhat lower precision. It is suggested that the standard deviation of the population tolerance frequency distribution can be of practical value in evaluating the effect of dilution on lethality of wastes. It is concluded that TL50 values should indeed be used in calculations of “safe” levels of water quality alteration when bioassays and so called “application factors” are employed in regulating disposal of lethal agents.