47 



2.0 n 



0.0 



Walleye 



25-35 cm 



1 



35-50 cm 



1 



o 



C=3 



White Sucker 



25-40 cm 



o 

 * * 



$^^ 



T 1 1 1 1 1 1 1 1 \ \ 1 1 1 1 



Sampling Year 



Figure 6.9 Box and Whisker Plots of Tissue Mercury Concentrations in Fish from 

 Cookson Reservoir from 1979 to 1991. Data from Water Quality Branch 

 (1980), Waite et ai- (1980), Munro (1985) and Shaw (1991, in prep). 

 Dashed horizontal indicates current Health and Welfare Canada 

 consumption guideline of 0.5 mg/Kg Hg. 



Munro (1985) also reported on several species of 'forage fish' from the Cookson 

 Reservoir, such as brassy minnow (Hybognathus hankinsoni) , Year-0 carp (Cvprinus 

 carpio) and Year-0 white suckers. Mercury burden in these three fish species ranged 

 from 0.03 to 0.25 mg/Kg. There have been no new measurements of mercury 

 concentrations in these fish species since that study. 



