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Reservoir and as such could only travel downstream as a result of a high 

 runoff event. As suggested by Waite and others (1980), based on patterns 

 in other reservoir flooding throughout the world, high initial mercury 

 levels in fish would be expected as a consequence of organic decay and 

 methylation of sediment-borne metal. Elevated mercury concentrations in 

 fish tissues would decline to pre-flooding background levels as organic 

 matter was assimilated. 



Mercury concentration in edible tissue of two size-classes of walleye 

 (Stizostedion vitreum) from 1979 to 1983 (Figure 24) followed the 



Figure 24. — Box plots of mercury levels in edible fish in Cookson 

 Reservoir from 1979 to 1983. Data from Water Quality 

 Branch (1980), Waite and others (1980) and Munro (1985). 

 Dashed horizontal line indicates current consumption 

 guideline of 0.5 mg/kg. 



