middendorff iana reproduction was significantly impaired by 

 exposure to 100 percent pond water but not by exposure to 50 

 percent pond water (Bionomics 1979) . Copper and zinc 

 concentrations in 100 percent pond water were 3 3 and 77 ug/1, 

 respectively. Identical tests with Daphnia magna produced a 

 similar result (Bionomics 1978) ; numbers of young per female 

 were reduced by exposure to 27 ug Cu/1 and 31 ug Zn/1 

 (measured as total recoverable) . 



Janik and Melancon (1982) , during a site-specific water 

 quality assessment of Silver Bow Creek and the upper Clark 

 Fork, completed a few bioassay tests with Daphnia and 

 bluegill. In these tests, Daphnia were not adversely 

 affected by Clark Fork water nor was ventilation rate in 

 bluegill. However, bluegill in Clark Fork water showed 

 evidence of acetylcholinesterase inhibition. Total and 

 dissolved copper and zinc concentrations during the survey 

 averaged 30 and 22 ug/1 of copper and 101 and 91 ug/1 of 

 zinc. The report did not include specific information on 

 metals concentrations that were present in the bioassay 

 water. 



Parrish and Rodriguez (1986) tested the chronic toxicity 

 of Clark Fork water in the Deer Lodge vicinity to early life 

 stages of rainbow trout, including separate tests using green 

 eggs, eyed eggs, and fingerlings. Tests were conducted in 

 May and early June 1985 to coincide with runoff; however, 

 unusually dry spring conditions resulted in lower-than-normal 

 streamflows and concomitantly low metals concentrations. 

 Percentage mortality of both eyed eggs and fingerlings was 

 higher in 100 percent Clark Fork water than in various 

 dilutions, but results were not conclusive. During the test, 

 acid-soluble copper concentrations ranged from 10 to 78 ug/1. 

 For the water hardnesses that were present, EPA chronic and 

 acute criteria for copper were calculated to be approximately 

 20 and 31 ug/1, respectively. Most of the mortality occurred 

 during the last week of the tests, when copper concentrations 

 exceeded the acute criteria (weekly average concentration 

 reached 78 ug Cu/1) . 



Phillips et al. (1987) conducted in situ tests with 

 finger ling rainbow trout in the Clark Fork drainage from mid- 

 April until late July 1986. Fish were held in the river at 

 seven locations between Anaconda and Clinton, including a 

 control site in Racetrack Creek. Over the course of the 

 test, nearly 90 percent mortality occurred in Silver Bow 

 Creek, where acid-soluble copper averaged about 200 ug/1 and 

 acid-soluble zinc 400 ug/1. Cumulative mortality at mainstem 

 sites included 25 percent at Warm Springs, 15 percent at 

 Deer Lodge, 7 percent at Gold Creek, and 21 percent at 

 Bearmouth (Table 3-30) . Only 3 percent mortality occurred 

 below the confluence with Rock Creek (Clinton) . No mortality 



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