262 



a. 



« 



s 



2000 



ISOO - 



c 



I 1000 



o 



u 



u 



soo - 



20 



Sites 1760 & 1762 



Channel Catfish 



ISOO 



30 40 SO 



Length, cm 



60 



70 



Sites 1777 & 1782 



30 40 SO 60 



Length, cm 



70 



Figure 5. Mercury concentrations in channel catfish for two regions of the St. Louis River. 

 Symbols are as follows: squares - sites 1760 and 1777, circles - sites 1762 and 1782, white - 

 1990 samples, and black - 1991 samples. 



The statistical relationships between size and age variables are given in Table V as Pearson 

 correlation coefficients (using log transformed variables) between fish mercury 

 concentrations and fish size parameters Gength, weight, and age) for each species and site 

 where sufficient data were available. In general, fish length scores slightly higher than weight 

 and significantly higher than age in correlating with mercury residue levels. The results 

 suggest a power relationship of the following form 

 (1) CHg = A*LB 



where CHg is the mercury concentration in fish, L is the fish length, and A and B are 

 constants that vary depending on fish species and body of water. This is the same expression 

 used for walleye and northern pike for 65 Minnesota lakes by Sorensen er al. (1990). 



11 



