Measurement of Pesticide Toxicity by
Fish   Respiration Rate
ELLEN LIAW LEE, Sanitary Engineer
Warren and Van Praag
Decatur, Illinois
J. C. BUZZELL, JR., Assistant Professor
Department of Civil and Environmental Engineering
Washington University
St. Louis, Missouri
INTRODUCTION
Fish have been widely used as representatives of the aquatic community in
studies of the toxicity of waste components and other water pollutants. The acute
procedure introduced in 1945 yields an estimate of the median tolerance limit (TLm)
using death as the indicative parameter (1). The procedure is relatively simple and
has been used for screening potential pollutants and as a basis for water quality
standards (2). Attempts have been made to extend the usefulness of TLm values by
using them to estimate "biologically safe" concentrations which theoretically could
be tolerated by fish indefinitely with no significant adverse effects (3).
It is well recognized that prolonged exposure to a particular substance, even at
concentrations well below lethal levels, may produce effects which eventually decrease
the chances of survival of a species. A pollutant may produce subtle changes in an
organism which impair its ability to complete and survive (4). Because the effects
may be so insidious, it is very risky to predict that a given concentration will be truly
safe.
In order to estimate and predict the long-term effects of potentially toxic substances on fish, it has been necessary, for practical purposes, to limit the period of
testing and to focus on detectable alterations in the vehavior or physiological functions of the test specimens. Much work aimed at improving the acute toxicity
method has been done since 1945. The role of various environmental factors has
been studied and several parameters, other than death or extreme distress, have been
considered and evaluated. The size, age, species, background, etc. of the fish, as well
as various characteristics of the water, have been shown to have significant roles
(5,6). Like all bioassay procedures, technique is very important in obtaining reproducible and reliable results. Parameters used to indicate toxicity have included
such factors as changes in blood composition, respiration rate, cruising speed, feeding
and reproductive behavior, gill tissue, and several others (4,7,8). Studies involving
observations carried over more than one generation and various stages of fish life
have been carried out. Continuous-flow techniques have been developed to overcome
the shortcomings of the batch operation used in the acute toxicity method (9). The
tendencies for "internal" pollution and removal of the test substance through various
avenues in batch systems make them unsuitable for long-term studies.
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