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<br />62 HAMILTON ET AL
<br />
<br />be linked to population level effects. The present study
<br />incorporated these concerns in the experimental design
<br />by evaluating the effects on early life stages of two
<br />endangered species of an environmental mixture of
<br />inorganics found in Ashley Creek and a water quality
<br />simulating the middle Green River.
<br />Extrapolation of the results of the present study to
<br />the potential hazard in the field is a practical need in
<br />implementing the actions necessary to the recovery of
<br />endangered razorback sucker and bonytail. The most
<br />common extrapolation method is to a apply a factor to
<br />account for uncertainties in the extrapolation (Suter,
<br />1993). The uncertainty factor accounts for differences
<br />in sensitivity between species, variability of test results
<br />for one species, and extrapolation from laboratory to
<br />field (reviewed by Schudoma, 1994).
<br />For chronic toxicity tests, uncertainty factors of 10
<br />are often applied to the treatment concentration caus-
<br />ing adverse biological effect (U.S. Environmental Pro-
<br />tection Agency, 1984; Organization for Economic Co-
<br />operation and Development, 1989). In the present study,
<br />the most sensitive biological effect was reduced growth,
<br />which occurred in the 4X treatment for razorback
<br />sucker and in the 8X treatment for bonytail. Both of
<br />these treatments are less than a factor of 10 of the IX
<br />treatment, which was the mixture of inorganics at their
<br />concentrations measured in Ashley Creek. Conse-
<br />quently, it must be concluded that a high hazard poten-
<br />tial exists for adverse effects on larval razorback sucker
<br />and bony tail that might use the nursery habitats in
<br />Ashley Creek or similar habitats with elevated concen-
<br />trations of inorganic mixtures. The hazard to these
<br />larval fish is potentially higher because of the possibil-
<br />ity for adverse effects associated with dietary toxicity of
<br />inorganics and indirect effects associated with reduced
<br />growth such as reduced fitness.
<br />Another approach to assessing the hazard of chronic
<br />exposure in the present study is to calculate the
<br />acute-chronic ratio, which is the inverse of the applica-
<br />tion factor (Stephan et aI., 1985). The ratio is a way of
<br />relating acute and chronic toxicities. Using the copper
<br />concentration in the Ashley Creek mixture used in
<br />acute toxicity tests with larval stages of razorback sucker
<br />by Buhl and Hamilton (1996) of 234 JLgjL and the
<br />copper concentration in the environmental concentra-
<br />tion, i.e., IX treatment, in the present study of 10
<br />JLgjL, we derived a value of 23.4X for the acute value.
<br />In the present chronic study, the lowest treatment with
<br />adverse effects was 4X, which we use as the chronic
<br />value. Combining the two values (23.4Xj4X) gives an
<br />acute-chronic ratio of 5.8 for razorback sucker. For
<br />bonytail, the ratio was 2.0 (15.6Xj8X). Both of these
<br />values are low and indicate that the chronic toxicity
<br />observed in the present study is close, i.e., < 10, to the
<br />acute toxicity of the same mixture tested by Buhl and
<br />
<br />Hamilton (1996). These low values suggest a high haz-
<br />ard because the margin between concentrations of the
<br />mixture causing acute toxicity and chronic toxicity is
<br />small and the chronic value is close to the environmen-
<br />tal concentration. These acute-chronic ratios are simi-
<br />lar to those reported for copper and chinook salmon
<br />(> 4.5) and two fathead minnow studies (5.4 and 5.8)
<br />(U.S. Environmental Protection Agency, 1985).
<br />
<br />CONCLUSIONS
<br />
<br />Reduced survival, growth, critical swimming capacity,
<br />and behavioral changes occurred in razorback sucker
<br />and bony tail exposed to an environmental mixture of
<br />inorganics in reconstituted Green River water. These
<br />observed adverse effects may reduce the ability of
<br />larval razorback sucker and bony tail to survive through
<br />later life stages and reach maturity in the middle
<br />Green River. Comparison of biological effects concen-
<br />trations with those measured in the environment sug-
<br />gest a high hazard exists at the Ashley Creek area for
<br />the survival of the two endangered fish tested. Al-
<br />though selenium was the element of most concern in
<br />water, biota, and sediment in the NIWQP studies in
<br />the middle Green River, the present study suggests
<br />that inorganic mixtures of copper, selenium, and zinc
<br />may have contributed to the toxic effects observed.
<br />Toxic effects from inorganics associated with irrigation
<br />activities may be contributing to the decline of endan-
<br />gered fish in the middle Green River.
<br />
<br />The authors thank Dexter NFH, New Mexico, for supply-
<br />ing the fish eggs, M. Ehlers, M. Gaikowski, S. McDonald, and
<br />J. Reynolds for technical assistance in conducting the toxicity
<br />tests and chemical analyses, S. King and A. DeLonay for
<br />evaluation of behavior video tapes, W. Brumbaugh, A. De-
<br />Lonay, K. Holley, and two anonymous reviewers for providing
<br />helpful comments on this paper, and K. Faerber for typing
<br />various drafts.
<br />
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<br />
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<br />Association, and Water Pollution Control Federation.
<br />Standard Methods for the Examination of Water and
<br />Wastewater (I8th ed.); American Public Health Associa-
<br />tion: Washington, DC, 1992.
<br />Arthur, J. W. Intern J Environ Stud 1988, 32, 97-110.
<br />Atchison, G. J.; Henry, M. G.; Sandheinrich, M. B. Environ
<br />BioI Fish 1987,18,11-25.
<br />Barns, R. A. J Fish Res Board Can 1967,24,1117-1153.
<br />Beamish, F. W. H. In Fish Physiology; Hoar, W. S.; Randall.
<br />D. J., Eds.; Academic: New York, 1978; Vol. 7, pp 101-187.
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