1014 POLLUTION EFFECTS ON FISH
Animals whose resistance is due to enhanced abilities to
metabolize toxic substances to inactive metabolites do not,
however, contribute to biological magnification.
Biological magnification results when a foreign sub-
stance enters plants and small animals and is then passed
rapidly along food chains to larger animals. As this happens
the substance becomes more and more concentrated until it
reaches dangerous levels in the large predacious fish, many
of which are consumed by birds and mammals including
man. Clearly, the more resistance a fish has for the particu-
lar toxicant in its tissues the greater the likelihood it will
be consumed by animals living on the land. Unfortunately,
these animals may not have equivalent levels of resistance
and may be unable to adequately deal with these toxicants.CURRENT METHODS OF EVALUATING
TOXICITY IN FISHESThe establishment of water quality standards for concentra-
tions of toxic pollutants that will be safe for fish has recently
become a major concern of Federal and State Governments
in pollution control (Water Quality Criteria, 1968). Efforts in
this regard have centered around determining lethal limits of
toxicants by establishing a TLm (tolerance limit, median) of
various species exposed to toxicants for periods of time up
to 96 hr (Sprague, 1969).
These short term studies have been valuable in defin-
ing the upper limits of toxicity but have not considered the
subtle deleterious effects of foreign compounds which may
not be evident for weeks, months, or longer (Water Quality
Criteria, 1963). These responses to toxicity may manifest
themselves in appetite changes, metabolic alterations, dis-
orders of the nervous system, reproductive changes, behav-
ioral abnormalities, or alteration of vital functions which are
not immediately lethal. For this reason, investigations have
only recently been conducted to measure toxicity in terms of
survival, growth, and reproductive alterations resulting from
long-term exposure to sublethal levels of pollutants (Water
Quality Criteria, 1968). The concept of a “maximum accept-
able toxicant concentration (MATC)” has originated from
these studies and is defined as the highest continuous con-
centration of a toxicant that does not significantly decrease
the laboratory fish production index; an index developed by
Mount and Stephen (1967) which takes into account sur-
vival, growth, reproduction, spawning behavior, viability of
eggs, and growth of fry.
Because the toxicity of most pollutants varies with water
characteristics and fish species, Mount and Stephen (1967)
proposed the use of an “application factor,” (calculated by
dividing the MATC of the 96-hr TLm value), to determine
safe concentrations of toxic pollutants which, when deter-
mined for one species of fish in one type of water, may be
applicable to other waters and other species. Studies are
currently underway to test the practicality of this approach
(Mount, 1968; Mount and Stephen, 1969).
The “application factor” approach may improve upon
present methods of estimating safe concentrations of toxicants.At best, however, this approach requires considerable time for
collection and evaluation of data and measures only the end
result of a multitude of biochemical, physiological, metabolic,
pharmacological and pathological responses to toxicants. Little
definitive information is gained concerning the mechanism
which produces the gross changes upon which the “application
factor” is based.
Because of the virtual impossibility of thoroughly assess-
ing the individual, cumulative, synergistic and antagonistic
effects of the numerous substances continually being intro-
duced into our environment, it is imperative that we know
the basic metabolic, physiologic and toxicologic responses
of fish to compounds representative of broad categories of
foreign substances. Only then will we be in a position to
predict intelligently the biological effects of toxicants and
regulate their concentrations to assure protection of this very
important biological resource. If fish toxicologists continue
to consider only the effect of a substance on the labora-
tory fish production index without understanding causative
mechanisms, they will severely limit the amount of informa-
tion available for making meaningful decisions so desper-
ately needed in water pollution control programs.
Investigations of the disposition of foreign compounds
in fish will shed valuable information on the evolution of
enzymes that metabolize drugs, on drug metabolic pathways
and excretion, and on factors affecting the biological half-
life of foreign compounds in their lower species as well as
higher vertebrates including man (Adamson, 1967). The edi-
tors refer the reader to numerous studies which have noted
the collection of fishes with fin erosion or other deformities.
A few concentrated on fresh water streams (Reash and Berra,
1989; Sindermann, 1979) whereas a preponderance focused
on marine or estuarine environments with and without pol-
lution (see Cross, 1985; Skinner and Kandrashoff, 1988) for
example. Reash and Berra found that the incidence of fish
erosion was significantly greater at polluted stream sites
compared to unpolluted sites.REFERENCESAdamson, R.H. (1967) Fed. Proc., 26 , 1047.
Ashley, L.M., J.E. Halver and G.N. Wogan (1964) Fed. Proc., 23 , 105.
Brodie, B.B., G.J. Cosmides and D.P. Rall (1965) Science, 148 , 1547.
Brodie, B.B. and E.G. Erdos (1962) Proceedings of the First International
Pharmacological Meeting, 6 , Macmillan, New York.
Buhler, D.R. (1966) Fed. Proc., 25 , 343.
Conney, A.H. (1967) Pharm. Rev., 19 , 317.
Cross, J.N. (1985) Fish Bull. , 83 , 195.
Ferguson, D.E. (1967) Trans. Thirty-Second North Am. Wildlife and Natu-
ral Resources Conf.
Ferguson, D.E., D.D. Culley, W.D. Cotton and R.P. Dodds (1964) Bio
Science, 14 , 43.
Ferguson, D.E., J.L. Ludke and G.G. Murphy (1966) Trans. Am. Fish. Soc.,
95 , 335.
Forster, R.P. (1961) Kidney cells, in The Cell, Ed. by J. Brachet and
A.E. Mirshy, 5 , pp. 89–161. Academic Press, New York.
Forster, R.P. (1967) Renal transport mechanisms, in Proceedings of
an International Symposium on Comparative Pharmacology. Ed. by
E.J. Cafruny, pp. 1008–1019. Fed. Am. Soc. Expt. Biol., Bethesda,
Maryland.
Gillette, J.R. (1963) Prog. Drug. Res., 6 , 13.
Gillette, J.R. and H.A. Sasame (1966) Fed. Proc. , 25 , 737.C016_009_r03.indd 1014C016_009_r03.indd 1014 11/18/2005 1:12:30 PM11/18/2005 1:12:30 P