STUDY NUMBER : 6 . 3 ( COMPLETE ) 



ORGANIZATION ; Environmental Protection Agency (EPA) 



TITLE OF STUDY ; Chronic Bioassays of Upper Clark Fork River 

 Water 



CONTACT ( S ) ; Dick Montgomery - Environmental Protection Agency 



- 449-5486 



Loren Bahls - Montana Department of Health and 

 Environmental Sciences, Water Quality Bureau - 

 444-2406 



OBJECTIVE ; Evaluate the toxicity of upper Clark Fork River water 

 to three life stages of rainbow trout. 



DURATION: 1985 



CURRENT STATUS ; Flow-through bioassays were conducted with rain- 

 bow trout green eggs, eyed eggs and fingerlings. Test water 

 was collected from the Clark Fork River near Deer Lodge. Dilution 

 water was obtained from Taylor Creek, a nearby perennial stream. 

 A two-bank dilution system was utilized. Tests were conducted 

 from May 7 through June 6, 1985. All tests were conducted at 

 10 + 2 C. The egg tests were conducted for the full thirty 

 days. Fingerling tests were conducted for 13 days. 



The tests were timed to coincide with spring runoff, when 

 high concentrations of heavy metals are normally present in the 

 upper Clark Fork River. Normal spring runoff did not occur during 

 1985 and significant mortalities did not occur in any of the 

 tests. 



Rain events during the last half of the study produced sharp, 

 brief increases in metal concentrations. These increased con- 

 centrations exceeded calculated chronic and acute levels of copper 

 that would protect aquatic life. However, the fluctuations in 

 copper and zinc were neither high enough nor long enough in dur- 

 ation to produce significant mortalities during the test period. 



PUBLICATIONS AND REPORTS 



A Thirty-day Flow Through Bioassay Test on Copper and Zinc Tox- 

 icity in the Clark Fork River near Deer Lodge, Montana. May 

 7- June 6, 1985. Prepared by L. Parrish and Glenn Rodriguez, 

 US EPA, Region VIII, Denver, Colorado. 



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